CA2238127A1

CA2238127A1 - Truck traffic monitoring and warning systems and vehicle ramp advisory system

Info

Publication number: CA2238127A1
Application number: CA 2238127
Authority: CA
Inventors: Terry Bergan; Rod Klashinsky
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-05-15
Filing date: 1998-05-15
Publication date: 1999-11-15

Abstract

Traffic monitoring and warning and vehicle ramp advisory systems are provided herein. They include a first set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching a hazard for producing signals which are indicative of whether the vehicle is an automobile or a truck and, if it is a truck, to record and specify the configuration of the truck. A second set of sensors may be disposed in the traffic lane approaching the hazard for providing signals which are indicative of the speed of a truck traversing the second set of sensors. A
processor is provided which has a memory for storing site-specific data related both to the geometry of the hazard and to signals which have been received from the sets of sensors. A traffic signalling device is associated with the traffic lane and is disposed downstream of the first set of sensors or of the second set of sensors, the traffic signalling device being controlled by the processor. The processor is responsive to the signals from the sensors for computing an actual speed of the truck and for computing a computed maximum speed of the truck. The computed maximum speed of the truck is derived from the site-specific dimensional data and from at least the configuration of the truck, the computed maximum speed of the truck being a maximum speed for the truck of that particular configuration safely to negotiate the hazard. The processor compares the computed actual speed of the truck with the computed maximum safe speed for the truck.
Then, the processor automatically operates the traffic signalling device if the computed actual speed of the truck exceeds the computed maximum speed for the truck. The processor also discontinues operating the traffic signalling device if the computed actual speed of the truck no longer exceeds the computed maximum safe speed for the truck.

Description

(a) TITLE OF THE INVENTION
TRUCK TRAFFIC MONITORING AND WARNING SYSTEMS AND
VEHICLE RAMP ADVISORY SYSTEM
(b) TECHNICAL FIELD TO WHICH THE INVENTION RELATES
This invention relates to traffic monitoring systems for monitoring commercial vehicles.
(c) BACKGROUND ART
Many kinds of systems have been disclosed which monitor and/or control traffic.
Typically, each highway department had a command centre that received and integrated a plurality of signals which were transmitted by monitoring systems located along the highway. Although different kinds of monitoring systems were used, the most prevalent system employed a roadway metal detector. In such system, a wire loop was embedded in the roadway and its terminals were connected to detection circuitry that measured the inductance changes in the wire loop. Because the inductance in the wire loop was perturbed by a motor vehicle (which included a quantity of ferromagnetic material) passing over it, the detection circuitry detected when a motor vehicle was over the wire loop. Based on this perturbation, the detection circuity created a binary signal, called a "loop relay signal", which was transmitted to the command centre of the highway department. The command centre gathered the respective loop relay signals and from these made a determination as to the likelihood of congestion. The use of wire loops was, however, disadvantageous for several reasons.
First, a wire loop system did not detect a motor vehicle unless the motor vehicle included a sufficient ferromagnetic material to create a noticeable perturbation in the inductance in the wire loop. Because the trend now is to fabricate motor vehicles with non-ferromagnetic alloys, plastics and composite materials, wire loop systems will increasingly fail to detect the presence of motor vehicles. It is already well known that wire loops often overlook small vehicles. Another disadvantage of wire loop systems was that they were expensive to install and maintain. Installation and repair required that

2 a lane be closed, that the roadway be cut and that the cut be sealed. Often too, harsh weather precluded this operation for several months.
Other, but non-invasive, systems have been suggested. US Patent 5,060,206, patented October 22, 1991 by F. C. de Metz Sr., entitled "Marine Acoustic Aerobuoy and Method of Operation", provided a marine acoustic detector for use in identifying a characteristic airborne sound pressure field generated by a propeller-driven aircraft. The detector included a surface-buoyed resonator chamber which was tuned to the narrow frequency band of the airborne sound pressure field and which had a dimensioned opening formed into a first endplate of the chamber for admitting the airborne sound pressure field. Mounted within the resonator chamber was a transducer circuit comprising a microphone and a preamplifier. The microphone functioned to detect the resonating sound pressure field within the chamber and to convert the resonating sound waves into an electrical signal. The pre-amplifier functioned to amplify the electrical signal for transmission via a cable to an underwater or surface marine vehicle to undergo signal processing. The sound amplification properties of the resonator air chamber were exploited in the passive detection of propeller-driven aircraft at airborne ranges exceeding those ranges of visual or sonar detection to provide 44 dB of received sound amplification at common aircraft frequencies below 100 Hz. However, this patent used only a single electro-acoustic transducer for receiving acoustic signals within a detection zone, and did not teach spatial discrimination circuitry for representing acoustic energy emanating from a detection zone.
US Patent No. 3,445,637, patented May 20, 1969 by J. M. Auer, Jr., entitled "Apparatus for Measuring Traffic Density" provided apparatus for measuring traffic density in which a sonic detector produced a discrete signal which was inversely proportional only to vehicle speed for each passing vehicle. A meter, which was responsive to the discrete signals, produced a measurement representative of traffic density. However, this patent used only a single electro-acoustic transducer for receiving acoustic signals within a detection zone, and did not teach spatial discrimination circuitry for representing acoustic energy emanating from a detection zone.

3 US Patent No. 3,047,838, patented July 31, 1962 by G. D. Hendricks, entitled "Traffic Cycle Length Selector" provided a traffic cycle length selector which automatically related the duration of a traffic signal cycle to the volume of traffic in the direction of heavier traffic along a thoroughfare. The Hendricks system did not teach the use of electro-acoustic transducers, but instead used pressure-sensitive detectors.
While Hendricks employed plural, non-electro-acoustic transducers, the traffic cycle length selector system did not include spatial discrimination circuitry.
Hendricks merely described the use of the output of several spatially discriminate detectors to generate a spatially indiscriminate signal.
There are, in addition, many other patents which are directed to systems which monitor and/or control traffic. Amongst them are the following US Patents.
3,275,984 9/1966 Barker 3,544,958 12/1970 Carey et al.

3,680,043 7/1972 Angeloni 3,788,201 1/1974 Abell 3,835,945 9/1974 Yamanaka et al.

3,920,967 11/1975 Martin et al.

3,927,389 12/1975 Neeloff 3,983,531 9/1976 Corrigan

4,049,069 9/1977 Tamamura et al.

4,250,483 2/1981 Rubner 4,251,797 2/1981 Bragas et al.

4,284,971 8/1981 Lowry et al.

4,560,016 12/1985 Ibanez et al.

4,591,823 5/1986 Horvat 4,727,371 2/1988 Wulkowicz 4,750,129 611988 Hengstmengel et al.

4,793,429 12/1988 Bratton et al.

4,806,931 2/1989 Nelson

5,008,666 4/1991 Gebert et al.

5,109,224 4/1992 Lundberg 5,146,219 9/1992 Zechnall 5,173,672 12/ 1992 Heine 5,231,393 7/1993 Strickland 5,315,295 5/1994 Fujii Specifically, some of these patents simply operated regular traffic signals or warning signs. US Patent No. 4,908,616 disclosed a simple system deployed at a traffic signal controlled intersection. A warning device positioned in the approach to the intersection at a "reaction point" gave an indication to a driver as to whether or not the driver's vehicle was too close to the intersection to stop safely if the traffic signal had just changed. The system did not measure vehicle speed and cannot account for differing stopping distances for different classes of vehicle.
Systems which measure the speed of the vehicle included that disclosed in US
Patent No. 3,983,531, patented 9/1976, by Corrigan, which measured the time taken for a vehicle to pass between two loop detectors and operated a visual or audible signal if the vehicle was exceeding a set speed limit.
US Patent No. 3,544,958, patented 12/1970, by Carey, et al, disclosed a system which measured the time taken for the vehicle to traverse the distance between two light beams and displayed the measured vehicle speed on a warning sign ahead of the vehicle.
Conversely, US Patent No. 3,275,984, patented 9/1966, by Barker, disclosed a system which detected when traffic was moving too slowly, thereby indicating that a highway was becoming congested, and activated a sign near a highway exit to divert traffic via the exit.
US Patent No. 4,591,823, patented 5/1986, by Horvat, disclosed a more complicated system using radio transceivers which were located along the roadway which broadcast speed limit signals by transceivers carried by passing vehicles.
Signals returned by the vehicle mounted transceivers enabled the roadside transceivers to detect speed violations and to report them to a central processor via modem or radio.
Traffic monitoring systems have also been disclosed which monitored various parameters of the vehicle itself to enable the class of vehicle to be determined. Thus, US Patent No. 5,173,692, patented 12/1992, by Heine, disclosed a system for controlling access through a gate or entrance according to class of vehicle and which used ultrasonic detectors to detect vehicle profiles and compared them with established profiles to determine the class of vehicle.

US Patent No. 3,927,389, patented 12/1975, by Neeloff, disclosed a system which counted the number of axles on a vehicle to enable classification of the vehicle and the calculation of an appropriate tariff for use of a toll road.
Systems (known as WIM systems) were also known which used sensors to weigh 5 vehicles while they were in motion so as to detect, for example, overweight commercial vehicles. Examples of such systems are disclosed in US Patents Nos. 3,835,945, patented 9/ 1974, by Yamanaka et al. ; 4,049,069, patented 9/ 1977, by Tamamura et al. ;
4,560,016, patented 12/1985, by Ibanez et al.; and 4,793,429, patented 12/1988, by Bratton et al.
US Patent number 5,008,666, patented 4/1991, by Gebert et al., disclosed traffic measurement equipment employing a pair of coaxial cables and a presence detector for providing measurements including vehicle count, vehicle length, vehicle time of arrival, vehicle speed, number of axles per vehicle, axle distance per vehicle, vehicle gap, headway and axle weights.
Lundberg, US Patent No. 4,109,224, disclosed a system which was concerned with traffic conditions and the difficulty a driver had in assessing a safe distance to the vehicle ahead, especially when there was fog, ice or rain. Lundberg's system had a series of "cat's eyes" in the road surface which served as both signalling devices and sensors for detecting vehicle presence. The Lundberg sensors merely detected vehicle presence and the processor, using the distance between sensors, then computed the speed of the vehicle. Lundberg's system detected the speeds both of a lead vehicle and a following vehicle and used "pre-programmed rules" to determine whether or not the following vehicle was too close for its speed. If it was, the processor lighted up the cat's eyes in the road ahead to warn the driver of the following vehicle to slow down. The maximum safe speed was obtained from a table which listed several different maximum speeds for different weather conditions. Lundberg's system merely selected a maximum speed from the table regardless of the type of vehicle.
Hengstmengel, US Patent No. 4,750,129, was directed to the production of an alarm signal on the basis of data obtained only from the speed of a vehicle which actually had overtaken a slower vehicle. Consequently, speed-limited signals were only produced

6 by signal display arrangements to warn the overtaking vehicle if there was a real risk of a collision.
The known systems did not, however, deal with the fact that a particular site will not be a hazard for one type of vehicle, for example an automobile, but will be a hazard for a truck. When commercial vehicles, especially large trucks, are involved in accidents, the results are often tragic. Statistics show that, although commercial vehicles are involved in a relatively small percentage of all motor vehicle accidents, they are involved in a higher percentage of fatal accidents than other vehicles.
Consequently, they warrant special monitoring.
The invention previously made by the assignees of the present inventors provided an improved traffic monitoring system which was especially suited to monitoring commercial vehicles, namely in US Patent No. 5,617,086, patented April 1, 1997. That invention was concerned with assessing whether or not the site constituted a hazard for a particular vehicle depending upon its size, weight, speed and the like. The essence of that invention was to use a variable parameter (vehicle speed) and a fixed parameter (vehicle weight) to provide information relative to the maximum speed at which a hazard may be safely negotiated based upon the site-specific data of that hazard.
That invention was therefore concerned with the fact that a hazard (e.g., a particular curve, incline, controlled intersection, or the like) will not be a hazard for one type of vehicle, for example an automobile, travelling at a particular speed but will be a hazard for another type of vehicle, for example, a truck travelling at the same speed.
Recognizing this, that system had sensors to measure the weight and, if desired, one or more other physical parameters of the vehicle, e.g., height, number of axles or the like, and a processor for storing data specific to the site, e.g., severity of an incline, curvature and chamber of a bend, or distance from the sensors to a controlled intersection.
The processor used both the particular vehicle data and the site-specific data to compute a maximum speed for that particular vehicle safely to negotiate that particular hazard. In essence, therefore, the system used the weight and, if desired, one or other

7 more of the physical parameters of the vehicle to assess the forward momentum of that vehicle and to determine whether or not that vehicle can negotiate the hazard safely.
Several different embodiments of that invention were taught. One embodiment of that invention was directed to a traffic monitoring system which included a set of sensors which were disposed in a traffic lane approaching a hazard for providing signals indicative of the speed, and also indicative of at least the weight of a vehicle traversing the set of sensors. A processor had a memory for storing site-specific dimensional data related both to the hazard and to signals from the set of sensors. A traffic signalling device was associated with the traffic lane and was disposed downstream of the set of sensors, the traffic signalling device being controlled by the processor. The processor was responsive to the signals from the set of sensors for computing the actual vehicle speed. The processor also computed a maximum vehicle speed, which was derived from the site-specific dimensional data and from at least the weight of the vehicle. The computed maximum vehicle speed was thus the maximum speed for the vehicle safely to negotiate the hazard. The computed actual vehicle speed was compared with the computed maximum vehicle speed. The traffic signalling device was then operated if the computed actual vehicle speed exceeded the computed maximum safe vehicle speed.
Another embodiment of that invention was a traffic monitoring system for use in association with a traffic-signal-controlled intersection having a set of traffic signals and a traffic signal controller. The system included a plurality of sensors which were disposed in a traffic lane upstream of the traffic-signal-controlled intersection. The plurality of sensors included a final sensor which was disposed a predetermined distance in advance of the intersection, a preceding sensor which was disposed a predetermined distance preceding a final sensor in the direction of traffic flow, and a further sensor which sensed weight of the vehicle for providing signals indicative of the weight of the vehicle. A processor was included which had a memory for storing site-specific dimensional data including the predetermined distance. The processor was responsive to signals from the vehicle weight sensor, from the preceding sensor, and from the final sensor to compute a predicted vehicle speed at the final sensor. From the site-specific dimensional data the processor then determined whether or not the predicted vehicle speed exceeded a computed maximum speed, at which speed the vehicle can safely stop at the intersection, should the traffic signals require it. If the vehicle cannot safely stop at the intersection, the processor transmitted a pre-emption signal to the traffic signal controller, thereby causing the traffic signal controller to switch, or to maintain, the traffic signal to afford right-of way through the intersection to that vehicle.
Yet another embodiment of that invention provided a traffic monitoring system for determining potential rollover of a vehicle, The sensor comprised a set of sensor arrays which were disposed in a traffic lane approaching a curve and a vehicle height sensor. The site-specific data included characteristics of the curve, e.g., camber and curvature. The traffic signal device included a variable message sign associated with the traffic lane and which was disposed between the sensor arrays and the curve.
The processor was responsive to the signals from the sensor array for computing, as the vehicle speed, a predicted speed at which the vehicle will be travelling on arrival at the curve, and derived the maximum speed for the particular vehicle to negotiate the curve safely on the basis of vehicle parameters, including weight and height. The processor compared the predicted speed with the maximum speed and operated the traffic signal to display a warning to the driver of the vehicle if the predicted speed exceeded the maximum speed. Such a system could be deployed, for example, at the beginning of an exit road from a highway, between the highway exit and a curved exit ramp, and would warn the driver of a tall vehicle travelling so quickly that there is a risk of rollover as it attempts to negotiate the curve. In such embodiment of that invention it was necessary also to measure the height of the vehicle as it approached a curve, since the lateral momentum of the vehicle in the curve can be predicted to determine the safe speed at which the vehicle can negotiate the curve without rollover. Thus, the system of that invention computed a safe maximum speed for a particular vehicle in dependence upon, among other things, the weight and height of the vehicle.
Thus, the following systems have now been provided:
A truck rollover advisory system, which is a system designed to reduce truck rollover accidents which occur on highway exit ramps, in which in-road and off-road sensors determine individual truck speed, weight, height and type. From this real time data/information, the probability of a particular truck rolling over is computed by a controller. A warning sign is automatically activated if an unsafe configuration is detected.
A downhill truck speed advisory system, which is a variable message sign to advise individual trucks of a safe descent speed prior to beginning a long downhill grade, in which, as trucks approach the downhill grade, a controller computes individual truck weight and configuration and determines the maximum safe descent speed for that particular truck using FHWA (Federal Highway Administration) guidelines. A
variable message sign displays the safe descent speed for individual trucks.
A runaway truck signal control system, which reduces the possibility of disastrous intersection accidents resulting from a runaway truck. As trucks proceed down a slope, the speed, weight and classification of each individual truck is determined.
If the truck is travelling too fast to stop safely at the intersection downstream, a signal will be transmitted from a controller to the traffic signal lights. The lights will either hold or change to green until the oncoming truck travels through the intersection.
(d) DESCRIPTION OF THE INVENTION
While these systems have adequately addressed the problems of truck rollovers, "runaway" trucks and downhill excess speed travel for trucks, some improvements are desirable. It would therefore be desirable to provide a system which made maintenance more efficient without unduly disrupting the traffic on the roadway. Thus, the systems of the prior art as discussed above, are expensive to install and maintain.
Moreover, installation and repair require that a lane be closed, that the roadway be cut and that the cut be sealed. Often too, harsh weather can preclude this operation for several months.
The present invention provides a first embodiment of a traffic monitoring and warning system which includes a first set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching a hazard for producing signals which are indicative of whether the vehicle is an automobile or a truck and, if it is a truck, to record and specify the configuration of the truck, a second set of sensors which are disposed in the traffic lane approaching the hazard for providing signals which are indicative of the speed of a truck traversing the second set of sensors, a processor having a memory for storing site-specific dimensional data related both to the hazard and to signals which have been received from the sets of sensors, and a traffic signalling device which is associated with the traffic lane and which is disposed downstream of the 5 second set of sensors, the traffic signalling device being controlled by the processor, ~t processor being responsive to the signals from the second sets of sensors for computing an actual speed of the truck and for computing a computed maximum speed of the truck, the computed maximum speed of the truck being derived from the site-specific dimensional data and from at least the configuration of the truck, the computed 10 maximum speed of the truck being a maximum speed for the truck of the configuration safely to negotiate the hazard, the processor comparing the computed actual speed of the truck with the computed maximum of safe speed for the truck, and the processor then automatically operating the traffic signalling device if the computed actual speed of the truck exceeds the computed maximum speed for the truck, and also discontinuing operating the traffic signalling device if the computed actual speed of the truck no longer exceeds the computed maximum safe speed for the truck.
By a first variant of a second embodiment of the system of this invention, a traffic monitoring and warning system is provided comprising a first set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching a curve for producing signals which are indicative of whether a vehicle is an automobile or a truck, and if it is a truck to specify the configuration of the truck, by providing a set of signals which are indicative of the configuration of the truck, a second set of sensors which are disposed in a traffic lane approaching a curve, the second set of sensors comprising a set of sensor arrays for providing signals which are indicative of the speed of the truck, a third set of sensors for providing signals which are indicative of the height of the truck, a processor having a memory for storing site-specific dimensional data comprising characteristics of the curve and signals which have been received from the sets of sensors, and a traffic signalling device which is associated with the traffic lane and which is disposed downstream of the sets of sensors, the traffic signalling device being controlled by the processor, the processor being responsive to signals from the sets of sensors for computing an actual speed at which the truck will be travelling on arrival at the curve, and for deriving a computed maximum safe speed for the truck safely to negotiate the curve on the basis of the configuration of the truck as determined by the first set of sensors and on the basis of the height of the truck as determined by the truck height sensor, the processor comparing the computed actual speed of the truck with the computed maximum safe speed for the truck, and the processor then automatically operating the traffic signalling device if the computed actual speed of the truck exceeds the computed maximum safe speed for the truck, to display a warning to a driver of the truck if the computed actual speed of the truck exceeds the computed maximum safe speed for the truck, and also discontinuing operating the traffic signalling device if the computed actual speed of the truck no longer exceeds the computed maximum safe speed for the truck.
By a second variant of the second embodiment of the system of this invention, a traffic monitoring and warning system and vehicle ramp advisory system is provided comprising a first set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching a curve for producing signals which are indicative of whether a vehicle is an automobile or a truck, and if it is a truck to specify the configuration of the truck, by providing a set of signals which are indicative of the configuration of the truck, the first set of sensors also providing signals which are indicative of the speed of the truck, a processor having a memory for storing site-specific dimensional data comprising characteristics of the curve and signals which have been received from the first set of sensors, and a traffic signalling device which is associated with the traffic lane and which is disposed downstream of the first set of sensors, the traffic signalling device being controlled by the processor, the processor being responsive to signals from the first set of sensors for computing an actual speed at which the truck will be travelling on arrival at the curve, and for deriving a computed maximum safe speed for the truck safely to negotiate the curve on the basis of the configuration of the truck as determined by the first set of sensors, the processor comparing the computed actual speed of the truck with the computed maximum safe speed for the truck, and the processor then automatically operating the traffic signalling device if the computed actual speed of the truck exceeds the computed maximum safe speed for the truck, to display a warning to a driver of the truck if the computed actual speed of the truck exceeds the computed maximum safe speed for the truck, and discontinuing operating of the traffic signalling device if the computed actual speed of the truck no longer exceeds the computed maximum safe speed for the truck.
By a third embodiment of the traffic monitoring and warning system of this invention, the system comprises a first set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching a traffic-signal-controlled intersection for producing signals which are indicative of whether a vehicle is an automobile or a truck, and, if it is a truck, to specify the configuration of the truck, by providing a set of signals which are indicative of the configuration of the truck, a second set of sensors comprising a plurality of sensors which are disposed in the traffic lane upstream of the traffic-signal-controlled intersection having a set of traffic signals and a traffic signal controller, the second set of sensors constituting the plurality of sensors comprising a final sensor which is disposed a predetermined distance from the intersection, and a preceding sensor which is disposed a predetermined distance preceding the final sensor in the direction of traffic flow, the preceding sensor providing signals which are indicative of the speed of a truck traversing the set of sensors, and a processor for storing data including a predetermined distance, the processor being responsive to signals from the preceding sensor, to signals from the final sensor, and to signals from the electro-acoustic sensors, and to site-specific data, to compute an actual speed of the truck at the final sensor and to compute a maximum speed of the truck, and then to determine whether or not the computed actual speed of the truck exceeds a maximum speed of the truck from which the truck can safely stop at the intersection should the traffic signals require it, the processor transmitting a pre-emption signal to the traffic signal controller causing the traffic signal controller to switch, or to maintain, the traffic signal to afford right of way through the intersection to the truck in the event that the computed actual speed of the truck exceeds the computed maximum safe speed for the truck.

By a fourth embodiment of the system of this invention, a traffic monitoring and warning system is provided comprising a traffic-signal-controlled section having a set of traffic signals and a traffic signal controller, the traffic monitoring system comprising a first set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane for producing signals which are indicative of whether a vehicle is an automobile or a truck, and, if it is a truck, to specify the configuration of the truck, by providing a set of signals which are indicative of the configuration of the truck, a second set of sensors comprising a plurality of sensors which are disposed in a traffic lane upstream of the traffic-signal-controlled intersection, the second set of sensors constituting the plurality of sensors comprising a preceding sensor which is disposed a predetermined distance in advance of the intersection and a final sensor which is disposed downstream from the preceding sensor in the direction of traffic flow, for providing signals which are indicative of the speed of a vehicle, and a processor having a memory for storing site-specific dimensional data including the predetermined distance, the processor being responsive to the signals from the truck configuration sensor, from the preceding sensor and from the final sensor to compute predicted actual speed of the truck at the final sensor, and for computing a maximum safe speed for the truck and being responsive to signals from the site-specific dimensional data to determine whether or not the predicted speed of the truck exceeds the computed maximum safe speed of the truck at which speed the truck can safely stop at the intersection curve, the processor then transmitting a pre-emption signal to the traffic signal controller, thereby causing the traffic signal controller to switch the traffic signal, or to maintain the traffic signal, to afford right of way through the intersection to the truck.
By a fifth embodiment of the traffic monitoring and warning system of this invention, the system comprises a first set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching a downgrade for producing signals which are indicative of whether a vehicle is an automobile or a truck, and if it is a truck, to indicate the configuration of the truck, for providing a set of signals which are indicative of the configuration of the truck, a second set of sensors which are spaced-apart along a traffic lane approaching the downgrade, the second set of sensors providing signals which are indicative of the speed of truck, a processor having a memory for storing site-specific dimensional data related both to the downgrade including the length and severity of the downgrade and to signals from the sets of sensors, and a traffic signalling device associated with the traffic lane and disposed downstream of the sets of sensors, the traffic signalling device comprising a message sign, the message sign being controlled by the processor, the processor being responsive to the signals from the sets of sensors for computing a computed actual speed of the truck and for computing a computed maximum safe speed for the truck which is derived from the site-specific dimensional data and from at least the configuration of the truck, the computed maximum speed of the truck being a maximum safe speed for the truck safely to descend the downgrade, the processor, by comparing the computed actual speed of the truck with the computed maximum safe speed for the truck, only operating the message sign if the computed actual speed of the truck exceeds the computed maximum safe speed for the truck by transmitting a control signal to the message sign, thereby causing the message sign to display the maximum speed for a period of time during which the sign is visible to a driver of the truck.
By two variants of the system of this aspect of the invention, a signal for discontinuing operating the traffic signalling device is based on a timer which is responsive to natural deceleration of the speed of the truck upon the driver of the truck acting on a warning provided by the traffic signalling device; or a signal for terminating display of the warning provided by the traffic signalling device comprises a downstream set of truck presence detectors and truck speed sensors, the downstream at truck presence detectors and truck speed sensors being situated downstream of the message sign, the downstream set of truck presence detectors being connected to the processor, the processor being responsive to a signal from the downstream set of truck presence detectors and truck speed sensors. By one variation of these variants of this aspect of the invention, the downstream set of truck presence detectors comprises a set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching a hazard for producing signals which are indicative of the speed of a truck traversing the set of sensors.

By another variant of the system of this aspect of the invention, the traffic monitoring system includes a weigh-in-motion scale for supplementing the set of signals which are indicative of the configuration of the truck with signals which are indicative of the actual weight of the truck.
5 By a variant of the third embodiment of the system of this invention, the second set of sensors comprises a set of electro-acoustic sensors which are disposed above a traffic lane approaching a curve for producing signals which are indicative of whether a vehicle is an automobile or a truck, and if it is a truck to specify the configuration of the truck, by providing a set of signals which are indicative of the configuration of the 10 truck, the second set of sensors also providing signals which are indicative of the speed of the truck.
By a variant of this fifth and sixth embodiments of the invention, the traffic monitoring system includes a third set of sensors which is disposed between the first set of sensors and the second set of sensors.
15 By yet a further variant of the embodiment of this invention, the traffic monitoring system includes a first sub-system of the second set of sensors which comprises above-road electro-acoustic sensors and at least one of presence sensors which is either an inductive loop, or a sonic detector; axle detectors which are either piezoelectric, capacitance, or fibre optic detectors; and height detectors which are either a laser, or a lightbeam.
By a variant of the fifth and sixth embodiments of the system of this invention, each of the second and third sets of spaced-apart sensor sub-systems comprises axle detectors, which are either piezoelectric, capacitance or fibre optic.
By yet another variant of the fifth and sixth embodiments of the system of this invention, the preceding sensor comprises first and second sensor arrays which are spaced apart along the traffic lane, the processor being responsive to the data and to signals from the first and second sensors for computing the maximum safe speed of the truck and being responsive to the signals from the final sensor array for determining the actual speed of the truck at the final sensor.

By still another variant of the fifth and sixth embodiments of the system of this invention, the second set of sensors comprises first, second and third sensor arrays which are spaced apart along a traffic lane upstream of a traffic-signal-controlled intersection having a set of traffic signals and a traffic signal controller, the set of sensors each S including sensors for providing signals in dependence upon at least one physical parameter of the truck which is different from the length of the truck and the number and configuration of axles of the truck, the processor storing site-specific date including distances between the first and second sensor arrays, and between the third sensor array and the intersection, and the processor being responsive to the site-specific data and to signals from the second sensor array for computing a maximum safe speed for the truck, and being responsive to signals from the third sensor array for computing actual speed of the truck at the third sensor, the processor comparing the speed at the third sensor array with the computed maximum safe speed for the truck and, if the speed at the third sensor array exceeds the computed maximum safe speed of the truck, then the processor transmits a signal to the traffic signal controller, thereby causing the traffic signal controller to switch, or to maintain, the traffic signal to afford right of way through the intersection to the truck.
By yet a further variant of the fifth and sixth embodiments of the system of this invention, the traffic monitoring system further includes a camera device which is actuatable in dependence upon a selected signal to capture an image of a truck causing the selected signal. By a variation thereof, the traffic monitoring system further includes a vehicle presence detector downstream of the camera device for generating a signal, when traversed by the truck, for deactivating the camera device.
By other variants of the embodiments of the systems of this invention and the variants and variations thereof, the set of electro-acoustic sensors comprises a first electro-acoustic sensor for receiving a first acoustic signal which is radiated from the truck at a predetermined zone and for converting the first acoustic signal into a first electric signal that represents the first acoustic signal, a second electro-acoustic sensor for receiving a second acoustic signal which is radiated from the truck at the predetermined zone and for converting the second acoustic signal into a second electric signal that represents the second acoustic signal, spatial discrimination circuitry for creating a third electric signal which is based on both the first electric signal and on the second electric signal, that substantially represents the acoustic energy emanating from the predetermined zone, frequency discrimination circuitry for creating a fourth signal which is based on the third signal, and interface circuitry for creating an output signal which is based on the fourth signal such that the output signal is asserted when the truck is within the predetermined detection zone and whereby the output signal is retracted when the truck is not within the predetermined detection zone. By one variation thereof, the frequency discrimination circuitry comprises a bandpass filter. By another variation thereof, the frequency discrimination circuitry comprises a bandpass filter with a lower passband edge substantially close to 4KHZ and an upper passband edge substantially close to 6KHz.
By still other variants of the embodiments of the systems of this invention and the variants and variations thereof, the electro-acoustic sensors comprise a plurality of electro-acoustic sensors which are trained on a predetermined zone, a bandpass filter for processing electrical signals from the plurality of electro-acoustic sensors, a correlator having at least two inputs and an output for correlating filtered versions of the electrical signals originating from at least two of the plurality of electro-acoustic sensors, an integrator for integrating the output of the correlator means over time, and a comparator for indicating detection of the truck when the integrated output exceeds a predetermined threshold. By one variation thereof, the system further includes a plurality of analog-to-digital convertors for converting the electrical signals to digital representations prior to the processing thereof. By another variation thereof, the integrator and the comparator are each microprocessor-based programs. By yet another variation thereof, the plurality of electro-acoustic sensors comprises two vertical and two horizontal multiple-microphone elements, and the correlator means has one of the at least two inputs receiving a sum of the two multiple-microphone vertical elements, and the other of the at least two inputs receiving a sum of the two horizontal multiple-microphone elements.
By another embodiment of this invention, a first embodiment of a method is provided for automatically controlling the operation of a traffic signalling device associated with a hazard by analyzing data from any of the systems described above, comprising the steps of: downloading a set of records of parameters of the specific truck and associated speeds derived from a set of sensors which are disposed upstream of the hazard into a processor, downloading a set of records for corresponding parameters of the specific truck and speeds derived from a set of sensors which are disposed downstream of the hazard into the processor, matching records, by the processor, of the specific truck from both sets of records, computing, by the processor, from the records, an actual speed of the specific truck and a computed maximum safe speed for the truck, comparing, by the processor, an actual speed of the truck the computer maximises safe speed for the truck, automatically operating, by the processor, the traffic signalling device if the computed actual speed of the truck exceeds the computed maximum safe speed of the truck, to display a warning to a driver of the truck when the computed actual speed of the truck exceeds the computed maximum speed of the truck, and discontinuing, by the processor, operating the traffic signalling device if the computed actual speed of the truck no longer exceeds the computed maximum safe speed for the truck.
By another embodiment of this invention, a second embodiment of a method is provided for automatically controlling the operation of a traffic signalling device associated with a curve by analyzing data from any of the systems as described above, comprising the steps of downloading a set of records of parameters of the specific truck, including the height of the specific truck, and associated speeds derived from a at least two sets of sensors which are disposed upstream of the hazard into a processor, matching records, by the processor, of the specific truck from both sets of records, computing, by the processor, from the records, an actual speed of the specific truck and a computed maximum safe threshold speed for the truck from rollover threshold data which has been downloaded from the processor, calculating, by the processor, an anticipated speed of the truck at the point of curvature of the curve, automatically operating, by the processor, the traffic signalling device if the computed actual speed of the truck exceeds the computed maximum safe threshold speed of the truck, to display a warning to a driver of the truck when the computed actual speed of the truck exceeds the computed maximum threshold speed of the truck, and discontinuing, by the processor, operating the traffic signalling device if the computed actual speed of the truck no longer exceeds the computed maximum safe speed for the truck.
By yet another embodiment of this invention, a third embodiment of a method is provided for automatically controlling the operation of a traffic signalling device at an intersection by analyzing data from any of the systems as described above, comprising the steps of downloading a set of records of parameters of the specific truck and associated speeds derived from at least two sets of sensors which are disposed upstream of the hazard into a processor, matching records, by the processor, of the specific truck from both sets of records, computing, by the processor, from the records, an actual speed of the specific truck and a computed maximum stopping distance for the truck from stopping threshold data which has been downloaded into the processor, downloading, into the computer, the actual speed of the truck at a premeasured distance upstream from the traffic signalling device, determining, by the processor, whether the truck will be able to stop before the traffic signalling device, and from the determination, sending, by the processor, a signal to the traffic signalling device to pre-empt the traffic signalling device.
By a variation of these embodiments of methods of this invention, the method includes the step of downloading a set of records of the actual weight of the truck. By another variation thereof, the discontinuing step is carried out by a signal which is based on a timer which is responsive to natural deceleration of the truck if a driver of the truck acts on the warning which was provided by the traffic signalling device, thereby to restore a default message to the traffic signalling devices. By yet another variation thereof, the discontinuing step is carried out by a signal which is based on an actual measured speed of the truck at the point of curvature of the curve, thereby to restore a default message to the traffic signalling device.
By a variation of the third embodiment of the method of this invention, the method includes the step of addressing a video system to record truck passage at the traffic signalling device.

By another aspect of this invention, a further method is provided for detecting and signalling the presence of a truck in a predetermined zone, the method comprising the steps of receiving, with a first electro-acoustic sensor, a first acoustic signal which is radiated from a motor vehicle and converting the first acoustic signal into a first electric 5 signal that represents the first acoustic signal, receiving, with a second electro-acoustic sensor, a second acoustic signal which is radiated from the motor vehicle and converting the second acoustic signal into a second electric signal that represents the second acoustic signal, creating, with spatial discrimination circuitry, a third electric signal, which is based on the sum of the first electric signal and the second electric signal such that the 10 third signal is indicative of the acoustic energy emanating from the detection zone, creating, with interface circuitry, a binary loop relay signal which is based on the third electric signal such that the loop relay signal is asserted when the motor vehicle is within the detection zone and such that the loop relay signal is retracted when the motor vehicle truck is not within the detection zone, and comparing the third electric signal to electrical 15 signals from known trucks to determine whether the motor vehicle is a truck, and to compute the speed of the truck, and to compute and specify the configuration of the truck, including length, number of axles, spacing of axles and height.
By yet a further embodiment of this invention, a still further method is provided for detecting trucks moving through a predetermined zone, comprising the steps of 20 training a plurality of electro-acoustic sensors on the predetermined zone, filtering electrical signals from the plurality electro-acoustic sensors, correlating at least two of the filtered electrical signals with one another, integrating the results of correlation in the immediately-preceding step over time, comparing the integrated result of t~e immediately-preceding step to a predetermined threshold and indicating detection of~ a motor vehicle when the threshold is exceeded by the integrated result, and comparing the third electric signal to electrical signals from known trucks to determine whether the motor vehicle is a truck, and to compute the speed of the truck and to compute and specify the configuration of the truck, including length, number of axles, spacing of axles and height.

By one variation thereof, the method further includes the step of converting the electrical signals to digital representations prior to the filtering. By another variation thereof, the steps of integrating and comparing are each computational routines. By yet another variation thereof, the plurality of electro-acoustic sensors comprises two vertical and two horizontal multiple-microphone elements, and the correlating step continuously correlates the sum of the two vertical multiple-microphone elements with sums of the two horizontal multiple-microphone elements.
(e) DESCRIPTION OF THE FIGURES
In the accompanying drawings:
FIG. 1 illustrates a first embodiment of the invention comprising a traffic monitoring system installed upstream of a hazard for advising a driver of a detected truck of a safe speed for the truck;
FIG. 2 is a block schematic diagram of the system of FIG. 1;
FIG. 3 is a flowchart depicting the operation of a first processor unit of the system of FIG. 2;
FIG. 4 is a flowchart depicting the operation of a second processor unit of the system of FIG. 2;
FIG. 5 is a flowchart depicting the subsequent processing of vehicle records for an optional embodiment of the system of FIG 3;
FIG. 6 illustrates first version of a second embodiment of the invention comprising a truck monitoring system installed upstream of a curve, for monitoring for potential rollover of trucks negotiating the curve;
FIG. 7 is a simplified block schematic diagram of the system of FIG. 6;
FIGS. 8A and SB are flowcharts depicting the operation of the system of FIG.
6;
FIG. 9 illustrates second version of a second embodiment of the invention comprising a truck monitoring system installed upstream of a curve of an off ramp as a vehicle ramp advisory system to help prevent rollover accidents and out of control vehicles on sharp curves of freeway off ramps;
FIG. 10 is a simplified block schematic diagram of the system of FIG. 9;

FIGS. 11A and 11B are flowcharts depicting the operation of the system of FIG. 8;
FIGS. 12 and 13 illustrate a third embodiment of the invention in the form of a traffic monitoring system installed upstream of a traffic-signal-controlled intersection and operable to pre-empt the traffic signals;
FIG. 14 is a simplified block schematic diagram of the system of FIGS. 12 and 13;
FIGS. 15A and 15B are flowcharts depicting operation of the system of FIGS. 12 and 13;
FIG. 16 is a side elevational view of the mounting of electro-acoustic sensor array sensors forming essential elements of the systems of embodiments of the present invention;
FIG. 17 is a drawing of an illustrative embodiment of an electro-acoustic sensor array constituting an essential element of the systems of the present invention as it is used to monitor the presence or absence of a truck in a predetermined detection zone;
FIG. 18 is a drawing of an illustrative microphone array as can be used in the illustrative embodiments of an electro-acoustic sensor array sensor constituting an essential element of the systems of embodiments of the present invention;
FIG. 19 is a block diagram of the internals of an illustrative detection circuit as shown in FIG. 17;
FIG. 20 is a detailed block diagram of a preferred embodiment of the electro-acoustic sensor array sensor constituting an essential element of the systems according to embodiments of the present invention; and FIG. 21 is a flow chart showing the operation of the controller block shown in FIG.20.
(f) AT LEAST ONE MODE FOR CARRYING OUT THE INVENTION
(i) DYNAMIC DOWNHILL TRUCK SPEED WARNING SYSTEM
A generic aspect of the invention will now be described with reference to FIGS.
1 through 5. This generic aspect comprises a warning system which is installed at the approach to a hazard, whether it be a curve, an incline, a blind intersection, a traffic-signal controlled intersection, etc.
Referring to FIGS. 1 and 2, the hazard warning system comprises, at a first sensor station, a truck classification system comprising a set of electro-acoustic sensors 1711,(namely, 1711A, 1711B) for classifying trucks by means of signals in dependence upon the length of the truck and the number and arrangement of axles of the truck. The electro-acoustic sensors can determine whether the detected vehicle is a truck, or is not a truck, by an analysis of the sounds emanating from the detected vehicle. In addition, the length of the vehicle can be determined by the length of time between the beginning of the detection of the vehicle and the ceasing of detection of the vehicle in its traversing through the detection zone of a known length. Finally, the speed of the vehicle can be determined by the length of time for the vehicle to traverse the detection zone of a known length. The hazard warning system also comprises a first pair of sensor arrays 12,13 -which may be of the type which are embedded in a roadway surface in the left-hand and right-hand traffic lanes, respectively. The sensor arrays 12,13 comprise vehicle presence detectors, and direct axle sensors which may comprise piezo-electric Class 1 sensors, or inductive loop presence detectors. Each of these sensor arrays 12, 13 may be used to determine the speed of the detected vehicle by the length of time for the detected vehicle to traverse the detection zone of a known length. While these are preferred, suitable alternative sensors and detectors could be used, e.g., those disclosed in the patents cited in the introduction of this specification.
On-scale detectors (not shown) may be incorporated in each lane adjacent to each of the sensor arrays 12,13. The on-scale detectors ensure that the trucks passing over the in-road sensor arrays 12,13 are fully within the active sensor zone of the sensor and are not straddling a lane. The on-scale detectors effectively eliminate the possibility that a truck which was improperly classified will receive a message recommending a speed that is higher than is safe for that particular truck.
The electro-acoustic sensors 1711 also assure that errors incurred by a truck straddling a lane do not affect the safe speed calculation. Therefore, such on-scale detectors and/or such electro-acoustic sensors are important features of the downhill speed warning system of this embodiment of the present invention.
A short distance downstream from the sensor arrays 1711A, 1711B, 12, 13, two traffic signal devices, in the form of electronic, variable message signs 14,15, are positioned adjacent respective left-hand and right-hand traffic lanes. The sensor arrays 1711A, 1711B ,12,13 and the electronic message signs 14,15 are connected to a first programmable roadside controller 16, which is conveniently located nearby. The programmable roadside controller 16 comprises a microcomputer which is equipped with interfaces for conditioning signals from the sensors, and an interface for transmitting a control signal to the respective message sign 14, 15 for the lane in which the vehicle is travelling. The microcomputer is preprogrammed with hazard site-specific software and data, i.e., specifically related to the location of the sensors 1711A,1711B, 12, 13 and the characteristics hazard, and truck classification data. It processes the signals from the sensor arrays and determines, for each truck, information including, but not limited to, number of axles on the truck, distance between axles, bumper-to-bumper vehicle length, vehicle speed and lane of travel of the truck. From the data derived from the sensors 1711A, 1711B, it then determines truck class, i.e., based upon number of axles and their spacings. Using the hazard site-specific information and the truck information, the microcomputer computes an appropriate safe speed based on, inter alia, the class of the truck, and transmits a corresponding signal to the appropriate message sign 14,15 causing it to display the safe speed while the truck passes through the region in which the sign can be viewed by the driver of the truck. The duration of the message is based upon hazard site-specific geometrics and varies from site to site.
The microcomputer creates a truck record and stores it in memory, with the recommended safe speed, for subsequent analysis.
If the system cannot classify the truck accurately, e.g., when a truck misses some of the sensors by changing lanes, the system will not display a recommended speed. In such case, the variable message sign will display a default message, e.g., "Drive Safely".
The default message is user-programmable, allowing alternative messages to be substituted.

Downstream of the electronic message signs 14,15 is a second set of sensors 1711,(namely, 1711C, 1711D,) and sensor arrays 17,18, which are the same as the first set of sensors 1711 (namely, 1711A, 1711B) and sensor arrays 12,13, and so need not be described further.
5 These second set of sensor arrays 1711(namely, 1711C, 1711D), 17, 18, are provided in conjunction with respective lanes of the roadway approximately one kilometre (0.6 mile) beyond the variable message signs 14,15. These second set of sensor arrays 1711( namely, 1711C,1711D), 17, 18, are coupled to a secondary roadside controller 19 to form a secondary sub-system. This secondary sub-system collects the 10 same information as the primary sub-system, but it is used only for monitoring the effectiveness of the primary system.
As seen in FIG 2, the roadside controllers 16 and 19 are equipped with modems 20,21, respectively, enabling remote retrieval of their truck record data, via a telephone system, by a central computer 23 in a central operations building (not seen).
15 Programmable controller 16 includes an AC or DC power line 16A, which is connected to an UPS 16B and to a power source 16C. Programmable controller 16 also includes a monitor 16D and a keyboard 16E. Likewise, programmable controller 19 includes an AC or DC power line 19A, which is connected to an UPS 19B and to a power source 19C. Programmable controller 19 also includes a monitor 19D and a keyboard 19E.
20 Each controller 16, 19 may also have an interface or communications port enabling the truck records to be retrieved by, for example, a laptop computer. The system may also allow system operators to have full control over the primary sub-system 1711 (namely, 1711C, 1711D), 12, 13, 16, including a disabling function and the ability to change the message on the variable message signs. The remote computer also has data analysis 25 software providing the ability to take two data files (one from the primary sub-system and another from the secondary sub-system) and to perform an analysis on the compliance of the truck operator to the variable sign messages. Specific truck records from the two sub-systems can be matched, and reports can be generated on the effectiveness of the speed warning system.

The sequence of operations as a vehicle (namely, a truck) is processed by the system is depicted in the flowcharts shown in Figures 3 and 4, and subsequent analysis in the flowchart of Figure 5. For convenience of description, it will be assumed that the vehicle is in the left-hand lane. It will be appreciated, however, that the same process would apply to a vehicle in the other lane. Referring first to Figure 3, which depicts operation of the primary roadside controller 16, when a vehicle passes under vehicle electro-acoustic sensors 1711A and over sensor arrays 12, the microcomputer receives a vehicle detection signal, step 3.1, and confirms, in decision step 3.2, whether or not the vehicle has been detected accurately. If it has not, step 3.3 records an error. If the vehicle has been detected accurately, and if no weigh-in-motion scale is present, a typical weight and configuration of the truck is assumed. The microcomputer creates a truck record containing this information, namely, axle spacings and number of axles, length and electro-acoustic data, together with the time and date at step 3.4. If a weigh-in-motion scale (WIM) is present at 3.31, the actual weight, as well as other information, namely, axle spacings and number of axles, length and electro-acoustic data, together with the time and date is recorded at step 3.32. Comparing the information with truck classifications stored in its memory, the microcomputer determines in step 3.5 whether or not the vehicle is a truck. If it is not, no further action is taken, as indicated by step 3.6. If it is a truck, step 3.7 conducts a speed comparison of the actual speed with a nominal recommended speed, and accesses a truck class specific speed table to determine, for that truck class, a recommended safe speed for that truck safely to negotiate the hazard. In step 3.8, the microcomputer conveys a corresponding signal to variable message sign 14 which displays a "WARNING" message. The truck driver is expected to gear down and to take due action as regard to nature of the hazard. Once the truck passes the variable message sign 14, steps 3.9 and 3.10 restore the variable message sign to the default message. The default restoration signal may be generated when the truck triggers a subsequent termination sensor (not shown), or a timer "times-out" after a suitable time-out interval. Step 3.11 stores the truck record, including the recommended speed, in memory for subsequent retrieval, as indicated by step 3.12, using a floppy disc, via modem, a laptop or any other suitable means of transferring the data to the central computer for subsequent analysis.
After passing through part of the distance to the hazard, the truck passes the region of the second set of sensor arrays, e.g., sensor 1711C, and sensor arrays 17, and the secondary roadside controller 19 receives a vehicle presence signal, as indicated in step 4.1 in Figure 4. The secondary programmable roadside controller performs an abridged set of the operations which were carried out by the primary roadside controller 16. Thus, following receipt of the vehicle presence signal in step 4.1, it determines in step 4.2 whether or not the truck was accurately detected. If it was not, step 4.3 records an error. If it was, in step 4.4, the signals from the sensor 1711C and from the sensor arrays 17 are processed to produce a secondary truck classification record, e.g., axle spacings, number of axles, weight, if available, length, speed and other electric-acoustic data, together with the time and date. Using this information, and truck classification data which are stored in memory, step 4.5 determines whether or not the vehicle is a truck. If it is not, no further action is taken, as indicated by step 4.6. If it is a truck, step 4.7 stores the vehicle record in memory. As in the case of the primary controller 16, the truck records can be downloaded to a floppy disc, a laptop computer which is connected via a suitable port, or via a modem to the central computer, for subsequent analysis to determine the effectiveness of the system.
Figure 5, shows an optional flowchart for the analysis by the central computer, but only if a weigh-in-motion scale (WIM) is present. If such weigh-in-motion scale (WIM) is present, truck records are downloaded in step 5.1 from both programmable controllers 16 and 19 and are compared in step 5.2 to match each primary truck record from the primary controller 16 with a corresponding secondary truck record, i.e. for the same truck, from the secondary controller 19. The comparison is based on time, number of axles, axle spacings and length of truck. A file is then created containing the primary truck record number from the primary controller 16, the truck secondary record number from the secondary controller 19, date and time from the primary controller, the speed of the truck as measured by the primary controller, the recommended speed, and the speed of the truck as measured by the secondary controller. Displaying or printing the matched records, as in step 5.3, enables a comparison to be made between the speed of the truck when it traversed the first set of sensor arrays 12, and sensor 1711A and its speed when it traversed the second set of sensor arrays 17, and sensor 1711C.
Step 5.4 determines the percentage of trucks which decreased speed as advised.
The generic hazard truck speed warning system as described above, is not intended to replace runaway truck ramps, but to complement the ramps and potentially decrease the probability of required use of these ramps.
(ii) ROLLOVER WARNING SYSTEM
A first variation of a second embodiment of the invention, the rollover warning system, for detecting potential rollover of a truck approaching a curve, will now be described with reference to FIGS 6 through 8B. Figure 6 shows the components of a traffic monitoring system deployed between an exit 60 of a highway 61 and a curved ramp 62 of the exit road 63. The system comprises a first set of above-road electro-acoustic sensor arrays 1711E and a first set of in-road sensor arrays 64, 65, namely station # 1 sensor array 64 and station # 2 sensor array 65, which are spaced apart along the left hand lane of the exit road upstream of the curve 62. The exit road has two lanes and a duplicate set of sensors 1711 (namely, 1711F), 64A, 65A, 66A, and a traffic signal device 68A are provided for the right hand lane. Since the operation is the same for both sets of sensors, only the set in the left hand lane will be described further.
Sensors 1711 (namely, 1711E) comprise electro-acoustic sensors which are similar to those used in the first embodiment. Sensor arrays 64, 65, which comprise vehicle presence detectors and axle sensors, are similar to those used in the first embodiment, and are spaced downstream from sensors 1711 (namely, 1711E). A height detector 67, 67A is positioned alongside the left hand lane. The height detector 67 may comprise any suitable measuring device, e.g., a laser or other light beam measuring device.
A traffic signal device, in the form of an electronic message sign 68, 68A, is disposed downstream from sensor arrays 65, 65A, and is associated with the respective left hand traffic and right hand traffic lanes, for example above it or adjacent to it.
Referring now to Figure 7, the station # 1 sensors (1711E), the station # 2 sensors (64), the station # 3 sensors (65), the overheight detector 67 and the electronic message sign 68 are connected to a roadside controller 69 which comprises the same basic components as the roadside controller of the first embodiment described above, including a microcomputer and a modem 70. The microcomputer contains software and data for processing the sensor signals to give vehicle class based on vehicle length, number of axles and axle spacings, and vehicle speed. The microcomputer is preprogrammed, upon installation, with data specific to the site, e.g., camber and radius of the curve, and the various distances between the sensor arrays and the curve. In use, the processor uses the site-specific data, and the truck-specific data derived from the sensor arrays 1711E, 64, 65, 67 to compute deceleration between the sensor arrays and predict the speed at which the truck will be travelling when it arrives at the curve 62. Taking into account height and class of the truck, and camber and radius of the curve, it determines a maximum safe speed at which that particular class of truck should attempt to negotiate the curve. If the predicted speed exceeds this maximum, implying a risk of rollover occurring, the processor activates the message sign to display a warning, e.g., SLOW DOWN! or some other suitable message. The sign is directional and is viewed only by the driver of the passing truck. The threshold speed is programmable and can be input or changed by the system user.
The sequence of operations as a vehicle is processed by the system will now be described with reference to FIGS. 8A and 8B. When the vehicle passes under electro acoustic sensors 1711E, the analysis of the sound determines whether the vehicle is a truck or is not a truck. When the vehicle passes over sensor arrays 64, 65 the resulting presence detection signal from the presence detector at sensor arrays 64, 65 is received by the processor in step 8.1 and the processor determines, in step 8.2, whether or not a vehicle has been accurately detected. If it has not, step 8.3 records an error. If the vehicle has been detected accurately, and if no weigh-in-motion (WIM) scale is present, a typical weight and configuration of the truck is assumed. The microcomputer creates a truck record containing this information, namely, axle spacings and number of axles, length and electro-acoustic data, together with the time and date at step 8.4.
On the other hand, if a weigh-in-motion (WIM) scale is present at 8.31, the actual weight, as well as other information, namely, axle spacings and number of axles, length and electro-acoustic data, together with the time and date is recorded at step 8.32. The micro computer uses this information, together with the time and date, to create a vehicle record. In decision step 8.5, from the information at steps 8.4 or 8,32, the micro computer compares the measurements with a table of vehicle classes to determine 5 whether or not the vehicle is of a class listed, specifically one of various classes of truck.
If it is not, the processor takes no further action as indicated in step 8.6.
If decision step

8.5 determines that the vehicle is a truck, however, the processor determines in steps 8.7 and 8.8 whether or not the truck was also accurately detected at sensor array 65. If not, an error is recorded in step 8.9. If it is detected accurately, the processor processes the 10 signals received from sensor 65 to compute, in step 8.10 the corresponding measurements as in step 8.4.
Station #2 may not be present in all systems, and, in such case, the system would then proceed from step 8.5 directly to step 8.14.
In step 8.14, the processor determines whether or not vehicle height is greater 15 than a threshold value (e.g., eleven feet). If the vehicle height is greater than the threshold value, the processor proceeds to step 8.15 to identify it as a particular class of truck. If the height of the vehicle is less than the threshold value, step 8.16 identifies the truck type. Having identified the truck type in step 8.15 or step 8.16, the processor proceeds to access its stored rollover threshold tables in step 8.17 to determine a 20 threshold speed for that particular truck safely to negotiate the curve. In step 8.18, the measured speed at station ~ 1 is the speed of the truck when it arrives at the beginning of the curve 62. Step 8.19 compares the predicted speed with the rollover threshold speed. If it is lower, no action is taken, as indicated by step 8.20. If the predicted speed is higher than the rollover threshold speed, however, step 8.21 activates the message sign 25 68 for the required period to warn the driver of the truck to slow down.
Step 8.22 represents the sequence of steps by the processor to process the corresponding signals from sensor array 66 to ascertain the speed of the truck and the type of truck, and to create a secondary record. Subsequent transmission of the truck data derived from all three sensor arrays 64, 65, 66 to a central computer, or retrieval 30 in one of the various alternatives outlined above, is represented by step 8.23.

Sensor array 66 is optional and is for system evaluation purposes. It is positioned between the electronic message sign 68 and the curve 62 and is used to monitor whether or not the message is heeded, i.e., whether or not trucks are slowing down when instructed to do so by the message sign. The signals from its sensors are also supplied to the programmable controller 69. This sensor array 66 need only supply information to enable truck speed to be determined and so comprises a truck axle sensor and a truck presence detector which is activated when a truck enters its field. The controller 69 processes the signals from sensor array 66 to produce a secondary truck record. As before, data from the controller 69 can be downloaded to a remote computer and truck records from the first and second sensor compared with the corresponding truck record from the third sensor to determine the speed of the truck before and after the message sign. This allows statistics to be accumulated showing the number of trucks slowing down when instructed to do so by the sign, thereby allowing evaluation of system effectiveness.
The system algorithm is site specific to accommodate certain site characteristics.
The software can be compiled on any curve site with a known camber and radius.
The data is stored on site in the programmable controller and is retrievable either by a laptop computer on site or remotely via modem communication. The controller also has an auto-calibration feature. If the system fails for any reason, an "alert"
signal is transmitted to the host computer via modem, informing the system operators of a system malfunction.
The programmable controller allows the system operator to adjust maximum allowable safe speeds, based on collected data on truck speeds at particular locations.
For example, if the maximum safe speed is set at the posted speed limit, but if the majority of trucks are exceeding the posted speed limit at a particular location, then the variable message warning sign would be excessively activated, and the system would lose its effectiveness. Therefore, it is desirable to adjust speed threshold parameters to increase system effectiveness. The centre of gravity for each truck is estimated from the rollover threshold tables.

As an option to the main classification and detection sensors, on-scale detectors may be incorporated into each lane to ensure that the trucks passing the sensor arrays are fully within the active zone of the system, and are not straddling a lane. The on-scale detectors effectively eliminate the possibility that a truck will receive a message for a S speed that is higher than is safe for that particular truck.
The electronic message sign conveniently is installed directly below a traditional information sign (e.g., a "danger ahead" sign with the image of a truck rolling over) which indicates the ramp advisory speed. The message sign is not a continuous beacon which flashes continuously. Rather, it is a sign which is activated only when a truck is exceeding the rollover threshold speed at a particular curve. A message for a specific truck is more effective, since the sign is an exception to regular signing and not a common background feature.
(iii) VEHICLE RAMP ADVISORY SYSTEM
A second variation of the second embodiment of the invention, the Vehicle Ramp Advisory System, for detecting potential rollover of truck approaching a curve, will now be described with reference to FIGS 9 through 11B. This second variation of the second embodiment of the invention, namely the Vehicle Ramp Advisory System (VRAS) is an intelligent transportation system which helps prevent rollover accidents and out-of-control vehicles on sharp curves, e.g., freeway exit ramps. Figure 9 shows the components of a VRAS traffic monitoring system deployed between an exit 90 of a highway 91 and a curved ramp 92 of the exit road 93. The system comprises a first set of above-road electro-acoustic sensor arrays 1711F which are directed at the left hand lane of the exit road upstream of the curve 92, as station # 1 sensors. Sensor arrays 1711F
comprise electro-acoustic sensors which are similar to those used in the first variation of the second embodiment. A typical orientation thereof will be described hereinafter in FIG.
16. The system also comprises a second set of above-road electro-acoustic sensor arrays 17116 which are directed at the right hand lane of the exit road upstream of the curve 92, as station # 2 sensors. Since the operation is the same for both sets of sensors, only the set in the left hand lane will be described further. A traffic signal device, in the form of an electronic message sign 98, is disposed downstream from electro-acoustic sensor arrays 1711F, and is associated with the left hand traffic lane, for example, above it or at an elevated height adjacent to it. The exit road has two lanes and hence a duplicate set of a traffic signal device 98A is provided for the right hand lane downstream from electro-acoustic sensor arrays 1711 G.
As an optional feature, the system may also comprises a third set of above-road electro-acoustic sensor arrays 1711H which are directed at the left hand lane of the exit road downstream of the first set of above-road electro-acoustic sensor arrays 1711E, but upstream of the traffic signal device 98E, as station # 3 sensors. Sensor arrays 1711E
comprise electro-acoustic sensors which are similar to those used in the first version of the second embodiment. In this optional feature, the system may also comprises a fourth set of above-road electro-acoustic sensor arrays 1711I, which are directed at the left hand lane of the exit road downstream of the first set of above-road electro-acoustic sensor arrays 17116 but upstream of the traffic signal device 98F, as station # 4 sensors:
Sensor arrays 1711I comprise electro-acoustic sensors which are similar to those used in the first variation of the second embodiment.
Referring now to Figure 10, the station # 1 sensors (1711F), the station # 2 sensors (17116), the station # 3 sensors (1711H), the station # 4 sensors (1711I) and the electronic message signs 68, 68A are connected to a roadside controller 99, 99B, which comprises the same basic components as the roadside controller of the first variation of the second embodiment described above. The roadside controller 99 includes a microcomputer 99B, and a modem 70. The microcomputer 99B contains software and data for processing the sensor signals to give vehicle class based on vehicle length, number of axles and axle spacings, and vehicle speed. The microcomputer 99B is preprogrammed, upon installation, with site-specific data, e.g., camber and radius of the curve, and the various distances between the sensor arrays and the curve. In use, the processor uses the site-specific data, and the truck-specific data derived from the electro-acoustic sensor arrays 1711F, 17116, 1711H, 1711I, to compute deceleration between the sensor arrays and to predict the speed at which the truck will be travelling when it arrives at the curve 92. Taking into account height and class of the truck, and camber and radius of the curve, the processor determines a maximum safe speed at which that particular class of truck should attempt to negotiate the curve. If the predicted speed exceeds this maximum, implying a risk of rollover occurring, the processor activates the message sign to display a warning, e.g., TRUCK REDUCE SPEED! or some other suitable message. The sign is directional and is viewed only by the driver of the passing truck. The threshold speed is programmable and can be inputted or changed by the system user.
More specifically, in this embodiment of the invention, the VRAS uses above-road electro-acoustic sensors, known by the trade-mark SmartSonicT"', to detect vehicles and classify them according to type. All information from the electro-acoustic sensors is processed in real time, just milli-seconds after the vehicle has passed through the detection zone. If the speed of the vehicle (as determined by the above-road electro-acoustic sensors) exceeds the posted advisory speed, and the vehicle is classified as a truck, a warning status is assigned to the vehicle. The warning status produces a trigger signal which activates the message sign. The sign is only activated for vehicles which IS are assigned a warning status and is specific to that particular vehicle.
Since the signs are only activated for particular vehicles, they are more noticeable and are more likely to achieve the desired response of vehicle speed reduction.
The VRAS is meant to complement the existing static signing by providing a warning and drawing the attention of a driver to the fact that the safe speed has been exceeded and that the vehicle should slow down to avoid a potential rollover or accident resulting from a loss of control. It should be recognized that the accuracy of the system is dependent on site conditions and traffic flow characteristics.
In one particular embodiment, the message signs are fibre optic message signs.
The station #1 sensors, station #2 sensors, station #3 sensors, station ~I4 sensors, and electronic message signs are all interlocked by suitable cables disposed within, e.g., a '/z" conduit 97. Typically, the distance between station #1 sensors 1711F and electronic message sign 98F is 250 feet, and the distance between station #2 sensors 71 G
and electronic message sign 98G is likewise 250 feet.
As will be further described with reference to Fig. 16, the above-road electro-acoustic sensors are mounted on poles.

A truck entering the system passes through the above-road electro-acoustic sensor detection zones. As noted above, the sensors are mounted on poles and are aimed at specific areas on the roadway through which the traffic will pass. Since two lanes are to be equipped at this site, sensors are installed on both shoulders. For each lane, two 5 detection zones are used. The above-road electro-acoustic sensors provide data which is processed by the controller electronics to determine a inter alia vehicle speed.
If a warning status is assigned by the system, the roadside message signs will be activated for that particular vehicle. The sign will remain on for a specified period of time, until the vehicle has passed the static sign. A single controller is used to receive 10 and process information from all of the above-road electro-acoustic sensors plus control the operation of the message signs. The electronics are compact and therefore easy to mount on the same pole that is used to mount the sensors. In one embodiment of this invention, where Station # 1 and Station #2 sensors only are used, a timer will shut off the message sign based on the time the vehicle is detected and the vehicle speed.
15 The fibre optics message sign is a highly visible roadside message sign to provide a real-time, eye-catching message to truck drivers. A simple single message fibre optic sign is used clearly to communicate to the driver. For example, the sign may contain the message:
TRUCK

SPEED
The illumination of the sign is controlled by electronics. When a warning message is necessary, the system turns the sign on so that the targeted driver sees the message. The timing of the activation and duration of the sign is controlled to give 25 optimum visibility and viewing time to the driver, while minimizing the possibility of a following driver viewing the sign in error.
The sign has a minimum of two different and adjustable intensities for day and night light levels, ensuring good visibility. Sign characters would have a minimum height of 10" and are readable from a distance of at least 500 feet under all lighting 30 conditions.

The housing of the sign preferably is aluminum alloy with a minimum thickness of 0.125". All exterior seams are preferably welded and made smooth. The entire housing is preferably made weatherproof. A rubber seal or other approved seal material would preferably be provided around the entire door to ensure a watertight enclosure.
The sign message preferably consists of fibre optic bundles which are arranged to form the required letters. Each bundle preferably consists of a minimum of fibres, ground smooth and polished at the input and output ends for maximum light transmission. Spare bundles numbering at least 5 % of the total bundles are connected to each light source for future replacement of damaged bundles.
The light source for each bundle is from two 50 watt quartz halogen lamps with at least an average 6000 hour rated life. A minimum of four bulbs preferably is provided for the entire sign. No more than 50 % of the illumination of each bundle preferably comes from a single bulb. In the event of the failure of a single bulb in a pair, the bundles continue to be illuminated at 50% of normal brightness. Alternating bundles in a sign face preferably are connected to different light sources, such that a lamp failure will affect only alternating pixels.
In another embodiment, where Station # 3 and Station # 4 sensors are used, these sensors, which determine deceleration and predict speed, can be used to turn off the sign based on that speed. In this embodiment, therefore, the operation of the message signs is controlled by the vehicle speed.
The controller electronics passes the real time vehicle information to a micro-controller. All vehicle information is stored in the memory of the controller and is retrievable manually at the controller cabinet. Data which is collected by the system includes vehicle counts, vehicle speed, and vehicle length (according to the three classification groups). The microcontroller receives and processes vehicle information to make a decision on the sign operation. If required, the controller activates and deactivates the real time warnings provided for drivers at the appropriate time.
The above-road electro-acoustic sensors are used to provide vehicle speed information. The above-road electro-acoustic sensors are mounted on a pole at a height of approximately 20 feet just off the shoulder of the road. Each sensor is directed at a particular area on the roadway. A bank of microphones in the sensor monitors the acoustic energy from the detection zone. The noise is filtered and analyzed to determine vehicle presence, type, and speed.
The system operates as a vehicle advisory system by collecting vehicle speed and classification information. The passage of vehicles is monitored in real time, and determines whether the maximum safe entrance speed for that particular vehicle is exceeded. The system triggers the roadside message sign only if a vehicle is exceeding the posted maximum speed.
Raw vehicle records will include the following data, namely, site identification, time and date of passage, lane number, vehicle sequence number, vehicle speed, and code for invalid measurement.
The sequence of events for a vehicle record and message generation is outlined as follows:
1. Vehicle Data Collection:
The operation of the VRAS is triggered by a vehicle through the above-road electro-acoustic sensors detection zone. When a vehicle passes through the detection zone, the system creates a new vehicle record to contain all of the information obtained for that vehicle. After passing through the detection zone, the controller processes the vehicle record to determine classification (length class) and speed.
2a. Warning Status Determination:
If the vehicle speed recorded during vehicle data collection is greater than the posted advisory speed, a warning status will be assigned specifically to that vehicle.
2b. A second set of sensors determines deceleration and calculated predicted speed.
3. Message sign activation:
As the vehicle continues along the roadway, the sign will be deactivated according to a timer or, according to Step 2a, if the predicted speed is now below the posted advisory speed. Thus, the message sign will only be activated when necessary.
The sequence of operations as a vehicle is processed by the system will now be described with reference to FIGS. 11A and 11B. When the vehicle passes under sensor 1711F, the analysis of the sound determines whether the vehicle is a truck or is not a truck at step 1 1. l . The processor determines, in step 11.2, whether or not a vehicle has been accurately detected. If it has not, step 11.3 records an error. If the vehicle has been detected accurately, and if no weigh-in-motion (WIM) scale is present, a typical weight and configuration of the truck is assumed. The microcomputer creates a truck record containing this information, namely, axle spacings and number of axles, length and electro-acoustic data, together with the time and date at step 11.4. On the other hand, if a weigh-in-motion (WIM) scale is present at 11.31, the actual weight, as well as other information, namely, axle spacings and number of axles, length and electro-acoustic data, together with the time and date is recorded at step 11.32. It uses this information, together with the time and date, to create a vehicle record. In decision step 8.5, from the information at steps 11.4 or 11.32, it compares the measurements with a table of vehicle classes to determine whether or not the vehicle is of a class listed, specifically one of various classes of truck. If it is not, the processor takes no further action as indicated in step 11.6. If decision step 8.5 determines that the vehicle is a truck, and that it was accurately detected, then, in step 11.14, the processor determines whether or not vehicle height is greater than a threshold value (e.g. eleven feet). If the vehicle height is greater than the threshold value, the processor proceeds to step 8.15 to identify it as a particular class of truck. If the height of the vehicle is less than the threshold value, steps 11.15 and 11.16 identify the truck class and type.
Having identified the truck type in step 8.15 or step 8.16, the processor proceeds to access its stored rollover threshold tables in step 11.17 to determine a threshold speed for that particular truck safely to negotiate the curve. In step 11.18, the measured speed at station # 1 is the speed of the truck when it arrives at the beginning of the curve 92.
Step 11.19 compares the predicted speed with the rollover threshold speed. If it is lower, no action is taken, as indicated by step 11.20. If the predicted speed is higher than the rollover threshold speed, however, step 11.21 activates the message sign 68 for the required period to warn the driver of the truck to slow down.
If the system does not include station #3 sensors, a timer determines, from the speed of the vehicle and the time lapse, to deactivate the warning sign at step 11.2b.

If the system includes station #3 sensors, the vehicle is detected by the sensors at station #3 in step 11.22. The processor determines in step 11.23 whether or not a vehicle has been accurately detected. If it has not, step 11.34 records an error. If the vehicle has been detected accurately, the microcomputer creates a truck record of the speed together with the time and date at step 11.25. If such speed is lower than the rollover threshold speed, the timer sensed deactivation of the warning sign is overridden, but step 11.26 deactivates the message sign.
Step 11.27 represents the sequence of steps by the processor to process the corresponding signals from electro-acoustic sensor arrays 1711 F and 1711 G to ascertain the speed of the truck and the type of truck, and to create a secondary record.
Subsequent transmission of the truck data derived from all three sensor arrays 64, 65, 66 to a central computer, or retrieval in one of the various alternatives outlined above, is represented by step 11.23.
The controller 99 processes the signals from all the electro-acoustic sensor arrays to produce a secondary truck record. As before, data from the controller 99 can be downloaded to a remote computer and truck records from the first and third sensors compared to determine the speed of the truck before and after the message sign. This allows statistics to be accumulated showing the number of trucks slowing down when instructed to do so by the sign, thereby allowing evaluation of system effectiveness.
As in the first variation of the second embodiment of this invention, the system algorithm is site specific to accommodate certain site characteristics. The software can be compiled on any curve site with a known camber and radius. The data is stored on site in the programmable controller and is retrievable either by laptop computer on site or remotely via modem communication. The controller also has an auto-calibration feature. If the system fails for any reason, an alert signal is transmitted to the host computer via modem, informing the system operators of a system malfunction.
The programmable controller allows the system operator to adjust maximum allowable safe speeds, based on collected data on truck speeds at particular locations.
For example, if the maximum safe speed is set at the posted speed limit, but if the majority of trucks are exceeding the posted speed limit at a particular location, then the variable message warning sign would be excessively activated, and the system would lose its effectiveness. Therefore, it is desirable to adjust speed threshold parameters to increase system effectiveness. The centre of gravity for each truck is estimated from the rollover threshold tables.
5 As an option to the main classification and detection sensors, on-scale detectors may be incorporated into each lane to ensure that the trucks passing the sensor arrays are fully within the active zone of the system, and are not straddling a lane. The on-scale detectors effectively eliminate the possibility that a truck will receive a message for a speed that is higher than is safe for that particular truck.
10 The electronic message sign , namely, TRUCK REDUCE SPEED !, conveniently is installed directly below a traditional information sign (e.g., a "danger ahead" sign with the image of a truck rolling over) which indicates the vehicle ramp advisory speed. The message sign is not a continuous beacon which flashes continuously. Rather, it is a sign which is activated only when a truck is exceeding the rollover threshold speed at a 15 particular curve. A message for a specific truck is more effective, since the sign is an exception to regular signing and not a common background feature.
(iv) TRAFFIC SIGNAL PRE-EMPTION SYSTEM
A third embodiment of the invention, the traffic signal pre-emption system, specifically a traffic signal pre-emption system which monitors truck speed at successive 20 points along a steep downgrade to determine when there is a "runaway" truck and pre empts traffic signals along the path of the runaway truck, will now be described with reference to FIGS. 12 through 15B.
The downhill speed warning system may be installed at the approach to a long, steep downhill grade, perhaps at the summit of a mountain pass. The downhill speed 25 warning system comprises a system of sensors and a programmable controller for classifying commercial vehicles, i.e. trucks, while they are in motion. Using that information and stored information which is specific to the downgrade, the system provides real-time safe descent speed calculations, and advises drivers of the safe descent speed by variable message signs, all before the truck begins to descend the downgrade.

This embodiment may also be used in conjunction with hazards at traffic-light-controlled intersections, or at blind intersections.
Figure 12 depicts a section through a steep downgrade 1202 with an intersection at the bottom. The intersection is controlled by traffic signals 1203 of conventional construction, i.e. the usual red, yellow and green lights controlled by a traffic signal controller 1402 (Figure 14). A truck 1201 is shown at the top of the downgrade. As the truck 1202 descends the downgrade, it will traverse a set of sensor arrays shown in more detail in Figure 13. As in the other embodiments, a set of sensor arrays is provided for each traffic lane. A camera 1204, whose purpose will be described hereinafter, is also provided, as is a utilities box 1205.
Each set of sensor arrays comprises sensor arrays, namely station # 1 sensors comprising truck classification sensors in the form of electro-acoustic sensors 1711J, 1711K, which are similar to those described previously, and sensor arrays 1305, 1305A, 1306 1306A, and 1307, 1307A, which are spaced apart in the road surface along the downgrade. Sensor arrays 1305, 1305A, 1306, 1306A, each comprise vehicle presence and direct axle detectors which are similar to those described previously, and are spaced 150 meters apart. Sensor array 1307 is positioned I50 meters beyond the sensor array 1305 and comprises a vehicle presence detector and a direct axle sensor.
Sensor arrays 1711 (namely, 1711J, 1711K), 1305, 1305A, 1306, 1306A and 1307, 1307A, are connected to a roadside controller 1408 similar to that of the other embodiments, including a processor and a modem 1409 (FIG 14). As shown in Figure 14, the roadside controller is connected to traffic signal controller 1401 which controls the sequence of the traffic signals 1402 and also a camera 1401 which is located adjacent the traffic signals.
As a vehicle traverses the zones of the sensor arrays, namely station #1 sensors, station ~l2 sensors and station #I3 sensors, the processor determines the truck type, and the speed, using the signals from the sensor arrays 1711(namely, 1711J, 1711K), 1105, 1306. If the vehicle is a truck, using the preprogrammed site-specific data, including site characteristics, e. g. , length and severity of the downgrade, the processor computes a maximum speed for that particular class of truck. From the signals from the sensor array 1306, 1306A, the processor determines whether or not the truck is exceeding the calculated maximum speed and whether the speed of the truck has increased significantly, or decreased, between the sensor arrays 1305, 1305A, 1306, 1306A. If the speed of the truck as it traaerses the sensor 1306, 1306A, is greater than the calculated maximum value, indicating that the truck cannot stop safely at the intersection, the processor transmits a pre-empt signal to the traffic signal controller 1401 which ensures that the traffic signals are in favour of the truck when it arrives at the intersection.
The specific sequence of operations is illustrated in FIGS. 15A and 15B. On receipt of a signal from sensor arrays 1711D, 1305, the processor determines, in steps 15.1 and 15.2, whether or not a truck has been accurately detected. If not, step 15.3 records an error. If the truck has been accurately detected, the processor processes the signals from electro-acoustic sensors 1711 (namely 1711J, 1711K), and signals from sensor arrays 1305, 1305A, 1306, 1306A, in step 15.4, to compute vehicle speed, bumper to bumper length, axle spacings and number of axles, measures or assumes the weight, and adds the time and date to the data before recording it. If the controller has problems processing any of the signals from the sensors in the sensor array, a warning or error is added to the vehicle information to indicate that the calculated values may be in error. From the vehicle information, the processor uses stored data or "look-up"
tables to determine vehicle type, based upon the length of the vehicle, the number of axles and the distance between each axle. From this classification, the processor determines, in decision step 15.5 whether or not the vehicle is a truck. If it is not, the processor takes no further action with the data, as indicated in step 15.6. If the vehicle data indicates that it is a truck, however, the processor computes, in step 15.7, a maximum safe speed for that truck based upon its configuration.
Upon receipt of a signal from second sensor 1306, 1306A, in step 15.8, the processor again determines whether or not the truck has been accurately detected (step 15.9). If it has not, a truck error is recorded in step 15.10. If the controller has problems processing any of the signals from the sensors in the sensor array, a warning or error is added to the truck information to indicate that the calculated values may be in error. If the truck has been accurately detected at sensor 96, the processor processes the signals from sensor 1306, 1306A, in step 15.11 to determine the truck speed, bumper to bumper length, axle spacings and number of axles, and measures or assumes the weight. In step 15.12, it compares the actual truck speed measured at sensor 1305, 1305A, with the actual truck speed measured at sensor 1306, 1306A. If the speed at sensor # 1 is greater than the speed at sensor # 2, the speed at sensor # 1 is used, at decision step 15.23. If the speed at sensor # 1 is not greater than the speed at sensor #
2, the speed at sensor # 2 is used, at decision step 15.22. The controller, by the use of the selected speed, obtains, from tables, a maximum stopping threshold for that truck classification. The stopping threshold will be based on standardized tables for each truck configuration.
When a signal is received from sensor array 96, the processor again checks that the truck has been detected accurately (steps 15.14, 15.15) and records an error if it has not. If it has, in step 15.16 the processor processes the signals from sensor 1711 to produce a record of to the truck speed, bumper to bumper length, axle spacings and number of axles, and measures or assumes the weight, and adds a time and date stamp as before. If the processor has problems processing any of the signals from the sensors, a warning or error is added to the truck information to indicate that the calculated values may be in error. Based on the stopping threshold information determined in step 12.13, and the truck speed measured at sensor 1307, the processor will determine in step 12.17 whether or not the truck will be able to stop before the intersection if the traffic signal requires it. If decision step 15.17 indicates that it will be able to stop, the processor takes no further action as in step 15.18. However, if decision step 15.7 indicates that it will not be able to stop, the processor sends a signal to the traffic signal controller 100 as indicated in step 15.19, causing it to pre-empt the traffic signal to keep the traffic flowing continuously in the direction the truck is travelling. The pre-emption signal will override the traffic signal sequence either to change the traffic signal to favour the passage of the vehicle or, if it is already in its favour, to ensure that the traffic signal does not change for a suitable interval. The duration of the traffic signal pre-emption is based upon site specific geometrics and varies from site to site. The central controller can also be programmed to pre-empt the traffic signal as a precautionary measure when a warning or error occurs at any or all of the sensor arrays 1305, 1305A, 1306, 1306A, 1307 and 1307A.
As before, as an option to the main detection sensors, on-scale detectors may be incorporated into each lane to ensure that the vehicles passing the sensor arrays are fully within the active zone of the system, and are not straddling a lane. The on-scale detectors effectively eliminate the possibility that a truck will receive a message for a speed that is higher than is safe for that particular truck.
It will be appreciated that there is potential for abuse, i.e. drivers deliberately causing the system to pre-empt the traffic signals. Accordingly, whenever the traffic signal controller 1401 receives a pre-emption signal, it operates the roadside camera 1403, as indicated by step 15.20, to capture an image of the vehicle which caused the pre-emption signal. The video record will provide a means of identifying vehicles for safety and regulatory purposes.
As in the case of the other embodiments, all vehicle data collected from electro-acoustic sensors 1711 (namely, 1711J, 1711K), 1305, 1305A, 1306, 1306A 1307 and 1307A can be transmitted, via modem, to a central computer for analysis at step 15.21.
In any of the embodiments of the invention, the controller may be reprogrammed with fresh data and table information, conveniently by means of, for example, a laptop computer. Moreover, instead of the data being transmitted via modem to the central computer, the data could be stored in the memory of the controller and retrieved periodically by, for example, a laptop computer. A remote terminal can be used to provide full remote control over the operation of the system, including controls, e.g., disabling the system or overriding signal pre-emption where there is a false alarm.
An advantage of traffic monitoring systems embodying the present invention is that they perform real-time computations using information specific to a particular vehicle without necessarily knowing the weight of the vehicle and information specific to a particular potential hazard to determine what message, if any, to display to the driver of the vehicle or, in the case of the traffic signal pre-emption system, whether or not to pre empt the regular traffic signal. Hence, the system recommendations are tailored to the site and the specific vehicle. Consequently, there is less likelihood of erroneous or untimely messages being displayed and hence increased likelihood that drivers will heed the messages and/or not abuse the system.
In each embodiment of the invention, the controller may also have an auto-calibration feature. If the system fails for any reason, an alert signal is transmitted to 5 the host computer via modem, informing the system operators of a system malfunction.
The set of electro-acoustic sensors 1711,(namely 1711A, 1711B, 1711C, 1711D, 1711E, 1711F, 17116, 1711H, 1711I, 1711) and 1711K) are based on an improvement on a system which is used to monitor highway traffic, and will be described more fully hereinafter with reference to FIGS 17 to 21.
10 (v) DESCRIPTION OF ELECTRO-ACOUSTIC SENSOR MOUNT
As seen in Fig. 16, the electro-acoustic sensors 1711, designated 1601A and 1601B, are mounted on a mast arm 1602. The mast arm 1602 is supported on a sensor mounting pole 1603, which includes a pole-mounted cabinet 1604. The pole-mounted cabinet houses the controller electronics of the above-road electro-acoustic sensors, 15 known by the trade-mark SmartSonicT"'. The pole mounted cabinet provides protection in a harsh outdoor environment, including protection from vandalism, rain, sleet, snow, dripping water, corrosion, hosedown, splashing water, and oil or coolant seepage. The sensor mounting pole 1604 is optionally provided with a breakaway base 1605.
Beneath the roadway or the shoulder of the roadway is an electrical junction box 1606.
20 Typically the mast arm is 10 feet long, and the sensor mounting pole is 20 feet high. The sensors are mounted on poles and are aimed at specific areas on the roadway through which the traffic will pass. Since two lanes are to be equipped at this site, sensors are installed on both shoulders. For each lane, two detection zones are used.
The above-road electro-acoustic sensors provide data which is processed by the controller 25 electronics to determine a vehicle speed.
(vi) ELECTRO-ACOUSTIC SENSORS
FIGS 17 to 21 will now be described with respect to the electro-acoustic sensors 1711, (namely 1711A, 1711B, 1711C, 1711D, 1711E, 1711F, 17116, 1711H, 1711I, 1711) and 1711K). Each motor vehicle using a highway radiates acoustic energy from 30 the power plant (e. g. , the engine block, pumps, fans, belts, etc.) and from its motion along the roadway (e.g., tire noise due to friction, wind flow noise, etc.).
While the energy fills the frequency band from DC up to approximately l6KHz, there is a reliable presence of energy from 3KHz to 8KHz. Thus an analysis of such energy enables the classification of the vehicle as a truck or as not a truck.
Fig. 17 depicts an illustrative embodiment of an electro-acoustic sensor array constituting an essential element of the systems of the present invention, which includes the monitoring of a predetermined area of roadway, called a "predetermined detection zone", for the presence of a motor vehicle and for the classification of such vehicle as a truck within that area. The salient items in Fig. 17 are roadway 1701, automobile 1703, truck 1705, detection zone 1707, microphone array 1711, microphone support 1709, detection circuit 1715 and interface circuit 1719 in a roadside cabinet (not shown), electrical bus 1713, electrical bus 1717 and lead 1721, which conducts a loop relay signal to a command centre.
Each omni-directional microphone in microphone array 1711 receives an acoustic signal which comprises the sound radiated, inter alia, from automobile 1703, truck 1705 and ambient noise. Each microphone in microphone array 1711 then transforms its respective acoustic signal into an analog electric signal and outputs the analog electric signal on a distinct lead on electrical bus 1713 in ordinary fashion. The respective analog electric signals are then fed into detection circuit 1715.
To determine the presence or passage of a motor vehicle in predetermined detection zone 1707, the respective signals from microphone array 1711 are processed in ordinary fashion to provide the sensory spatial discrimination needed to isolate sounds emanating from within predetermined detection zone 1707. The ability to control the spatial directivity of microphone array 111 is called "beam-forming". It will be clear to those skilled in the art that electronically-controlled steerable beams can be used to form multiple detection zones. The analysis of the sounds which emanate from the predetermined detection zone 1707 broadly classifies a vehicle according to its length, the number of axles and the spacing of the axles, i.e., as a truck or not as a truck.
As shown in Fig. 18, microphone array 1711 preferably comprises a plurality of acoustic sensors 1801, 1803, 1805, 1807, 1809, 1811, 1813, 1815 and 1817, (e.
g., omni-directional microphones), arranged in a geometrical arrangement known as a Mill's Cross. For information regarding Mill's Cross arrays, the interested reader is directed to Microwave Scanning Antenna, R.C. Hensen, Ed., Academic Press (1964), and Principals of Underwater Sound (3rd. Ed). R. J. Urick (1983). While microphone array 1711 could comprise only one microphone, the benefits of multiple microphones (to provide signal gain and directivity, whether in a fully or sparsely populated array or vector), will be clear to those skilled in the art. It will also be clear to those skilled in the art how to baffle microphone array 1711 mechanically so as to attenuate sounds coming from other than predetermined detection zone 1707 and to protect microphone array 1711 from the environment (e.g., rain, snow, wind, UV).
Microphone array 1711 is advantageously rigidly mounted on support 1709 so that the predetermined relative spatial positionings of the individual microphones are maintained. The microphone array 1711 may include a set of microphone arrays which are mounted on a mast arm which is supported on a pole, and another set of microphone arrays which are mounted the pole itself. Alternatively, the sets of microphone arrays may be mounted on a highway overpass. The height above the road may be 20 to feet to aim at a point of up to 25 feet. The detection zone typically may cover an area of 4 to 8 feet by 6 to 12 feet. A typical deployment geometry is shown in Fig.
17. In that particular geometry, the horizontal distance of the sensor from the nearest lane with traffic is assumed to be less than 15 feet. The vertical height above the road is advantageously between 20 and 35 feet, depending on performance requirements and available mounting facilities. It will be clear to those skilled in the art that the deployment geometry is flexible and can be modified for specific objectives.
Furthermore, it will also be clear to those skilled in the art how to position and orient microphone array 1711 so that it is well suited to receive sounds from predetermined detection zone 1707.
(vii) DETECTION CIRCUIT
Referring to now to Fig. 19, detection circuit 1715 (See Fig. 17) advantageously comprises bus 1713, (See Fig. 17) bus 1903, vertical summer 1905, analog-to-digital converter 1913, finite-impulse-response (FIR) filter 1917, bus 1903, horizontal summer 1907, analog-to-digital converter 1915, finite-impulse-response (FIR) filter 1919, multiplier 1921 and comparator 1925. The electric signals from microphone 1801, microphone 1803, microphone 1805, microphone 1807 and microphone 1809 (as shown in Fig. 18) are fed, via bus 1901, into vertical summer 1905 which adds them in well-s known fashion and feeds the sum into analog-to-digital converter 1913. While in the illustrative embodiment, vertical summer 1905 performs an unweighed addition of the respective signals, it will be clear to those skilled in the art that vertical summer 1905 can alternatively perform a weighted addition of the respective signals so as to shape and steer the formed beam (ie., to change the position of predetermined detection zone 1707).
It will also be clear to those skilled in the art that illustrative embodiments of an electro-acoustic sensor array providing systems constituting essential elements of the present invention can comprise two or more detection circuits, so that one microphone array can gather the data for two or more detection zones, in each lane or in different lanes.
Analog-to-digital converter 1913 receives the output of vertical summer 1905 and samples it at 32,000 samples per second in well-known fashion. The output of analog-to-digital converter 1913 is fed into finite-impulse response filter 1917.
Finite-impulse response filter 1917 is preferably a bandpass filter with a lower passband edge of 4KHz, an upper passband edge of 6KHz and a stopband rejection level of 60dB below the passband (i.e., stopband levels providing 60dB of rejection). It will be clear to those skilled in the art how to make and use finite-impulse-response filter 317.
The electric signals from microphone 1811, microphone 1813, microphone 1805, microphone 1815 and microphone 1817 (as shown in Fig. 18) are fed, via bus 1903, into horizontal summer 1907 which adds them in well-known fashion and feeds the sum into analog-to-digital converter 1915. While in the illustrative embodiments, horizontal summer 1907 performs an unweighed addition of the respective signals, it will be clear to those skilled in the art that horizontal summer 1907 can alternatively perform a weighted addition of the respective signals so as to shape and steer the formed beam (i.e., to change the position of predetermined detection zone 1707).

Analog-to-digital converter 1915 receives the output of horizontal summer 1905, and samples it at 32,000 samples per second in well-known fashion. The output of analog-to-digital converter 1913 is fed into finite-impulse response filter 1919.
Finite-impulse response filter 1919 is preferably a bandpass filter with a lower passband edge of 4KHz, an upper passband edge of 6KHz and a stopband rejection level of 60dB below the passband (i.e., stopband levels providing 60dB of rejection). It will be clear to those skilled in the art how to make and use finite-impulse-response filter 1919.
Multiplier 1921 receives, as input, the output of finite-impulse-response filter 317 and finite-response-filter 1919 and performs a sample-by-sample multiplication of the respective inputs and then performs a coherent averaging of the respective products. The output of multiplier 1921 is fed into comparator 1925. It will be clear to those skilled in the art how to make and use multiplier 1921.
Comparator 1925 advantageously, on a sample-by-sample basis, compares the magnitude of each sample to a predetermined threshold and creates a binary signal which indicates whether a motor vehicle is within predetermined detection zone 1707.
While the predetermined threshold can be a constant, it will be clear to those skilled in the art that the predetermined threshold can be adaptable to various weather conditions and/or other environmental conditions which can change over time. The output of comparator 1925 is fed into interface circuitry 1719.
Interface circuitry 1719 receives the output of detection circuitry 1715 and preferably creates an output signal such that the output signal is asserted when a motor vehicle is within predetermined detection zone 1707 and such that the output signal is retracted when there is not motor vehicle within the predetermined detection zone 107.
Interface circuitry 1719 also makes any electrical conversions necessary to interface to the circuitry at the command centre of the highway department. Interface circuitry 119 can also perform statistical analysis on the output of detection circuitry 1715 so as to output a signal which has other characteristics than those described above.

(viii) MAXIMALLY-DIGITAL IMPLEMENTATION
Figure 20 illustrates a practical, maximally-digital, implementation. The microphone array 2000 comprises two vertical elements V, and V2, and two horizontal elements H, and H2. As shown, each element has three microphones, which was found 5 practically sufficient. Each of the four elements V~, V2, H, and H2 feeds a respective analog filter 2001 to 2004 to attenuate unwanted noise outside the maximal frequency band of interest, which is normally between 4 and 9 kHz. The filters 2001 to 2004 are each followed by a respective selectable gain pre-amplifier 2005 to 2008, the gain of which is selectable in 3-Db steps ranging from OdB to lSdB (hereinafter to be described 10 more fully later). Four respective analog-to-digital converters 2009 to 2012 follow the pre-amplifiers 2005 to 2008. Respective digital finite impulse response (FIR) filters 2013 to 2016 follow the A/D convertors 2009 to 2012. The FIR filters 2013 to 2016 determine the actual frequency band of operation, which is selected from the following four bands:
15 Band 1 : 4-6 Khz;
Band 2 : 5-7 Khz;
Band 3 : 6-8 Khz; and Band 4 : 7-9 Khz.
20 One value for the gain of all of the pre-amplifiers 2005 to 2008 will normally be selected for the four above bands as follows:
Band 1 Band 2 Band 3 Band 4 9dB lldB l3dB lSdB

6dB 8dB lOdB l2dB

25 3dB SdB 7dB 9dB

OdB 2dB 4dB 6dB

The selection of the frequency band would normally depend on the general nature of the expected vehicle traffic at the particular location of the sensor. The selected gain 30 would depend, in addition, on the distance of the sensor from the road surface. The outputs of the FIR filters 2013 and 2014 (the paths of V, and VZ) are summed in digital summer 2017, while the outputs of FIR filters 2015 and 2016 (the paths of H, and HZ) are summed in digital summers 2017 and 2018. The respective digital summers and 2018 are followed by digital limiters 2019 and 2020, respectively, and the outputs of the latter are input to correlator 2021, the output of which is fed to a parallel-to-serial convertor 2022, the serial output of which would normally be fed to a TDMA
multiplexer (TMDA-MUX) 2023 to be time-division multiplexed with other (conveniently four) processed microphone array signals originating from overhead locations near the array 2000. The multiplexed output of the TMDA-MUX 2023 is then normally relayed by cable 2024 to roadside microprocessor-based controller 2025, where it is demultiplexed in DEMUX 2026 into the original number of serial outputs representing the serial outputs of correlators, e.g., 2021. After demultiplexing in DEMUX
2026, the cross-correlated digital output from the correlator 2021 is integrated in integrator 2027 (which could be a software routine in the microprocessor/controller 2025), and, depending on the correlated/integrated signal level, which is compared to a threshold in vehicle detector 2028, a "vehicle present" signal is issued for the duration above threshold. This information is processed by a flow parameter calculation routine 2029 of the controller 2025, the output of which is an RS232 standard in addition to hard-wired vehicle presence circuits or relays (not shown).
(ix) OPERATION OF CONTROLLER
The operation of the controller 2025, whereby the demultiplexed signal from DEMUX 2026 is processed, will be better explained by reference to the flow-chart shown in Figure 21. The signal is adjusted in gain/offset 2100 depending on user-specific parameters 2101 and then sampled at 2102 and integrated at 2103. The signal sampling 2103 continues until enough samples at 2104 have been collected, upon which the integrator 2103 is reset at 2105 and the mode is determined at 2106. If the mode is initially to indicate vehicle presence, and a vehicle is detected at 2107, which by sound analysis as hereinbefore described, classifies the vehicle as a truck, the decision is immediately outputted at 2107. If the mode 2106 is "free flow", then long term speed average is calculated at 2109 from which variable thresholds are progressively calculated at 2110. That is, the more vehicles there are, the more accurate will the average progressively become. This variable threshold is used to continue to determine vehicle presence at 2111, and to calculate flow parameters 2112. For example, from the average speed and the time the vehicle is in the detection zone, the length of the vehicle is determined, and the truck classification is confirmed. This progressively yields a better determination of the speed of the particular vehicle, given the length of the detection zone. The latter, of course, depends on the frequency band and the distance of the microphone array 2000 from the road surface. On average, in many applications, the length of the detection zone 1707 would be approximately six feet. The flow parameters 2112 are stored in memory 2113 and outputted at 2114 over the RS232 serial link to (other) central traffic management systems (not shown), and where desired activate other interface circuits. As may be seen, the "free flow" processing is iterative in nature, while the binary vehicle presence decision 2106 is determined by a user selected fixed threshold 2108.

Claims

CLAIMS:

1. A traffic monitoring and warning system comprising:
(i) at least one set of sensors comprising a set of electro-acoustic sensors disposed above a traffic lane approaching a hazard for producing signals which are indicative of whether said vehicle is an automobile or a truck and, if it is a truck, to record and specify the configuration of said truck and for providing signals which are indicative of the speed of a truck traversing said second set of sensors;
(ii) a processor having a memory for storing site-specific geometrical and/or dimensional data related both to said hazard and to signals which have been received from said at least one set of sensors; and (iii) a traffic signalling device associated with said traffic lane and which is disposed downstream of said second set of sensors, said traffic signalling device being controlled by said processor;
said processor being responsive to said signals from said at least one set of sensors for computing an actual speed of said truck and for computing a computed maximum speed of said truck;
said computed maximum speed of said truck being derived from said site-specific geometrical and/or dimensional data and from at least said configuration of said truck, said computed maximum speed of said truck being a maximum speed for said truck of said configuration safely to negotiate said hazard;
said processor comparing said computed actual speed of said truck with said computed maximum of safe speed for said truck; and said processor then automatically operating said traffic signalling device if said computed actual speed of said truck exceeds said computed maximum speed for said truck, and also discontinuing operating said traffic signalling device if said computed actual speed of said truck no longer exceeds said computed maximum safe speed for said truck.

2. A traffic monitoring and warning system comprising:
(i) a first set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching a curve for producing signals which are indicative of whether a vehicle is an automobile or a truck, and if it is a truck to specify the configuration of said truck, by providing a set of signals which are indicative of said configuration of said truck;
(ii) a second set of sensors which are disposed in a traffic lane approaching a curve, said set of sensors comprising a set of sensor arrays for providing signals which are indicative of the speed of said truck;
(iii) a third set of sensors for providing signals which are indicative of the height of said truck;
(iv) a processor having a memory for storing site-specific geometrical and/or dimensional data comprising characteristics of said curve and signals which have been received from said sets of sensors; and (v) a traffic signalling device which is associated with said traffic lane and which is disposed downstream of said sets of sensors, said traffic signalling device being controlled by said processor;
said processor being responsive to signals from said sets of sensors for computing an actual speed at which said truck will be travelling on arrival at said curve, and for deriving a computed maximum safe speed for said truck safely to negotiate said curve on the basis of said configuration of said truck as determined by said first set of sensors and on said basis of said height of said truck as determined by said truck height sensor;
said processor comparing said computed actual speed of said truck with said computed maximum safe speed for said truck; and said processor then automatically operating said traffic signalling device if said computed actual speed of said truck exceeds said computed maximum safe speed for said truck, to display a warning to a driver of said truck if said computed actual speed of said truck exceeds said computed maximum safe speed for said truck, and then automatically operating said traffic signalling device if said computed actual speed of said truck exceeds said computed maximum speed for said truck, and also for discontinuing operating said traffic signalling device if said computed actual speed of said truck no longer exceeds said computed maximum safe speed for said truck.

3. A traffic monitoring and vehicle ramp advisory system comprising:
(i) a first set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching a curve for producing signals which are indicative of whether a vehicle is an automobile or a truck, and if it is a truck to specify the configuration of said truck, by providing a set of signals which are indicative of the configuration of said truck, said first set of sensors also for providing signals which are indicative of the speed of said truck;
(iv) a processor having a memory for storing site-specific geometrical and/or dimensional data comprising characteristics of said curve and signals which have been received from said sets of sensors; and (v) a traffic signalling device which is associated with said traffic lane and which is disposed downstream of said set of sensors, said traffic signalling device being controlled by said processor;
said processor being responsive to signals from said set of sensors for computing an actual speed at which said truck will be travelling on arrival at said curve, and for deriving a computed maximum safe speed for said truck safely to negotiate said curve on the basis of said configuration of said truck as determined by said first set of sensors;
said processor comparing said computed actual speed of said truck with said computed maximum safe speed for said truck; and said processor then automatically operating said traffic signalling device if said computed actual speed of said truck exceeds said computed maximum safe speed for said truck, to display a warning to a driver of said truck if said computed actual speed of said truck exceeds said computed maximum safe speed for said truck, and discontinuing operating of said traffic signalling device if said computed actual speed of said truck no longer exceeds said computed maximum safe speed for said truck.

4. The traffic monitoring system as claimed in claim 1, claim 2 or claim 3, wherein a signal for discontinuing operating said traffic signalling device is based on a timer responsive to natural deceleration of the speed of said truck upon the drive of said truck acts on a warning which is provided by said traffic signalling device.

5. The traffic monitoring system as claimed in claim 1, claim 2 or claim 3, wherein a signal for terminating display of said warning which is provided by said traffic signalling device comprises a second set of sensors for providing a set of signals which are indicative of the presence of a truck and the speed of said truck, said second set of sensors being situated upstream of said message sign, and being connected to said processor, said processor being responsive to a signal from said second set of sensors which is indicative of the speed of said truck.

6. The system as claimed in any one or more of claims 1 to 5, inclusive, including a further downstream set of sensors, disposed downstream of said first set of sensors but upstream of said traffic signalling device, said further set of sensors being disposed in said traffic lane approaching said hazard for providing signals which are indicative of the speed of a truck traversing said further set of sensors.

7. The system as claimed in claim 6, further including a still further set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching said hazard for producing signals which are indicative of whether said vehicle is an automobile or a truck and, if it is a truck, to record and specify the configuration of said truck.

8. The traffic monitoring system as claimed in any one or more of claims 1 to 7, inclusive, including a weigh-in-motion scale for supplementing the set of signals which are indicative of said configuration of said truck with signals which are indicative of the actual weight of said truck.

9. A traffic monitoring and traffic light pre-emption system comprising:
(i) a first set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching a traffic-signal controlled intersection for producing signals which are indicative of whether a vehicle is an automobile or a truck, and, if it is a truck, to specify the configuration of said truck, by providing a set of signals which are indicative of said configuration of said truck;
(ii) a second set of sensors comprising a plurality of sensors which are disposed in said traffic upstream of said traffic-signal-controlled intersection having a set of traffic signals and a traffic signal controller, said plurality of sensors comprising a final sensor which is disposed a predetermined distance from said intersection, and a preceding sensor which is disposed a predetermined distance preceding said final sensor in the direction of traffic flow, said preceding sensor providing signals which are indicative of the speed of a truck traversing said set of sensors; and (iii) a processor for storing data including said predetermined distance, said processor being responsive to said signals from said preceding sensor, to said signals from said final sensor, and signals from said electro-acoustic sensors, and to site-specific data, to compute an actual speed of said truck at said final sensor and to compute a maximum speed of said truck, and then to determine whether or not said computed actual speed of said truck exceeds a maximum speed of said truck from which said truck can safely stop at said intersection should said traffic signals require it;
said processor transmitting a pre-emption signal to said traffic signal controller causing said traffic signal controller to switch, or to maintain, said traffic signal to afford right of way through said intersection to said truck in the event that said computed actual speed of said truck exceeds said computed maximum safe speed for said truck.

10. The traffic monitoring and traffic light pre-emption system as claimed in claim 9, wherein said second set of sensors comprises three sets of spaced apart sensors sub-systems.

11. The traffic monitoring and traffic light pre-emption system as claimed in claim 9, wherein said second set of sensors comprises a set of electro-acoustic sensors which are disposed above a traffic lane approaching a traffic-signal controller intersection but downstream of said right set of sensors, for producing signals which are indicative of the speed of said truck.

12. A traffic monitoring and warning system for a blind intersection, said traffic monitoring and warning system comprising:
(i) a first set of sensor comprising a set of electro-acoustic sensors which are disposed above a traffic lane for producing signals which are indicative of whether a vehicle is an automobile or a truck, and, if it is a truck, to specify said configuration of said truck, by providing a set of signals which are indicative of said configuration of said truck;

(ii) a second set of sensors comprising a plurality of sensors which are disposed in a traffic lane upstream of said blind intersection, said plurality of sensors comprising a preceding sensor which is disposed a predetermined distance in advance of said intersection and a final sensor which is disposed downstream from said preceding sensor in the direction of traffic flow, for providing signals which are indicative of the speed of a vehicle; and (iii) a processor having a memory for storing site-specific dimensional data including said predetermined distance, said processor being responsive to the signals from said truck configuration sensor, from said preceding sensor and from said final sensor to compute predicted actual speed of said truck at said final sensor, and for computing a maximum safe speed for said truck and being responsive to signals from said site-specific dimensional data to determine whether or not said predicted speed of said truck exceeds said computed maximum safe speed of said truck at which speed said truck can safely negotiate said blind intersection;
said processor then transmitting a signal to a traffic warning sign to afford right of way through said blind intersection to said truck in the event that said computed actual speed of said truck exceeds said computed maximum speed for said truck.

13. The traffic monitoring and warning system as claimed in claim 12, wherein said second set of sensors comprises a set of electro-acoustic sensors which are disposed above a traffic lane approaching a traffic-signal controller intersection but downstream of said right set of sensors, for producing signals which are indicative of the speed of said truck.

14. A traffic monitoring and traffic signal pre-emption system comprising:
(i) a first set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching a downgrade for producing signals which are indicative of whether a vehicle is an automobile or a truck, and if it is a truck, to indicate said configuration of said truck, for providing a set of signals which are indicative of said configuration of said truck;

(ii) a second set of sensors which are spaced-apart along a traffic lane approaching said downgrade, said second set of sensors providing signals which are indicative of said speed of truck,;
(iii) a processor having a memory for storing site-specific dimensional data related both to said downgrade including the length and severity of said downgrade and to signals from said sets of sensors; and (iv) a traffic signalling device associated with said traffic lane and disposed downstream of said sets of sensors, said traffic signalling device comprising a message sign, said message sign being controlled by said processor;
said processor being responsive to said signals from said sets of sensors for computing a computed actual speed of said truck and for computing a computed maximum safe speed for said truck which is derived from said site-specific dimensional data and from at least said configuration of said truck, said computed maximum speed of said truck being a maximum safe speed for said truck safely to descend said downgrade;
said processor, by comparing said computed actual speed of said truck with said computed maximum safe speed for said truck, only operating said message sign if said computed actual speed of said truck exceeds said computed maximum safe speed for said truck by transmitting a control signal to said message sign, thereby causing said message sign to display said maximum speed for a period of time during which said sign is visible to a driver of said truck.

15. The traffic monitoring and traffic signal pre-emption system as claimed in claim 14, wherein (i) a first set of sensors comprising a set of electro-acoustic sensors which are disposed above a traffic lane approaching a traffic-signal controlled intersection for producing signals which are indicative of whether a vehicle is an automobile or a truck, and, if it is a truck, to specify the configuration of said truck, by providing a set of signals which are indicative of said configuration of said truck;
(ii) a second set of sensors comprising a plurality of sensors which are disposed in said traffic upstream of said traffic-signal-controlled intersection having a set of traffic signals and a traffic signal controller, said plurality of sensors comprising a final sensor which is disposed a predetermined distance from said intersection, and a preceding sensor which is disposed a predetermined distance preceding said final sensor in the direction of traffic flow, said preceding sensor providing signals which are indicative of the speed of a truck traversing said set of sensors; and (iii) a processor for storing data including said predetermined distance, said processor being responsive to said signals from said preceding sensor, to said signals from said final sensor, and signals from said electro-acoustic sensors, and to site-specific data, to compute an actual speed of said truck at said final sensor and to compute a maximum speed of said truck, and then to determine whether or not said computed actual speed of said truck exceeds a maximum speed of said truck from which said truck can safely stop at said intersection should said traffic signals require it;
said processor transmitting a pre-emption signal to said traffic signal controller causing said traffic signal controller to switch, or to maintain, said traffic signal to afford right of way through said intersection to said truck in the event that said computed actual speed of said truck exceeds said computed maximum safe speed for said truck.

16. The traffic monitoring system as claimed in claim 14, wherein a first sub-system of said second set of sensors comprises an above-road electro-acoustic sensors and at least one of presence sensors, axle detectors or height detectors.

17. The traffic monitoring system as claimed in claim 16, wherein said presence sensors are inductive loop or sonic sensors; wherein said axle detectors are piezoelectric, capacitance or fibre optic detectors; and wherein said height detectors are laser, or lightbeam detectors.

18. The traffic monitoring system as claimed in any one or more of claims 1 to 17, inclusive, including a third set of sensors which is disposed between said first set of sensors and said second set of sensors.

19. A traffic monitoring system as claimed in any one or more of claims 9 to 18, inclusive, wherein said preceding sensor comprises first and second sensor arrays which are spaced apart along said traffic lane, said processor being responsive to said data and to signals from said first and second sensors for computing said maximum speed of said truck and being responsive to said signals from said final sensor array for determining said actual speed of said truck at said final sensor.

20. A traffic monitoring system as claimed in any one or more of claims 9 to 19, inclusive, wherein said second set of sensors comprises first, second and third sensor arrays which are spaced apart along a traffic lane upstream of a traffic-signal-controlled intersection having a set of traffic signals and a traffic signal controller;
wherein said second set of sensors each includes sensors for providing signals in dependence upon, at least one physical parameter of said truck which is different from said length of said truck and the number and configuration of axles of said truck;
wherein said processor stores site-specific date including distances between said first and second sensor arrays, and between said third sensor array and said intersection;
and wherein said processor is responsive to said site-specific data and to signals from said second sensor array for computing a maximum safe speed for said truck, and being responsive to signals from said third sensor array for computing actual speed of said truck at said third sensor;
said processor comparing said speed at said third sensor array with said computed maximum safe speed for said truck and, if said speed at said third sensor array exceeds said computed maximum safe speed of said truck, then said processor transmits a signal to said traffic signal controller, thereby causing said traffic signal controller to switch, or to maintain, said traffic signal to afford right of way through said intersection to said truck.

21. A traffic monitoring system as claimed in claim 20, further comprising a camera device which is actuatable is dependence upon a selected signal to capture an image of a truck causing said selected signal.

22. A traffic monitoring system as claimed in claim 21, further comprising a vehicle presence detector downstream of said camera device for generating a signal, when traversed by said truck, for deactivating said camera device.

23. The traffic monitoring system of any one or more of claims 1 to 22, inclusive, wherein said set of electro-acoustic sensors comprises:

(i) a first electro-acoustic sensor for receiving a first acoustic signal which is radiated from said truck at a predetermined zone and for converting said first acoustic signal into a first electric signal that represents said first acoustic signal;
(ii) a second electro-acoustic sensor for receiving a second acoustic signal which is radiated from said truck at said predetermined zone and for converting said second acoustic signal into a second electric signal that represents said second acoustic signal;
(iii) spatial discrimination circuitry for creating a third electric signal which is based on both said first electric signal and on said second electric signal, that substantially represents said acoustic energy emanating from said predetermined zone;
(iv) frequency discrimination circuitry for creating a fourth signal which is based on said third signal; and (v) interface circuitry for creating an output signal which is based on said fourth signal such that said output signal is asserted when said truck is within said predetermined detection zone and whereby said output signal is retracted when said truck is not within said predetermined detection zone.

24. The apparatus of claim 23 wherein said frequency discrimination circuitry comprises a bandpass filter.

25. The apparatus of claim 24 wherein said frequency discrimination circuitry comprises a bandpass filter with a lower passband edge substantially close to 4KH z and an upper passband edge substantially close to 6KHz.

26. The traffic monitoring system of any one or more of claims 1 to 22, inclusive, wherein said acoustic-electric sensors comprise, (a) a plurality of electro-acoustic sensors trained on a predetermined zone, (b) a bandpass filter for processing electrical signals from said plurality of electro-acoustic sensors;
(c) a correlator having at least two inputs and an output for correlating filtered versions of said electrical signals originating from at least two of said plurality of electro-acoustic sensors;

(d) an integrator for integrating said output of said correlator means over time;
and (e) a comparator for indicating detection of said truck when said integrated output exceeds a predetermined threshold.

27. The apparatus as defined in claim 26, further comprising a plurality of analog-to-digital convertors for converting said electrical signals to digital representations prior to said processing thereof.

28. The apparatus as defined in claim 26, wherein said integrator and said comparator are each microprocessor-based programs.

29. The apparatus as defined in claim 26, wherein said plurality of electro-acoustic sensors comprises two vertical and two horizontal multiple-microphone elements, and wherein said correlator means has one of said at least two inputs receiving a sum of said two multiple-microphone vertical elements, and said other of said at least two inputs receiving a sum of said two horizontal multiple-microphone elements.

30. A method of automatically controlling the operation of a traffic signalling device associated with a hazard by analyzing data from any of the systems as claimed in any one or more of claims 1 to 29, inclusive, comprising the steps of:
(i) downloading a set of records of parameters of said specific truck and associated speeds derived from a set of sensors which are disposed upstream of said hazard into a processor;
(ii) downloading a set of records for corresponding parameters of said specific truck and speeds derived from a set of sensors which are disposed downstream of said hazard into said processor;
(iii) matching records, by said processor, of said specific truck from both sets of records;
(iv) computing, by said processor, from said records, an actual speed of said specific truck and a computed maximum safe speed for said truck;
(v) comparing, by said processor, an actual speed of said truck the computer maximises safe speed for said truck;

(vi) automatically operating, by said processor, said traffic signalling device if said computed actual speed of said truck exceeds the computed maximum safe speed of said truck, to display a warning to a driver of said truck when said computed actual speed of said truck exceeds said computed maximum speed of said truck; and (vii) discontinuing, by said processor, opening said traffic signalling device if said computed actual speed of said truck no longer exceeds said computed maximum safe speed for said truck.

31. A method of automatically controlling the operation of a traffic signalling device associated with a curve by analyzing data from any of the systems as claimed in any one or more of claims 1 to 29, comprising the steps of:
(i) downloading a set of records of parameters of said specific truck, including the height of said specific truck, and associated speeds derived from a at least two sets of sensors which are disposed upstream of said hazard into a processor;
(iii) matching records, by said processor, of said specific truck from both sets of records;
(iv) computing, by said processor, from said records, an actual speed of said specific truck and a computed maximum safe threshold speed for said truck from rollover threshold data which has been downloaded from said processor;
(v) calculating, by said processor, an anticipated speed of said truck at the point of curvature of said curve;
(vi) automatically operating, by said processor, said traffic signalling device if said computed actual speed of said truck exceeds the computed maximum safe threshold speed of said truck, to display a warning to a driver of said truck when said computed actual speed of said truck exceeds said computed maximum threshold speed of said truck; and (vii) discontinuing, by said processor, operating said traffic signalling device if said computed actual speed of said truck no longer exceeds said computed maximum safe speed for said truck.

65 37. A method of automatically controlling the operation of a traffic signalling device at an intersection by analyzing data from any of the systems as claimed in any one or more of claims 1 to 22, inclusive, comprising the steps of:
(i) downloading a set of records of parameters of said specific truck and associated speeds derived from at least two sets of sensors which are disposed upstream of said hazard into a processor;
(iii) matching records, by said processor, of said specific truck from both sets of records;
(iv) computing, by said processor, from said records, an actual speed of said specific truck and a computed maximum stopping distance for said truck from stopping threshold data which has been downloaded into said processor;
(v) downloading, into said computer, the actual speed of said truck at a premeasured distance upstream from said traffic signalling device;
(vi) determining, by said processor, whether said truck will be able to stop before said traffic signalling device;
and (vii) from said determination, sending, by said processor, a signal to said traffic signalling device to pre-empt said traffic signalling device.

33. The method as claimed in claim 30, claim 31 or claim 32, including the step of downloading a set of records of the actual weight of the truck.

34. The method as claimed in claim 30, claim 31, claim 32 or claim 33, including the step of addressing a video system to record truck passage at said traffic signalling device.

35. A method for detecting and signalling the presence of a truck in a predetermined zone, and of determining the speed and the configuration of said truck, said method comprising the steps of:
(i) receiving, with a first electro-acoustic sensor, a first acoustic signal which is radiated from a motor vehicle and converting said first acoustic signal into a first electric signal that represents said first acoustic signal;

(ii) receiving, with a second electro-acoustic sensor, a second acoustic signal which is radiated from said motor vehicle and converting said second acoustic signal into a second electric signal that represents said second acoustic signal;
(iii) creating, with spatial discrimination circuitry, a third electric signal, which is based on said sum of said first electric signal and said second electric signal such that said third signal is indicative of said acoustic energy emanating from said detection zone;
(iv) creating, with interface circuitry, a binary loop relay signal which is based on said third electric signal such that said loop relay signal is asserted when said motor vehicle is within said detection zone and such that said loop relay signal is retracted when said motor vehicle truck is not within said detection zone; and (v) comparing said third electric signal to electrical signals from known trucks to determine whether said motor vehicle is a truck, and to compute the speed of said truck, and to compute and specify the configuration of said truck, including length, number of axles, spacing of axles and height.

36. A method for detecting trucks moving through a predetermined zone, and of determining the speed and the configuration of said truck, comprising the steps of:
(i) training a plurality of electro-acoustic sensors on said predetermined zone;
(ii) filtering electrical signals from said plurality electro-acoustic sensors;
(iii) correlating at least two of said filtered electrical signals with one another;
(iv) integrating said results of correlation in said immediately-preceding step over time;
(v) comparing said integrated result of said immediately-preceding step to a predetermined threshold and indicating detection of a motor vehicle when said threshold is exceeded by said integrated result; and (vi) comparing said third electric signal to electrical signals from known trucks to determine whether said motor vehicle is a truck, and to compute the speed of said truck and to compute and specify said configuration of said truck, including length, number of angles, spacing of angles and height.

37. The method as defined in claim 36, further comprising the step of converting said electrical signals to digital representations prior to said filtering.

38. The method as defined in claim 36 or claim 37, wherein the steps of integrating and comparing are each computational routines.

39. The method as defined in claim 36, claim 37 or claim 38 wherein said plurality of electro-acoustic sensors comprises two vertical and two horizontal multiple-microphone elements, and wherein said correlating step continuously correlates the sum of said two vertical multiple-microphone elements with sums of said two horizontal multiple-microphone elements.

40. The system as claimed in any one or more of claims 1 to 22, inclusive, wherein said traffic signalling device comprises a fibre optic sign.

41. A method for providing traffic volume, line occupancy, per vehicle speed and vehicle classification of vehicles travelling along a highway which method comprises:
receiving acoustic signals created and radiated by said vehicles as they travel through a detection zone; and signal processing said acoustic signals; thereby to provide said traffic volume, line occupancy, per vehicle speed and classification of vehicles.

42. The method of claim 41, including the step of using advanced signal and spatial processing to provide adaptive interference cancellation and high resolution multi-lane or multi-zone traffic monitoring, including shoulder activity.

43. The method of claim 41 or claim 42, wherein said acoustic signals are received by means of a non-contact, passive acoustic (listen only) sensor which is mounted on overhead or roadside structures.