Responsive traffic light control system and method based on conservation of aggregate momentum
First Claim
1. A traffic control system for controlling vehicular traffic flow at an intersection of roadways with the objective of increasing the average vehicular velocity and reducing the average number of stops without compromising safety or introducing intolerably long delays for adversely affected vehicles comprising:
- a multiplicity of sensors positioned for sensing aggregate vehicular momentum and congestion experienced for each of the vehicles passing through a predetermined zone on each such roadway upstream from the intersection,processor means connected to the respective sensors for generating first and second sequences of pulses for each vehicle passing the sensed zone, in which each first sequence is representative of each vehicle'"'"'s momentum, or preferably, its velocity times its incremental length, and each said second sequence is representative of the congestion experienced by each sensed vehicle,first summing means connected to said processor means for generating a first running sum of the pulses in the successive first sequences, said first running sum being representative of aggregate momentum of the sensed vehicles on the respective roadway, and for generating a second running sum of the pulses in the successive second sequences, said second running sum being representative of the aggregate congestion experiences by the sensed vehicles on the respective roadway,further summing means connected to said first summing means and to said second summing means for generating a third running sum of said first and second running sums for a roadway having a "go" signal and for providing only the first running sum for a roadway having a "stop" signal,means for sensing whether the traffic control light facing a respective roadway is "go" or "stop",forecasting means under control of said go/stop sensing means, and connected to said processor means for forecasting when the sensed vehicles on a respective roadway will likely pass through the intersection and for forecasting when the sensed vehicles on the respective roadway will likely become stopped at the intersection, said forecasting means being connected with said further summing means for subtracting from said third running sum respective portions of said first and second running sums representative of the contribution to aggregate momentum and aggregate congestion of the respective forecasted vehicles for producing a corrected third running sum for each roadway,comparison means for comparing the respective corrected third running sum for each roadway, andlight timer means connected and under the control of to said comparison means for lengthening the "go" signal relative to the "stop" signal for the respective roadway having the greater corrected third running sum applicable thereto and for speeding up said timer means if the signal is on "stop" or slowing or stopping said timer means if the signal is on "go".
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Abstract
A system to improve traffic flow on all types of interconnected roadways, which reduces fuel consumption, emissions and trip times, is based on adaptive control of traffic signal timing. The parameters used to exercise this control are generated by sensing presence, duration, time, and velocity of vehicles passing a narrow road segment upstream from the signallized intersection and with intersections in proximity to each other, also downstream from that intersection. The information generated by each sensor is processed into three running aggregate quantities; aggregate momentum data, aggregate experienced congestion data and aggregate stopped vehicles data. A fourth quantity, triggered by tentative platoon identification, is based on velocity and density of a small sample of vehicles and speeds response time to an approaching platoon by pre-empting signal timing briefly. For intersections embedded in arterials and networks of roads, a fifth quantity is introduced by a pre-programmed clock, which acts to synchronize the timing offsets between adjacent intersections, to expedite traffic flow given the average traffic condition and other apriori information. The aggregate quantities are summed together in combinations determined by the traffic signal condition. The sums are compared with equivalent sums generated by processors associated with the intersecting roadway, generating a difference magnitude which in turn controls an adjustable rate clock, depending on existing signal conditions. A modification of this method for intersections of three or more roadways or for intersections including phased left-turn lanes is described.
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Citations
28 Claims
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1. A traffic control system for controlling vehicular traffic flow at an intersection of roadways with the objective of increasing the average vehicular velocity and reducing the average number of stops without compromising safety or introducing intolerably long delays for adversely affected vehicles comprising:
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a multiplicity of sensors positioned for sensing aggregate vehicular momentum and congestion experienced for each of the vehicles passing through a predetermined zone on each such roadway upstream from the intersection, processor means connected to the respective sensors for generating first and second sequences of pulses for each vehicle passing the sensed zone, in which each first sequence is representative of each vehicle'"'"'s momentum, or preferably, its velocity times its incremental length, and each said second sequence is representative of the congestion experienced by each sensed vehicle, first summing means connected to said processor means for generating a first running sum of the pulses in the successive first sequences, said first running sum being representative of aggregate momentum of the sensed vehicles on the respective roadway, and for generating a second running sum of the pulses in the successive second sequences, said second running sum being representative of the aggregate congestion experiences by the sensed vehicles on the respective roadway, further summing means connected to said first summing means and to said second summing means for generating a third running sum of said first and second running sums for a roadway having a "go" signal and for providing only the first running sum for a roadway having a "stop" signal, means for sensing whether the traffic control light facing a respective roadway is "go" or "stop", forecasting means under control of said go/stop sensing means, and connected to said processor means for forecasting when the sensed vehicles on a respective roadway will likely pass through the intersection and for forecasting when the sensed vehicles on the respective roadway will likely become stopped at the intersection, said forecasting means being connected with said further summing means for subtracting from said third running sum respective portions of said first and second running sums representative of the contribution to aggregate momentum and aggregate congestion of the respective forecasted vehicles for producing a corrected third running sum for each roadway, comparison means for comparing the respective corrected third running sum for each roadway, and light timer means connected and under the control of to said comparison means for lengthening the "go" signal relative to the "stop" signal for the respective roadway having the greater corrected third running sum applicable thereto and for speeding up said timer means if the signal is on "stop" or slowing or stopping said timer means if the signal is on "go". - View Dependent Claims (2, 3, 4)
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5. A traffic control system that takes into account energy consumption and emissions of moving and stopped vehicles comprising:
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a velocity indicating sensor and a presence sensor that monitor a specified narrow segment of roadway for producing velocity data and presence time data for each vehicle passing said segment of roadway, multiplication means connected to said sensors which multiplies the velocity data by the presence time data resulting in a vehicle length indication for each such vehicle, first processing means connected to said multiplication means for generating aggregate momentum data which is comprised of the running sums of velocity data times said length indication for each such vehicle between the segment of roadway and an intersection, second processing means connected to said multiplication means for generating aggregate congestion data which is comprised of running sums indicative of inverse velocity data for each vehicle times each vehicle'"'"'s length indication for each such vehicle present between the segment of roadway and the intersection, third processing means connected to said multiplication means for generating aggregate stopped vehicles data which is comprised of the running sum of vehicle length indications for each vehicle which has passed said segment of roadway and is waiting at a stop signal, and means for controlling traffic connected to said first, second and third processing means for controlling the traffic as a function of said aggregate momentum data, said inverse velocity data and said aggregate stopped vehicles data for minimizing energy consumption and emissions of moving and stopped vehicles. - View Dependent Claims (6, 7)
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8. A traffic control system for controlling vehicular traffic at the intersection of more than two multiple roadways or at an intersection with phased left turn intervals is comprised of;
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a multiplicity of sensors located upstream from the intersection on each intersecting roadway or left turn lane, a multiplicity of processors for converting the sensed data into aggregate momentum, aggregate congestion and aggregate stopped vehicle parameters, a first summing means for adding said parameters together for the roadway or lane with a "go" signal condition, a second summing means for adding stopped vehicle parameters for the roadways and lanes with a "stop" signal condition, a first difference means for subtracting the second sum from the sum for that roadway with a "go" signal condition, a timer means whose rate is controlled to be inversely related to the first difference, and a logic means for skipping "go" phases for roadways and lanes whose first sum equals zero just prior to its anticipated switch from a "stop" to "go" condition.
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9. A method for controlling the timing of "go" and "stop" traffic signals at an intersection of at least two roads comprising the steps of:
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at an upstream zone sensing each approaching vehicle'"'"'s momentum and congestion factors, such congestion factors being representative of the congestion being experienced by each vehicle on each lane of each road, producing for each lane a first pulse count representing the momentum factor of each vehicle on each respective lane between the sensed zone and the intersection during a "go" signal, summing the first pulse counts for each lane for producing a first running summation for each lane indicative of aggregate momentum during a "go" signal, producing for each lane a second pulse count representing the congestion factor of each vehicle on each respective lane between the sensed zone and the intersection during a "go" signal, summing the second pulse counts for each lane for producing a second running summation indicative of aggregate congestion being experienced by each vehicle approaching the intersection on the respective lane during a "go" signal, decreasing both the first and second summations for each lane by subtracting from the respective first and second running summations the respective first and second pulse counts for vehicles on the respective lane which have passed through the intersection during the "go" signal for producing a corrected first running summation and a corrected second running summation for the respective lane, adding said corrected first running summation and said corrected second running summation for all of the lanes on a road during a "go" signal for that road for producing a first grand running summation for the road having a "go" signal, said first grand running summation being representative of the aggregate momentum and aggregate congestion of vehicular traffic on all of the lanes of said road having a "go" signal, producing for each lane of the road having a "stop" signal (the other road) a third pulse count representing the aggregate momentum factor of each vehicle on each respective lane approaching the intersection during a "stop" signal, summing the third pulse counts for each lane of said other road for producing a third running summation indicative of aggregate momentum for each lane during a "stop" signal only, decreasing said third running summation for each such lane by subtracting from said third running summation the respective pulse counts for vehicles on the respective lane which have slowed down and stopped during a "stop" signal for producing a corrected third running summation, adding said corrected third running summations for all of the lanes of said other road during a "stop" signal for that road for producing a second grand running summation for the road having a "stop" signal representative of the aggregate momentum of vehicular traffic on all of the lanes of the road having a "stop" signal, continuously comparing said first grand summation with the second grand summation during said "go" and "stop" signals, and lengthening the "go" signal relative to the "stop" signal for the respective road having the greater grand summation. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for controlling the timing of "go" and "stop" signals at an intersection of at least two roads, comprising the steps of:
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measuring each vehicle'"'"'s presence-duration and its velocity as it passes over a narrow strip of roadway located upstream from the intersection, estimating each vehicle'"'"'s momentum factor and experienced congestion factor from said presence-duration and velocity information, then summing said factors to generate first and second running sums, projecting forward both the velocity and time of arrival of each vehicle at the intersection from the sensed velocity for that vehicle and the traffic signal condition and the distance between said strip and the intersection, cancelling those momentum and congestion factors from the respective running sums for vehicles that have passed into the intersection, counting the number of vehicles stopped at the intersection during a "stop" signal condition, and then multiplying said count by a predetermined constant that establishes an equivalence between stopped and moving vehicles, as a function of the relative fuel consumption and emissions for running vehicles and for stopped vehicles with idling engines for producing the stopped vehicle factors, summing aggregate momentum and congestion factors for that roadway with a "go" signal condition for creating one grand running sum, summing together aggregate momentum and stopped vehicle factors for that roadway with a "stop" signal condition for creating a second grand running sum, and comparing said first and second grand running sums in order to create a running difference for controlling the length of the "go" signal duration relative to the "stop" signal duration for causing the roadway with the larger grand running sum to receive the longer "go" signal duration. - View Dependent Claims (22, 24, 25, 26)
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23. The method for controlling the timing of "go" and "stop" signals at an intersection, as claimed in claim 43 or 44, for the case of multiple intersections in proximity to each other, comprising the further steps of:
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sensing each vehicle'"'"'s velocity as it passes over a narrow strip of a roadway downstream from the first intersection proceeding toward a second intersection downstream from the first intersection and in proximity to the first intersection, estimating each vehicle'"'"'s downstream experienced congestion factor on said roadway from said sensed velocity, summing said downstream experienced congestion factors for the vehicles on said roadway to generate a third running sum, and subtracting said third running sum from said first grand running sum for said roadway.
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27. A traffic signal adaptive timing control system comprising:
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sensors positioned at least 100 feet upstream from an intersection for sensing the velocity and presence duration time of vehicles passing over a narrow segment of roadway near the respective sensor, a traffic signal means at said intersection for controlling the traffic at said intersection, processing means located near the intersection for multiplying the sensed velocity and sensed presence duration time of each vehicle for generating data indicative of the length of each vehicle and for multiplying said vehicle length data times the sensed velocity for each vehicle for generating data indicative of the momentum of each vehicle and for summing said momentum data for the sensed vehicles on each roadway for generating aggregate momentum data for the vehicles approaching the intersection on each respective roadway, and for generating inverse velocity factor data for each vehicle and for multiplying said inverse velocity factor data times said vehicle length data for each vehicle for generating data indicative of the congestion being experienced by each vehicle and for summing said congestion data for the sensed vehicles on each roadway for generating aggregate experienced congestion data for the vehicles approaching the intersection on each respective roadway, and for multiplying the number of vehicles forecasted to have been stopped on a respective roadway during a "stop" signal times an empirical constant representative of fuel consumption and pollution caused by a stopped vehicle relative to a moving vehicle for generating aggregate stopped vehicle data for each respective roadway near the intersection during a "stop" signal and then for progressively reducing said aggregate stopped vehicle data for the respective roadway after the signal has changed to "go" for changing said aggregate stopped vehicle data to reflect previously stopped vehicles that have cleared through the intersection, and for determining the number of sensed vehicles on each respective roadway which have passed the segment of roadway during a current predetermined time interval for generating data indicative of a tentatively identified platoon approaching said intersection on the respective roadway, transmission means connected with said sensors and associated with said processing means for forwarding sensed information from said sensors to said processing means, a traffic signal timer for controlling said traffic signal means, said processing means being connected to said timer, sum comparison means in said processing means for providing running sum comparisons of said aggregate data to determine the roadway having associated therewith a significantly larger running sum, said sum comparison means generating a control signal that stops said traffic signal timer to hold a "go" signal for said roadway having the larger running sum associated therewith, that speeds up said traffic signal timer when a roadway having a "stop" signal has the larger running sum associated therewith and that allows the timer to run at its normal rate when there is no significant difference in running sums, and said sum comparison means generating a second control signal which upon coincidence with tentative platoon identification data and a "go" signal stops said traffic signal timer for a predetermined time, and upon coincidence of tentative platoon identification data and a "stop" signal speeds up said traffic signal timer for a predetermined time. - View Dependent Claims (28)
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Specification