US3883842A

US3883842A - Traffic staging control system

Info

Publication number: US3883842A
Application number: US364436A
Authority: US
Inventors: Anthony B Marmo
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-05-29
Filing date: 1973-05-29
Publication date: 1975-05-13
Anticipated expiration: 1992-05-13

Abstract

This is a system for regulating traffic flow by limiting the number of vehicles that can pass a given point on the roadway in a given interval of time. Basically, it provides a staging area in the roadway having a plurality of staging zones wherein each zone is provided with a traffic control means, such as a signal light or gate. Irrespective of the number of zones in the staging area, and of the size of the staging zones, the traffic in each zone is released successively as the traffic in the zone ahead has cleared its zone. Then, when the entire staging area is clear of traffic, the cycle of events is repeated, first stopping the traffic in the first zone and permitting traffic to accumulate therebehind, then again releasing the first zone of traffic, then again releasing each zone successively. The timing of these events determines the maximum rate of regulated flow of traffic. When traffic flows into the staging area at a rate less than this maximum, the number of vehicles accumulating in each zone will be less than the capacity of the zone. When traffic demand exceeds the maximum rate of regulated flow, all zones will be filled to capacity, a waiting line will develop behind the staging area, and traffic will leave the staging area at the regulated flow rate. Since this rate is always set at a value below the capacity of the roadway, congestion and attendant deterioration of conditions on the roadway during ''''rush-hour'''' periods are thereby eliminated. When the staging control is applied to a multilane roadway, events in the staging cycle may be caused to occur at different times in each lane to smooth out traffic flow or for other reasons. Traffic is not permitted to change lanes in the staging areas. It is also particularly useful in merging a greater number of lanes to a lesser number, both on the highway and at bridge or tunnel approaches. It may also be used for assigning a higher priority to a bus or car pool lane over the other lanes of the roadway by delaying the signals of such other lanes. It may also be used as a ramp metering system, with a greater number of zones in the area and with the zones of lesser length, as for even one or two cars. A basic feature of the traffic staging control system is that each car entering the staging area, irrespective of which zone it may be stopped in, makes only one stop in the staging area, and then when released moves on through all other forward staging zones without stopping and thus onto the highway.

Description

[ May 13, 1975 Marmo TRAFFIC STAGING CONTROL SYSTEM [76] Inventor: Anthony B. Marmo, 7916 Coral Blvd., Miramar, Fla. 33023 [22] Filed: May 29, 1973 [2]] Appl. No.: 364,436

[52] US. Cl 340/41 R [51] Int. Cl G08g 1/085 [58] Field of Search 340/31 R, 35, 36, 40, 41 R [56] References Cited UNITED STATES PATENTS 3,241,107 3/1966 Duvivier 340/36 3,302,168 l/l967 Gray et al. 340/31 R 3,304,539 2/1967 Auer, Jr. 340/36 3,384,869 5/1968 Waldron 340/36 3,508,191 4/1970 Barker et al. 340/31 R 3,518,622 6/1970 Barker et al. 340/31 R 3,529,284 9/1970 Villemain 340/35 3,593,262 7/1971 Spencer 340/36 3,783,446 l/l974 McGimpsey 340/31 R Primary Examiner-Kathleen H. Claffy Assistant Examiner-RandallP. Myers Attorney, Agent, or FirmGustave Miller 57 ABSTRACT This is a system for regulating traffic flow by limiting the number of vehicles that can pass a given point on the roadway in a given interval of time. Basically, it provides a staging area in the roadway having a plurality of staging zones wherein each zone is provided with a traffic control means, such as a signal light or gate. Irrespective of the number of zones in the staging area, and of the size of the staging zones, the traffic in each zone is released successively as the traffic in the zone ahead has cleared its zone. Then, when the entire staging area is clear of traffic, the cycle of events is repeated, first stopping the traffic in the first zone and permitting traffic to accumulate therebehind, then again releasing the first zone of traffic, then again releasing each zone successively.

The timing of these events determines the maximum rate of regulated flow of traffic. When traffic flows into the staging area at a rate less than this maximum, the number of vehicles accumulating in each zone will be less than the capacity of the zone. When traffic demand exceeds the maximum rate of regulated flow, all zones will be filled to capacity, a waiting line will develop behind the staging area, and traffic will leave the staging area at the regulated flow rate. Since this rate is always set at a value below the capacity of the roadway, congestion and attendant deterioration of conditions on the roadway during rush-hour periods are thereby eliminated.

When the staging control is applied to a multilane roadway, events in the staging cycle may be caused to occur at different times in each lane to smooth out traffic flow or for other reasons. Traffic is not permitted to change lanes in the staging areas. It is also particularly useful in merging a greater number of lanes to a lesser number, both on the highway and at bridge or tunnel approaches. It may also be used for assigning a higher priority to a bus or car pool lane over the other lanes of the roadway by delaying the signals of such other lanes.

It may also be used as a ramp metering system, with a greater number of zones in the area and with the zones of lesser length, as for even one or two cars.

A basic feature of the traffic staging control system is.

that each car entering the staging area, irrespective of which zone it may be stopped in, makes only one stop in the staging area, and then when released moves on through all other forward staging zones without stopping and thus onto the highway.

4 Claims, 2 Drawing Figures SEWENCE TABLE l f I /8 20 EVENT TIME START SIGNAL CONDITION NUMBER NUMBER INTERVAL TIME RESULTS OF CARS seconds) D C B A RELEASED 1 +5 G G G R Cars collect in O staging zone AB 2 20 G G R G Cars leave zone AB,

' collect in zone BC 3 G R G G Cars leave zone BC, 15

collect in zone CD 30 R G G G Cars leave zone CD, 15

collect behind D 5 +5 G Same as event 1 6 20 G G G Same as event 2 15 and so on MENIEBHM 1 3197s 3883.842

TRAFFIC STAGING common D C B A 0 O Q 0 Traffic 0 G O O Signals Staging Zone CD 4 Zone BC 4 Zone AB Zones Direction of Traffic Flow ,4 SEQUENCE TABLE 4 /a 24 Z EVENT TIME START SIGNAL CONDITION NUMBER NUMBER INTERVAL TIME RESULTS OF CARS (seconds) D C B A RELEASED 1 +5 0 G G G R Cars collect in O staging zone AB 2 +5 G G R G Cars leave zone AB, 15

1 collect in zone BC 3 G R G G Cars leave zone BC, 15

collect in zone CD 30 R G G G Cars leave zone CD, 15

collect behind D 5 +5 I G G G R Same as event 1 0 6 20 G G R G Same as event 2v 15 and so on TRAFFIC STAGING CONTROL SYSTEM BACKGROUND OF THE INVENTION All highways have a limited capacity, that is, they can accommodate a maximum number of vehicles per mile at some Optimum speed, and when more than that number of vehicles is allowed on the highway, it becomes congested and traffic slows down or even stops for indeterminate intervals. It is axiomatic that rush-hour traffic is congested and slow because the normal capacity of the highway is being exceeded. This makes it desirable to regulate the rate of flow of vehicles entering a section of highway. For example, traffic signals have been installed on freeway entrance ramps in several cities to limit the number of vehicles entering the freeway when it becomes congested. This is called ramp meter ing, and in its simplest form consists of a traffic signal and a controller which alternates the green and red lights to allow one car at a time to enter the freeway. The maximum metering rate with such a control is 720 vehicles per hour. This is discussed on Page 140 of Design of Freeway Entrance Ramp and Merging Control Systems, by Buhr, McCasland, Carvell and Drew, pgs. 137-149, Highway Research Record No. 279, Highway Research Board, Washington, DC. 1969.

Often a higher rate of regulated flow is needed. At the first downtown entrance to an urban freeway, or on an entrance ramp at an interchange where the freeway widens from two to three lanes, the desired flow may be in excess of 1500 vehicles per hour. This cannot be achieved by metering one vehicle at a time (720 vph maximum). It has been suggested that two or three vehicles be allowed to pass on each green signal to increase the rate of flow (see Page 141 of above identified publication). The major objection to this form of regulation (one, two or three vehicles at a time) is that it requires all waiting vehicles to start and stop each time the lead vehicle enters the freeway. This condition becomes more serious during peak traffic periods when longer waiting lines develop.

OBJECTS OF THE INVENTION This invention relates to a traffic staging control system that limits the number of vehicles passing a given point on the roadway in a given time interval.

This invention has for an object to regulate the traffic on or entering a highway in such a manner that a maximum desired rate of flow will not be exceeded.

It is a further object of this invention to achieve such control with minimum inconvenience to vehicle operators.

It is a further object of this invention to provide a traffic staging area consisting of a plurality of staging zones for a lane of traffic so that the traffic in that lane will be limited to a desired maximum rate of flow.

A further object of this invention is to provide a series of traffic staging zones with a traffic control means at the head end of each zone, as well as at the tail end of the last zone, and to operate the traffic control means so the traffic in each staging zone is released after the traffic in the zone ahead has cleared that zone.

Yet a further object of this invention is to provide a succession of traffic staging zones, each capable of holding a desired number of cars, in one embodiment, approximately fifteen average size cars, and then releasing the cars in each zone successively after the cars in the zone ahead have cleared the staging area.

A further object of this invention is to provide a traffic control system wherein each car, after entering the staging area, is stopped only once before it is permitted to continue on or enter the highway, irrespective of the number of staging zones there are in the staging area.

A further object of this invention is to provide a means for safely merging traffic from a greater to a lesser number of lanes.

A further object of this invention is to provide a means for assigning different priorities to each lane of traffic.

A further object of this invention is to provide an improved traffic control system that is an improvement over that shown in Patents issued, as follows: Waldron, U.S. Pat. No. 3,384,869; Barker et a1, U.S. Pat. No. 3,518,622; Villemain, U.S. Pat. No. 3,529,284; Spencer, U.S. Pat. No. 3,593,262; Barker et a1, U.S. Pat. No. 3,508,191.

DESCRIPTION OF THE FIGURES With the foregoing and other objects in view, as will hereinafter become apparent from the following detailed description, when read in conjunction with the accompanying drawing, wherein:

FIG. 1 is a schematic illustration of the staging area of this invention.

FIG. 2 is a sequence table showing the timing of the traffic signals and the movement of vehicles in and out of the staging area during a complete cycle of events.

DETAILED DESCRIPTION OF THE INVENTION This is a system for regulating traffic flow by limiting the number of vehicles that can pass a given point on the roadway in a given interval of time. It provides a staging area 10 in which all traffic is controlled by being stopped in one of the various staging zones AB, BC or CD of the staging area 10. In this illustration of this invention, three staging zones AB, BC and CD are provided in the staging area 10, each zone being intended to hold about fifteen cars of average size, in which case, each zone is about three hundred feet in length, and wide enough to hold the maximum car, truck or bus width. Each staging zone has a traffic signal or control having its conventional timing means, such as a light, A, B and C at its head end, and staging area 10 also has a traffic signal D at its entrance. Only one traffic signal or control is stop or red at one time, while all the other signals are go or green at the same time.

As shown in the sequence table of FIG. 2, signal A is red in event 1, while signals B, C and D are green, permitting cars to collect in staging zone AB up to the limit of its capacity, and then cars may collect in successive zones BC and CD, and then behind signal D, depending on the traffic on the highway therebehind. During event 1, that is, the filling of Zone AB, a time interval of 45 seconds is permitted, this being more than the time it takes cars, of average acceleration and braking ability, to pass through the entire staging area 10 into staging zone AB. Then, signal A turns green, while signal B turns red, thus commencing event 2, and the cars traffic in zone CD and therebehind, and signal B turns green, permitting the cars in zone BC to leave onto the highway, traveling through zone AB on their way. Then twenty-five seconds later, event 4 commences, signal C turns green, and signal D turns red, for an interval of 5 thirty-seconds, permitting all the cars in zone CD to leave and go on the highway. Next, event 5 commences, signal D turns green, while signal A turns red, and the entire cycle is repeated, as also illustrated in the sequence table of FIG. 2.

In this sequence table, the above events are illustrated graphically, the first column 12 showing the sequence of events, the second column 14 showing the time interval that each particular event occupies, the third column 16 showing the starting time in seconds for each event from the beginning. The fourth column 18 shows the simultaneous signal conditions for each event. The fifth column 20 shows the results of the signal conditions of each particular event, while the sixth column 22 shows the number of cars released onto the highway during each event, assuming fifteen cars capacity for each zone. The rate of flow is 45 vehicles in each two-minute interval or 1350 vehicles per hour. This is a maximum rate of flow which results when traffic entering the staging area equals or exceeds 1350 vehicles per hour. During periods of light traffic, the flow leaving the staging area will equal the flow entering the area, and each zone will accumulate less than fifteen cars for release to the roadway.

As is obvious from the above description and the sequence table, each car is stopped once, and only once, while in the staging area 10, and thereafter each car travels freely without being stopped at all, unless other cars enter the roadway at a point or points beyond the staging area and in numbers sufficient to exceed the capacity of the roadway.

The number of staging zones is optional. Fewer zones would reduce the cost of the installation but increase the total number of vehicle stops and starts. Notice that most vehicles in zone AB must stop twice before they are released to the highway, once behind signal D and once behind signal A. Vehicles in zones BC and CD stop only once. Thus, with four traffic signals, 67 percent of the vehicles are stopped only once. Adding a fifth signal and a fourth staging zone will increase this to 75 percent. With six signals and five staging zones 80 percent of the vehicles are stopped only one time. These percentages are correct as long as traffic entering the staging area is less than or equal to the regulated flow rate. With higher input (or lower regulated flow) a waiting line will develop, and vehicles in that line may be stopped once or twice before they reach a staging zone.

The time intervals and/or the number of events may be set up differently from that above, depending on the rate of flow desired and the characteristics of the roadway and the vehicles.

When there are several lanes, the events of the staging zones in one lane may be out of phase with the events of the corresponding staging zones of the other lanes, so that the cars will leave onto the highway from one lane while the cars in another lane may be stopped, or starting to leave at a different interval, thus smoothing out the traffic flow on the highway beyond the staging areas.

At a bridge or tunnel approach, staging areas serve for merging traffic from adjacent zones by phasing the For example, if ten signals are installed with only one car length between each of them, during event 1 (first signal red, all others green) ten cars will move into the staging area. During event 2 (second signal red, all others green), the first car will be released; during event 3 the second car will be released, and so on. If event 1 takes 40 seconds, and events 2 through 10 take 5 seconds each, total elapsed time for a complete staging cycle is seconds. During that time, nine cars have been released for a flow rate of about 380 vehicles per hour.

When events 2 through 10 have the same time intervals, the rate of flow is fixed and determined by that time interval. In the example above, a time interval of 10 seconds would reduce flow to about 250 vph.

On some freeways, traffic control computers regulate the entrance ramp flow in response to conditions on the freeway. The flow rate from the entrance ramp is variable, each car on the ramp being released when the computer determines that there will be room for it on the freeway (see Waldron U.S. Pat. No. 3,384,869; Barker U.S. Pat. No. 3,518,622 and Barker U.S. Pat. No. 3,508,191). It is obvious that this computer can also release each staging zone, in succession, to achieve the same variable flow.

Staging controls should be used on all high-volume freeway entrance ramps instead of conventional ramp metering devices. Staging controls may also be installed on exit ramps (and on all lanes at the end of a freeway) to store peak-hour traffic and then discharge it at a rate that surface roads can handle.

Full control of a freeway can be achieved with staging controls installed on all freeway lanes (at one or more critical locations) and metering devices or staging controls on selected entrance and exit ramps. On some freeways, it may be desirable to control each lane at a different rate of flow. Less traffic in the curb lane can improve merging from entrance ramps, and the inside lane can generally accommodate a higher rate of flow. Such lane-to-lane variations in regulated flow can be achieved with all traffic signals operating in the same time sequence (if the length of staging zones is different for each lane) or with the same length staging zones (if the signal timing is varied for each lane). No lane changing is permitted in the staging area. Staging controls can also be set to give higher priority to one or more lanes, such as for buses or car pools, to allow these vehicles more rapid access to a freeway, tunnel or bridge than the rest of the traffic.

The Traffic Staging Control can also provide safe and efficient merging when one or more lanes on a highway are terminated. This is especially important during peak traffic periods when, for example, three congested lanes cannot safely be merged into two. The staging control, however, can stop all traffic on the three congested lanes, and then release it at a rate that does not exceed the capacity of the two available lanes.

Among the advantages of the Traffic Staging Control System is that it provides a steady regulated flow of traffic, even at high flow rates. It minimizes stop-and-go driving for vehicles in the waiting line. It can be constructed from standard traffic signal and control components. It can be used as a merge control for highway or city traffic.

ABSTRACT OF DRAWING In the drawing, like reference numerals in the two figures refer to like parts for the purposes of explication, and marshalled below are the reference numerals of this improved Traffic Staging Control System:

traffic staging area l2 column of events 14 column of time intervals in area 16 starting time column 18 signal conditions column 20 results column 22 column of cars released A traffic signal at end of zone AB AB zone between A and B B traffic signal at end of zone BC BC zone between B and C C signal at end of zone CD CD zone between BC and D D signal at entrance of staging area 10 consisting of a plurality of' successive contiguous staging zones of predetermined average vehicle capacity, a plurality of spaced uni-directional stop and go traffic signals on said staging area, the size of each staging zone being determined by the spacing of the traffic signals, one signal being at the entrance to said staging area and one signal being at the exit end of each staging zone, said traffic signals being coordinated to provide a stop indication at only one signal at a time while simultaneou sly providing a go indication at each other signal, the stop indication progressing successively from the foremost signal at prescribed intervals to the next rearward signal, and then, at a prescribed time interval, the cycle is repeated indefinitely.

2. The uni-directional traffic control system of claim 1, there being a separate staging area for each traffic lane of a multiple lane highway, the traffic indications of each lane being coordinated in staggared relation to each other lane, wherey the traffic release in each lane is out of phase with the traffic release of each of the other lanes.

3. The uni-directional traffic control system of claim 2, said traffic indications being coordinated to alternate the release of traffic from a greater number of lanes to a lesser number of lanes to thereby safely merge the traffic from a greater number of lanes into a lesser number of lanes.

4. The uni-directional traffic control system of claim 1, there being a separate staging area for each traffic lane of a multiple lane highway, the traffic indications of each lane being coordinated to provide priority in one or more lanes of the highway and to release traffic in the non-priority lanes at a lower rate than in the one or more priority lanes.

Claims

1. A uni-directional traffic control system for limiting the flow of traffic on a uni-directional highway to a desired maximum rate of flow comprising a staging area consisting of a plurality of successive contiguous staging zones of predetermined average vehicle capacity, a plurality of spaced uni-directional stop and go traffic signals on said staging area, the size of each staging zone being determined by the spacing of the traffic signals, one signal being at the entrance to said staging area and one signal being at the exit end of each staging zone, said traffic signals being coordinated to provide a stop indication at only one signal at a time while simultaneously providing a go indication at each other signal, the stop indication progressing successively from the foremost signal at prescribed intervals to the next rearward signal, and then, at a prescribed time interval, the cycle is repeated indefinitely.

3. The uni-directional traffic control system of claim 2, said traffic indications being coordinated to alternate the release of traffic from a greater number of lanes to a lesser number of lanes to thereby safely merge the traffic from a greater number of lanes into a lesser number of lanes. 4. The uni-directional traffic control system of claim 1, there being a separate staging area for each traffic lane of a multiple lane highway, the traffic indications of each lane being coordinated to provide priority in one or more lanes of the highway and to release traffic in the non-priority lanes at a lower rate than in the one or more priority lanes.