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Publication numberUS3613073 A
Publication typeGrant
Publication dateOct 12, 1971
Filing dateMay 14, 1969
Priority dateMay 14, 1969
Publication numberUS 3613073 A, US 3613073A, US-A-3613073, US3613073 A, US3613073A
InventorsClift Eugene Emerson
Original AssigneeClift Eugene Emerson
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Traffic control system
US 3613073 A
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Description  (OCR text may contain errors)

United States Patent FOREIGN PATENTS 436,883 10/1935 Great Britain 340/31 A 985,427 3/1965 Great Britain 340/31 A Primary ExaminerWilliam C. Cooper Att0rneyMason, Fenwick & Lawrence ABSTRACT: A trafi'lc control system for regulating the movement of trafiic at an intersection, including magnetic sensors at the entrance and exit ends of each lane leaving said intersection for producing vehicle count signals for each vehicle entering and leaving the lane, and traffic lights at said intersection having controllers for varying the cycles, offsets and splits thereof for regulating flow of traffic across the intersection into each of said lanes. Counters respond to the count signals for determining the number of vehicles in each selected street block and logic means respond to the counters for determining the direction of the greatest traffic flow and applying control signals to said trafiic signal light controllers to control the same in response to the sensed traffic conditions.

PATENTEDum 12 l97l SHEET 2 OF 3 TRAFFIC CONTROL SYSTEM BACKGROUND AND OBJECTS OF THE INVENTION The present invention relates in general to traffic control systems for automatically regulating vehicular traffic, and more particularly to traffic control systems employing means for sensing the forward flow and density of vehicular traffic along each lane of roadways leaving an intersection and automatically regulating traffic lights in accordance with the actual traffic conditions sensed.

l'leretofore, many efforts have been made to provide devices which will automatically regulate traffic lights at roadway intersections in a manner related to the amount of traffic in the lanes approaching the intersection to provide efiicient flow of traffic. These devices, for the most part, have involved expensive computers and other complex devices as well as expensive wiring installations from a central computer to each vehicle sensor device or equally expensive multiplex hookup costs. 7

The present invention providesa traffic control system employing magnetic sensors placed under the pavement in each lane of trafiic leaving an intersection and connected by a cable to a logic package wherein the number of vehicles entering a given block or section of the roadway is counted, the number of vehicles departing from the same block or section is counted, which results in a running total of vehicles in each control area, and logic means determine the direction of the greatest traffic flow and activates selection means to set the proper timing for offsets, splits and cycles of trafiic lights for etTicient flow of traffic through the intersection.

The present system is completely automatic and all control decisions are made by the logic package installed separately at the various intersections in the highway or roadway system. The electronic logic controls at each intersection are isolated decision-making packages so that failure of traffic lights at any one intersection would not effect the other controls in the system. Also, the use of separate decision-making logic controls at each intersection permits the system to be enlarged or its location changed without the usual problems and costs involved in a centralized system. By the use of magnetic sensing devices placed under the pavement in each lane of traffic leaving the intersection, the operation of the device will not be affected by ice, snow, sludge, or temperature extremes. The system maintains a running total of tralfic volume information from each of the four roadways or blocks immediately ahead of (i.e., in the leaving lanes from) a normal intersection and makes a positive determination of which of the various traffic flows through the intersection is heaviest for appropriate regulation of the traffic lights. Also, on the basis of the stored information as to vehicle density in the blocks immediately beyond the intersection, the system is capable of making a positive decision not to permit additional vehicles to enter this traffic flow when it approaches a saturation level and as long as the saturation level exists, and regulate traffic lights accordingly.

Because the present traffic control system continuously senses and responds to traffic flow volume through its own associated intersection, it is readily able to automatically adjust to the many varied traffic flow changes which occur throughout the day and night to appropriately regulate the traffic lights.

A principle object of the present invention, therefore, is the provision of a novel h'affic control system which includes logic means associated with a particular intersection and sensing means for monitoring vehicular traffic flow through the intersection over a selected block or section of roadway to make traffic flow decisions from such sensed information and automatically operate traffic light signals accordingly, and which system is less complex and expensive than automatic trafiic control systems heretofore provided.

Other objects, advantages, and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment thereof.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a diagrammatic illustration of a roadway intersection and the connecting roadway blocks, showing the location of the vehicle sensors of the present invention;

FIGS. 2A and 2B collectively form a schematic diagram of the logic package providing traffic control at one of the individual intersections;

FIG. 3 is a schematic diagram of an example of the circuit that may be used for the pulse generator PG-l; and

FIG. 4 is a schematic diagram of the circuitry immediately associated with the sensors at the downstream end of the lanes of traffic monitored by sensors MS-l and M84.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawings, wherein like reference characters designate corresponding parts throughout the several figures the automatic traffic control system of the present invention involves an equipment package, hereinafter frequently referred to as a logic package, indicated generally by the reference character 10, associated with a particular roadway intersecti' cin, for example, the intersection 11 illustrated in FIG. 1. The reference character 12 indicates the northbound roadway, 13 the westbound roadway, 14 the southbound roadway, and 15 the eastbound roadway, associated with this intersection 11. Embedded beneath the pavement at the upstream end of each of the traffic lanes leaving this intersection 11 is a magnetic sensor for each respective departing lane, and at the exit or downstream end of each of the corresponding lanes is another similar sensor, each designed to produce a pulse signal of selected duration responsive to passage of a vehicle over the location of that particular sensor. For example, referring to the two northbound trafi'ic lanes of the northbound roadway 12, indicated as left-hand or inner northbound lane 12A and right-hand or outer northbound lane 12B, sensor units MD-J and MD-2 are located at the entrance or upstream ends of lanes 12A and 128, respectively, and sensors MS-3 and MS-4 are located at the exit or downstream ends of these respective lanes. These sensors are commercially available magnetic sensing devices, such as those designated as magnetic field sensors and manufactured by Research Associates, lnc., Linden, N.J., which are buried under the pavement and result in the closure of relay contacts, as indicated schematically in FIGS. 2 and 4, responsive to passage of a vehicle over the sensor to provide an encoding input to the logic package 10, to which the sensors MS-l and MS-Z are connected by cables, and to which the sensors MS-3 and MS-4 are coupled by radio links as later described.

Referrin g, for example, to the sensor MS-l monitoring the entrance end of the lane 12A, it will be noted that its contact is connected through the normally closed contact B of reed relay RE-l to what may be referred to as open contacts BB and A of latching relay LR-l and also to the input Z of pulse generator PG-l designed to scan or oscillate the latching relay LR-l back and forth. Assuming that a vehicle activates the magnetic sensor MS-l resulting in closure of the relay contact indicated at MS-l, power is applied from the closed relay contacts of MS-l through the closed contact 8 of reed relay RE-l to the Contact BB and A of the latch relay LR-l, which will be assumed to be in open condition at this point, and also through the diode D-2 to the input Z of the pulse generator PG-l, a schematic circuit for which is illustrated in FIG. 3. The encoding pulse from the contact of sensing device MS-l which is applied to the input Z of pulse generator PG-l is sent through the closed contact B of the pulse generator and through the resistor R1 to the coil of the reed relay RE-5. The power applied through the closed contact B to the coil of reed relay RE-S instantaneously switches the contact A of relay RE-S to closed condition applying power to the X coil of the latching relay LR-l, closing the contacts BB and A of latching relay LR-l (if they were open) and applying power through the last-mentioned contacts BB and the closed contact B of reed relay RE-4 to the advance terminal CA of counter C-l to advance the counter one count. When the shunted capacitor -C across the coil of relay RE-5 discharges, the relay RE-S drops out and power is switched back to its closed contacts B and BB, the latter applying power to the coil Y of the latching relay SR-l to switch the latter back to the illustrated position wherein contacts B and AA are closed and contact BB and A are open.

It will be noted that it is immaterial which position the latching relay LR-l is in when the pulse generator is activated. For example, assume that the latching relay is in the position established by energization of the Y coil (which may be referred to as the Y coil or open position) wherein the contacts BB and A are closed and the contacts B and AA are open. In this condition, the input pulse from the magnetic MD-l is fed through the BB contact of LR-l, which immediately triggers the count advance circuit of the counter C-l, and is also fed through the A contact of LR-l and the capacitor 1-C to the coil of relay RE-l when the capacitor l-C is charged. This result in transferring the encoding power from the B contact of RE-l to its A contact to hold in the coil of relay RE-l as long as the vehicle which initiated activation of the magnetic sensor MS-l continues activation of that sensor. The blocking diode D-3 prevents a feedback from the A contact of relay RE-l during the hold-in period of the coil. Thetime cycle of the pulse generator P64 is slightly longer than the time required to activate the coil of relay RE-l so that the coil of RE-1 is pulled in and then held in by the closure of its contact A before the pulse generator switches the latch relay LR-l back to the other state. The capacitor lC is provided to insure a make-before-break action of the coil of relay RE-l and the diodes D-1 and 0-2 are provided to block feedbacks from the input point Z of the pulse generator PG-l.

If the latch relay LR-l is assumed to be in the X coil or closed position, wherein the condition of its contacts are as illustrated in FIG. 2, the power supplied by the sensor MS-l through the closed contact B of relay RE-l activates only the pulse generator PG-l, which, after one cycle, will then trigger the Y coil of latch relay LR-l, closing the contacts BB and A and thus resulting in application of an advance pulse to the contact CA of counter C-1 as well as causing energization of the relay RE-l when the capacitor l-C is charged.

It will observed from FIG. 2 that the magnetic sensor MS-Z connects through contact B of reed relay RE-Z with the contacts Band AA of the latch relay LR-1 (which are closed in the X coil position) as well as to the input Z of the pulse generator PG-l. Thus, if the latch relay LR-l is in the X coil position, the pulse from the sensor MS-2 monitoring the lane 128 will be applied through contact AA of the latch relay LR-l to the count advance contact CA of the counter C-l to register another count, and will also be applied through the closed contact B of latch relay LR-l and through the capacitor 2-C to the coil of reed relay RE-Z effecting actuation of this relay in the same manner as relay RE-l was activated responsive to sensor MS-l.

If both sensors MS-l and MS-Z are activated at exactly the same moment, the position of the latching relay LR-l would determine which sensor input pulse would be counted first. Thus, if the latching relay were in the X position, the input pulse from MS-Z would be counted first, while the pulse from sensor MS-l would be counted first if the latching relay were in the Y position. It will be apparent that the input pulses from the sensors MS-l and M84 are terminated as far as the balance of the encoding circuits is concerned by the action of the reed relays RE-l and RE-Z as previously explained. The hold'in action of relays REA and RB2 positively prevents a vehicle from being counted more than once, as might otherwise be the case where traffic is held up momentarily by a traffic signal or for any other reason. For example, if a vehicle is stalled over sensor MS-l, the closure of the contact of MS-l which persists so long as the vehicle remains over the sensor cannot affect other than the first activation of the pulse generator PT-l, due to the opening of the contact B of relay RE-l upon energizing of that relay coil and the holding of that coil in the energized state by its closed contact A for the remainder of the period the vehicle remains over the sensor MS-l. This applies to all sensors used in this invention.

The use of the pulse generator PG-l to switch the latching relay LR-l alternately from the X coil to the Y coil positions permits the counting of vehicles moving in both lanes 12A and 12B regardless if one lane has been stalled. Where more than two lanes of traffic are moving in the same direction, the latching @lay LR-l would be replaced by a ring counter formed fem commercially available hybred reed flip-flops having a single input and parallel output, which in effect would scan the inputs from the plural magnetic sensors monitoring the more-than-two lanes. Of course, additional control relays similar to the relays RE-l and RE-2 would be added for each additional lane in the control system.

The magnetic sensors MS-3 and MS-4 at the exit or downstream ends of the lanes 12A and 12B are provided to count vehicles leaving the block 12 in the respective lanes and subtract the counts from the counter C-l, which is a bidirectional integrated circuit binary counter which drivesits integrated circuit decoder-driver. The encoding circuitry for the magnetic sensors MS3 and M84 is shown schematically in FIG. 4 and incorporates the pulse generator PG-2 which is identical to the pulse generator PG-l for the purpose of scanning or cycling the latching relay LR-Z for the same purpose that the latching relay LR-l is cycled. This block exit or downstream portion of the system is located in a package at the end of the block 12 remote from the intersection 11, and only the pulse signal from each count applied through the contact BB or the contact AA of the latching relay LR-2 is sent back to the base package 10 by any convenient means, such as by cable, or by radio, as indicated schematically in the drawings, and a single cable or radio transmitter-receiver is all that is required in the way of signal connections from the exit end package to the base control package for each counter.

It will be observed from FIG. 2B that count pulses from the sensors MS-l and MS-2 are also applied to the coil of reed relay RE-3 in addition to the circuit through the closed contact B of 'reed relay RE-4 to the count advance contact of counter C-1 and that signals from the encoding sensors MS-3 and MS-4 and their immediately associated circuitry 16 are coupled by radio or by cable, or other convenient means, to the coil of reed relay RE-4 and then in a circuit through the closed contact B of relay RE-3 to the subtract contact CR of counter C-l. The purpose of these two relays RE-3 and RE-4 is to prevent both count advance and count subtract pulses being received at the same time by the counter C-l. It should be apparent that if this occurs, both the coil of RE-3 and RE-4 will be activated, thus blocking both circuits to the counter C-l. Since these two counts cancel each other, the correct setting of the counter C-l is maintained.

Also, it should be mentioned that the speed of the pulse generator PG-l is such that in the event of a slightly staggered relation of encoding pulses reaching the latching relay LR-l, the information (i.e., the pulse signifying detection of a vehicle at the sensor) would beretained until terminated by the appropriate control relay RE-l or RE-Z. The moving vehicle must clear the magnetic sensor before the encoding pulse is terminated, thus creating a lengthy pulse in relation to the high-speed action of the other components of the system. It will be noted that one-shot multivibrators 08-1 and 08-2 are provided in the leads to the count advance and count subtract terminals CA, CR, of the counter C-l these being high-speed, integrated circuits used to insure the proper pulse width to drive the bina y counter (3-1. The counter C-l is preferably an integrated circuit up-down binary counter of conventional construction having an associated integrated circuit decoderdriver DD-l indicated schematically as a series of open contacts.

It will be noted that the contacts of the decoder-driver DD-l associated with the counter C-l are group connected in series of five contacts in each group. Counting from the top, the contact group 1 to S will pull in the coil of reed relay RR-l, the A contact of which connects directly to the 40- second control contact of the traffic signal, for example, the traffic signal 12C in FIG. 1, commanding the northbound traffic flow pattern toward the lanes 12A and 12B in the example shown in FIG. 1. Thus, the counting sensors MS-l and M84 and cooperating sensors MS-3 and MS-4 monitoring the traffic flow in the next block along the lanes 12A and 128 control the counter C-1 and thus the contact condition of the decoder driver DD-l so that if the count during the selected count period in the lanes 12A and 12B totals l to 5, the traffic light 12C will operate on the 40-second cycle (program duration). The next group of five contacts of the decoder driver DD-l will pull the coil of reed relay RR-2, the third group of five contacts pulls in the coil of reed relays RR-3, the fourth group of five contacts activates the coil of reed relay RR-4, and the fifth group of contacts activates the coil of the saturation flow control relay RR-S. The A contact of relay RR-2 connects to the 52-second control contact of the traffic signal 12C, the A contact of RR-3 connects to the 70-second contact of this traffic signal, and the A contact of RR4 connects with the 90- second contact of this traffic signal. The multiple offset command signals (time on green or delay in signal change between successive intersections) are provided by the open relay contacts in FIG. 2A labeled OS-l, 08-2, 08-3 and 08-4. The signal light settings for multiple splits (cycles from green to yellow to red) are provided by the open relay contacts labeled SP4, SP-Z, SP-3 and SP-4. It will be understood that the traffic signals used with this system are of the types now manufactured incorporating switching devices to regulate the cycles, splits and offsets, which require only command signals for proper selections.

It will be appreciated that the number of contacts and groupings in the decoder-driver will depend on the length of the block or the distance to the next signal installation, and whether or not parking is permitted in the block. Any major outlet, such as a parking garage, should be treated the same as an intersection. Driveways and similar outlets should be treated the same as on-street parking and be added before the saturation total level is reached.

The fifth group of contacts of the decoder-driver DD-l controls the saturation flow control relay RR-S, the A contact of which connects to the red light control contact (labeled R) of the signal light installation 12C, commanding the northbound flow of traffic. This "red light will remain on until the subtract sensors MS-3 and MS-4 cause the counter C-l and decoder-driver D-l to step off the block of contacts controlling the relay RR-S, and thus indicate that the saturation level in the relevant block no longer exists. The B contact of the relay RR-S, which is normally closed, is connected to the right-hand green turn arrow control contact of the traffic 13C, so that when relay RR-S is pulled in, it will break the power supply to the right-hand arrow in the westbound lane until the traffic saturation in the northbound lanes of the block 12 clears. The BB contact of relay RR-S connects directly to the left-hand turn arrow control contact (labeled AL) of the traffic signal 15C controlling the eastbound lanes of block 15.

It will be appreciated that counters C-2, C-3 and C-4 and associated decoder drivers DD-2, DD3 and DD-4 are provided for each of the other blocks 13, 14 and 15, each of these counters having similar separate count circuits responsive to magnetic sensors and including pulse generators and latching relays similar to those described in connection with the block 12 and counter C-l.

A time-delay TD1 is provided in association with the saturation flow control relay RR-5 to activate a fail safe" latching relay LR-lA in the event of the failure of the counters C-l to step back off the saturation contact group that controls relay RR-5 after a predetermined time period. Relay LR-lA, when activated, will break the power circuit to the contacts of relay RR-S and provide power through a normally open contact to a yellow flashing circuit, labeled YF in the signal light installation, to continue activating the yellow flashing circuit until the counter C-l corrects itself or the basic control package is repaired or replaced. This action permits traffic flow to continue under caution unless an obvious traffic jam exists.

lnspection of the schematic diagram of FIGS. 2A and 28 will reveal that the counters C-2, C-3 and C-4 and their associated decoder drivers DD-Z, DD-3 and 00-4, having reed relays RR-6 to RR-20, associated with groups of five contacts each control their associated traffic signals in a manner similar to the decoder driver DD-l, and halt traffic flow into the respective blocks they control until the traffic congestion has cleared.

It will be noted that the normally closed B contacts of relays RR-Z, RR-3 and RR-4 are linked in a series hookup involving their counterparts in the decoder drivers driven by the counters C-3, C-2, and C-4. By means of this circuit, the highest block of contacts will control the traffic light control settings and is established by the heaviest traffic tallied by the sensors and counters. In the event the flow is evenly divided, the relays driven by counters 04 would prevail, then C-Zl, followed by C-2 and C-4. The higher decision capacity will go to the counters controlling the major artery at the intersection. It will also be observed that the power out of these closed contacts also controls the common side of the next lower relay in the counter block chain. The saturation flow control relay RR-S, and its counterparts RR-l0, RR-l5 and RR-20, are not involved in this circuit since they halt all traffic flow into a congested block. This permits the system to select the next highest traffic level and permit a continued traffic flow in other available directions. Tracing these circuits involving the B contacts of the relays of the decoder drivers, it will be noted that one branch lead from the B contact of relay RR-4 connects to the coil of relay RR-3 and the other branch lead therefrom connects to the backside of the B contact of relay RR-9. Similarly, one branch lead from the other side of the B contact of relay RR-9 connects to the coil of RR-8 and the other branch lead connects to the backside of the B contact of relay RR-l4. Again, one lead from this contact connects to the coil of RR-l3 and the other lead connects to the backside of the B contact of relay RRl9, one lead from which goes to the coil of RR-l8 and the other lead proceeds to the backside of the B contact of relay RR-3.

It will also be noted from FIGS. 2A and 28 that a timing device TD2 is included in the power supply circuit to the decoder drivers to reset all counter one or more times every 24 hours. This timedelay action will compensate for possible accumulative counting errors that could result from vehicles pulling out of driveways in the opposite direction they entered the block without clearing the subtract sensors, such as sensors MS-3 and MS-4.

Although this description calls for the operation of this system on the basis of the running traffic volume in the im mediate blocks adjacent to the intersection or between the next traffic signals, it should be obvious that the control area could be any distance and other signal lights within the control areas could operate as slaves of the controlled intersection. This would be of particular advantage in areas with few major cross traffic intersections.

I claim:

1. In a traffic control system for regulating the movement of traffic into the leaving lanes of four street sections of selected length leaving in four directions from a roadway intersection, each leaving lane having an entrance end at said intersection and an exit end at the end of said selected length of the street section, a first vehicle detector at the entrance end of each lane leaving said intersection for producing a counter advance signal for each vehicle entering the associated lane, a second vehicle detector at the exit end of each of said lanes for generating a counter subtract signal for each of the vehicles leaving the associated street section for each of said lanes, traffic signal lights at said intersection including traffic light controller means for operating the signal lights in a plurality of different time duration cycles to regulate flow of traffic across said intersection into each of said lanes, plural counting means including a counter for each respective street section for continuously counting the vehicles collectively in all of the leaving lanes of the associated street section responsive to the advance and subtract signals from the detectors for the leaving lanes of the associated street section, each counter having an array or contacts controlled in accordance with the counts for establishing combinations of open and closed contact conditions indicating the collective count of the number of vehicles in the leaving lanes of the associated street section, and logic means responsive to said contact conditions for determining the direction of the greatest traffic flow and applying control signals to said traffic light controller means to control the cycles of said traffic signal lights in selected relation to the sensed traffic conditions.

2. A traffic control system as defined in claim 1, wherein said logic means includes saturation control means coupled to said counting means and responsive to selected contact conditions thereof to determine existence of a vehicle saturation level in any of said street sections and activate said traffic signal lights to halt traffic flow into the lanes of the saturated street section as long as the saturation level persists.

3. A traffic control system as defined in claim 2, wherein said logic means includes route control means to select the next highest count below the saturation level signified by the contact conditions of said counters and control the traffic signal lights in selected relation to said next highest count to permit a continued flow of traffic to unsaturated street sections.

4. A traffic control system as defined in claim 1, wherein said logic means includes means to halt traffic flow into the lanes of a street section having a vehicle saturation level and means for controlling the traffic signal light to maintain traffic fiow into the nonsaturated street sections.

5. A traffic control system as defined in claim 1, wherein said counter for each respective street section includes a counter circuit and said array of contacts controlled thereby is arranged in a numerical series and regulated thereby to produce closure of contacts whose position signifies the number of vehicles in the associated street section, said contacts of such array being grouped in a plurality of serially arranged sets of plural contacts each signifying progressively increasing traffic density levels, and said logic means including a relay coupled to each respective set of contacts to be activated when contacts of its associated set are closed, and the relays associated with said array are coupled to said controller means to respectively establish progressively longer duration traffic signal light cycles for contact closures signifying progressively higher numbers of vehicles.

6. A traffic control system as defined in claim 2, wherein said counter for each respective street section includes a counter circuit and said array of contacts controlled thereby is arranged in a numerical series and regulated thereby to produce closure of contacts whose position signifies the number of vehicles in the associated street section, said contacts of such array being grouped in a plurality of serially arranged sets of plural contacts each signifying progressively increasing trafiic density levels, and said logic means including a relay coupled to each respective set of contacts to be activated when contacts of its associated set are closed, and the relays associated with said array are coupled to said controller means to respectively establish progressively longer duration traffic signal light cycles for contact closures signifying progressively higher numbers of vehicles.

7. A traffic control system as defined in claim 3, wherein said counter for each respective street section includes a counter circuit and said array of contacts controlled thereby is arranged in a numerical series and regulated thereby to produce closure of contacts whose position signifies the number of vehicles in the associated street section, said contacts of such array being grouped in a plurality of serially arranged sets of plural contacts each signifying progressively increasing traffic density levels, and said logic means including a relay coupled to each respective set of contacts to be activated when contacts of its associated set are closed, and the relays associated with said array are coupled to said controller means to respectively establish progressively longer duration trafiic signal light cycles for contact closures signifying progressively higher numbers of vehicles.

8. A traffic control system as defined in claim 4, wherein said counter for each respective street section includes a counter circuit and said array of contacts controlled thereby is arranged in a numerical series and regulated thereby to produce closure of contacts whose position signifies the number of vehicles in the associated street section, said contacts of such array being grouped in a plurality of serially arranged sets of plural contacts each signifying progressively increasing traffic density levels, and said logic means including a relay coupled to each respective set of contacts to be activated when contacts of its associated set are closed, and the relays associated with said array are coupled to said controller means to respectively establish progressively longer duration traffic signal light cycles for contact closures signifying progressively higher numbers of vehicles.

9. A trafiic control system as defined in claim 1, wherein said logic means includes means responsive to different count levels of said counting means to provide different offset and split control signals for application to said controller means which vary in selected relation to the count levels.

10. A traffic control system as defined in claim 2, wherein said logic means includes means responsive to different count levels of said counting means to provide difi'erent offset and split control signals for application to said controller means which vary in selected relation to the count levels.

11. A traffic control system as defined in claim 3, wherein said logic means includes means responsive to different count levels of said counting means to provide different offset and split control signals for application to said controller means which vary in selected relation to the count levels.

12. A traffic control system as defined in claim 5, wherein said logic means includes means responsive to different count levels of said counting means to provide different offset and split control signals for application to said controller means which vary in selected relation to the count level.

13. A traffic control system as defined in claim 5, wherein each of said relays associated with each said array includes relay contact means for establishing offset and split control signals for said controller means which differ for respective sets of said contacts.

14. A traffic control system as defined in claim 6, wherein each of said relays associated with each said array includes relay contact means for establishing offset and split control signals for said controller means which differ for respective sets of said contacts.

15. A traffic control system as defined in claim 7, wherein each of said relays associated with each said array includes relay contact means for establishing offset and split control signals for said controller means which differ for respective sets of said contacts.

16. A traffic control system as defined in claim 1, including timing means to reset said counting means at least once every 24 hours.

17. A traffic control system as defined in claim 1, including relay means activated responsive to selected failure conditions in said logic means to produce signals for activating the associated trafiic signal light in a flashing yellow condition.

18. A traffic control system as defined in claim 1, wherein said logic means includes means for providing control signals for a plurality of different cycles, offsets and splits to apply control signals to said controller means establishing multiple cycles, offsets and splits which differ in selected relation to the count levels of said counting means.

19. A trafiic control system as defined in claim 2, wherein said logic means includes means for providing control signals for a plurality of different cycles, offsets and splits to apply control signals to said controller means establishing multiple cycles, offsets and splits which differ in selected relation to the count levels of said counting means.

ll. said relay contact means for establishing offset and split control signals are associated with said relays in such relation to provide multiple offsets and splits having multiple settings which vary in preselected relation to the traffic density levels signified by said sets of contacts.

Patent Citations
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US5929787 *Nov 27, 1996Jul 27, 1999Mee; Gary L.Vibration actuated traffic light control system
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US6281808Nov 22, 1999Aug 28, 2001Nestor, Inc.Traffic light collision avoidance system
US6573929 *Nov 22, 1999Jun 3, 2003Nestor, Inc.Traffic light violation prediction and recording system
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US7592927 *Dec 2, 2005Sep 22, 2009Robert A MarshallSystem and method for multiplexing traffic signals and bridge collapse detection
US7821422Aug 18, 2004Oct 26, 2010Light Vision Systems, Inc.Traffic light signal system using radar-based target detection and tracking
US8040254Jan 6, 2009Oct 18, 2011International Business Machines CorporationMethod and system for controlling and adjusting traffic light timing patterns
US8725397 *Jun 17, 2010May 13, 2014Toyota Jidosha Kabushiki KaishaTraffic signal cycle estimation device and traffic signal cycle estimation method
WO2000031706A1 *Nov 22, 1999Jun 2, 2000Nestor IncTraffic light collision avoidance system
Classifications
U.S. Classification340/920
International ClassificationG08G1/07, G08G1/08
Cooperative ClassificationG08G1/08
European ClassificationG08G1/08