Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08G—TRAFFIC CONTROL SYSTEMS
  • G08G1/00—Traffic control systems for road vehicles
  • G08G1/01—Detecting movement of traffic to be counted or controlled
  • G08G1/04—Detecting movement of traffic to be counted or controlled using optical or ultrasonic detectors
• • G—PHYSICS
  • G08—SIGNALLING
  • G08G—TRAFFIC CONTROL SYSTEMS
  • G08G1/00—Traffic control systems for road vehicles
  • G08G1/01—Detecting movement of traffic to be counted or controlled
  • G08G1/017—Detecting movement of traffic to be counted or controlled identifying vehicles
  • G08G1/0175—Detecting movement of traffic to be counted or controlled identifying vehicles by photographing vehicles, e.g. when violating traffic rules

Definitions

• the present invention relates to a method for determining the distance between two vehicles running along a section of road or motorway, in particular inside a tunnel.
• the invention relates to an apparatus for determining the distance between two vehicles running along a section of road or motorway, in particular inside a tunnel .
• the highway code obliges vehicles running along roads and motorways to maintain a given safety distance, which varies according to road conditions and in particular according to the maximum allowable speed. Observing the safety distance contributes to improve safety and results in smoother-flowing traffic.
• an object of the present invention is to provide an apparatus for determining the distance between ' two vehicles running along a section of road or motorway which is simple and reliable in operation and is not too costly.
• Figure 1 schematically represents a condition of observance of ' the safety distance between two vehicles running along a section of road or motorway;
• Figure 2 schematically represents a condition of non observance of the safety distance between two vehicles running along a section of road or motorway;
• Figure 3 schematically represents a video camera forming part of the apparatus for determining the distance between two vehicles according to the invention and the associated field of view
• Figure 4 schematically represents a plurality of video cameras forming part of the apparatus for determining the distance between two vehicles according to the invention, where the section of road to be 1 monitored is subdivided into a plurality of subsections;
• Figure 5 schematically represents a subsection subdivided into a plurality of cells
• Figure 6 shows a sequence of images provided by the video cameras of the apparatus according to the invention in the event that the safety distance between two vehicles running along a section of road inside a tunnel is not observed;
• Figure 7 shows the image provided by the number plate recording video camera of the apparatus according to the invention.
• Figure 1 schematically represents a section of road or motorway 10 of length S equal to the prescribed safety distance.
• the references 1 and 2 respectively indicate a first vehicle and a second vehicle running along the road section 10 in the direction indicated' by the arrow A.
• the first vehicle 1 (referred to in the following part of the description as the trailing vehicle) which is about to enter the road section 10 to be monitored is travelling in observance of the prescribed safety distance S only if the road section 10 is free, i.e. if no other vehicle is present at the same time along this section.
• the leading vehicle (referred to in the following part of the description as the leading vehicle) is still within the road section 10, then the distance between the two vehicles, indicated D in Figure 2, is less than the safety distance S.
• the trailing vehicle 1 is therefore in contravention.
• Figure 2 also shows a video camera 3 able to acquire an image of the road section S and to provide as output a video signal, and a processing unit 4 arranged to receive as input at pre-established time intervals the video signal provided by the video camera 3 and to process this video signal through digitization techniques ⁇ so as to detect the possible presence of the leading vehicle 2 in the road section 10.
• the processing unit 4 defines at each processing event the state of the road section 10 as free or occupied, depending on whether the presence of the leading vehicle 2 within the road section 10 has been detected or not at the moment when the trailing vehicle 1 enters the road section 10.
• Figure 3 shows the field of view of the video camera 3, which is installed at a height H from the road surface and is oriented so as to form with its optical axis an angle ⁇ with respect to the horizontal.
• the length of the effective monitoring area of the video camera 3 is indicated T
• the height-limit for the detection of a vehicle by the artificial vision software associated with the video camera 3 is indicated Q.
• the length T is less than the length of the portion of road actually framed by the video camera 3 and depends, In particular, on the height-limit Q.
• the length T is not equal to but is less than the length S of the road section 10 to be monitored, since the safety distance is often such that the road section 10 cannot be monitored using a single video camera 3.
• the road section 10 must therefore be subdivided into a plurality of subsections 12 of length T, each of which is monitored by a respective video camera 3. ⁇
• Figure 4 illustrates how the road section 10 is preferably monitored according to the invention by a plurality of video cameras 3 (in the example illustrated, by four video cameras) linked to the processing unit 4, each of which is intended to monitor a single subsection 12 of length T (in the example illustrated, equal to a quarter of the distance S) . Since the length T of the subsections 12 is less than the length of the portion of road actually framed by a single video camera 3, there is each time an overlapping of the fields of view of two adjacent video cameras.
• the vehicle 1 is not in contravention, i.e. it is observing the prescribed safety distance S, if all the subsections 12 of length T are in the state defined above as free. However, it is . sufficient for any one of the subsections 12 to be in the occupied state, due to the presence of the leading vehicle 2 in this subsection, for the vehicle 1 to be judged in contravention. From a logic point of view, it can therefore be said that the free/occupied state of the monitored road section 10 is given by the OR function of the free/occupied states of all the subsections 12.
• the processing unit 4 is capable of detecting, by processing the video signals from the video cameras 3, the possible presence of the leading vehicle 2 in each of the subsections 12 monitored by the video cameras 3 at the moment of entry of the vehicle 1 into the road section 10 to be monitored. .
• the, detection apparatus is also capable of providing a measurement of the distance kept by the trailing vehicle 1 with respect to the leading vehicle 2 at the moment when the contravention is established.
• the measurement precision of the distance is obviously related to the length of the subsections into which the road section to be monitored is subdivided, i.e. to the number of video cameras 3 used, to improve the measurement precision the number of subsections 12 and therefore the number of video cameras 3 used could be increased. This would involve an increase in costs of the apparatus .
• Each subsection 12 of length T is thus subdivided by the processing unit 4 into a plurality of cells 14 of equal length C, as shown in Figure 5, and the processing unit 4 is capable of determining not only the subsection 12, but also the cell 14 of this subsection in which the leading vehicle 2 is located at the moment when the trailing vehicle 1 enters the road section 10.
• the road section 10 is subdivided into four subsections 12, each of which is in turn subdivided into four cells 14 of length C equal to T/4.
• the distance between the two vehicles 1 and 2 running within the road section 10 can therefore be determined on the basis of the following table:
• the interdistance measurement error can depend on the following factors : length S of the road section 10, number of subsections 12 into which the road section 10 is subdivided, length T of each subsection 12, number of cells 14 into which each subsection 12 is subdivided and length C of each cell 14.
• the interdistance must be measured by always considering the value of the upper limit of the intervals indicated in the above table.
• the measurement error committed by considering the upper limit of the interval is equal to the error committed in the single subsection 12 in which the leading vehicle 2 has been detected. Within each cell 14, the measurements in the interval from 0 to C are approximated to the value C.
• the average measurement error can be calculated as:
• the distance between two vehicles in the road section to be monitored can therefore be estimated with an error that depends only on the number of cells that the image acquiring and processing system (video cameras 3 and processing unit 4) is capable of distinguishing within each subsection.
• a further number plate recording video camera can be provided, not shown in the drawings, intended to acquire in the event of a contravention an image of the number plate of the vehicle 1 that is not observing the prescribed safety ⁇ distance, which image is to be used as documentary evidence for the subsequent notification of the contravention by the traffic police forces .
• the "assessing” event corresponds to the moment when a vehicle enters the road section 10 monitored by the apparatus; this event triggers the execution of the procedure for assessing a possible contravention due to a failure t.o observe the safety distance.
• the "number plate recording” event corresponds to the moment when the vehicle in question reaches the optimal framing position for the number plate recording video camera; this event triggers the acquisition of the image of the number plate of the vehicle in case of a contravention.
• the state of the first cell 14 of the first subsection 12 of the road section is used.
• the passage of a vehicle through the first cell 14 causes the state of this cell to vary in time according to a characteristic square-wave profile: ' the "assessing" event causes the state of the first cell to change from free to occupied, since it corresponds to the instant when the vehicle enters the first cell, while the "number plate recording” event causes the state of the first cell to change from occupied to free, since it corresponds to the instant when the vehicle comes out of the first cell.
• the rising edge of the square-wave profile i.e. the transition from the free state to the occupied state, indicates that the vehicle is entering the first cell.
• the falling edge of the profile i.e. the transition from the occupied state to the free state, indicates that the vehicle is exiting the first cell .
• the time in which the first cell remains in the occupied state depends on the length and speed of the vehicle and on the length C of the first cell .
• the "assessing" and “number plate recording” events described above can be detected either by means of a video camera, advantageously the same video camera 3 intended to acquire the image of the first subsection 12, or by means of field devices (sensors) of different type from the video cameras, such as for example induction coils, laser sensors, photocells, etc.
• the processing unit 4 has fundamentally the function of receiving the video signals from the video cameras 3 and processing these signals in order to identify the conditions of failure to observe the prescribed safety distance, to indicate any contravention, to acquire and make available the necessary documentary evidence for the subsequent notification to the driver of the charged vehicle.
• the processing unit 4 manages at its input the video signals as follows.
• the video signals from the video cameras 3 are processed by an artificial vision software to allow the identification of a vehicle within the road section 10 being monitored.
• the video signal from the first video camera 3 (or from another field device, as specified above) in the driving direction A is used to detect when the "assessing" and "number plate recording” events occur.
• the video signal from the number plate recording video camera is processed in order to acquire the number plate of the vehicle in contravention in order to identify it unambiguously.
• This video camera is positioned in an appropriate manner so as to frame the number plate of the vehicle at the. instant when it is exiting the first cell ("number plate recording" event) .
• the processing algorithm of the processing unit 4 therefore comprises the following steps .
• the processing unit 4 starts to scan the images from the video cameras 3 in order to identify any leading vehicles 2 within the road section 10. If the vehicle 2 is detected within the road section 10, i.e. in presence of a violation due to a failure to observe the safety distance, the processing unit 4 activates the number plate recording video camera to acquire an image of the number plate of ⁇ the vehicle 1 in contravention.
• the processing unit 4 measures the distance of the trailing vehicle 1 from the leading vehicle 2 and stores the images acquired by the video cameras 3 at the moment of entry of the vehicle 1 into the road section 10.
• the processing unit 4 acquires by means of the number plate recording video camera the image of the number plate of the vehicle in contravention. All the images stored by the processing unit are accompanied by an indication of the instant of acquisition, so as to provide complete and indisputable documentation of the contravention committed.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Traffic Control Systems (AREA)
• Length Measuring Devices With Unspecified Measuring Means (AREA)

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• 2006
  • 2006-11-15 AT AT06832321T patent/ATE483220T1/de active
  • 2006-11-15 DE DE602006017276T patent/DE602006017276D1/de active Active
  • 2006-11-15 EP EP06832321A patent/EP2084689B1/fr active Active
  • 2006-11-15 WO PCT/IT2006/000796 patent/WO2008059538A1/fr active Application Filing
• 2010
  • 2010-02-04 HK HK10101251.0A patent/HK1137561A1/xx not_active IP Right Cessation

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