STREET TRAFFIC SIGNAL SYSTEM

• US 3,833,881 A
• Filed: 05/26/1972
• Issued: 09/03/1974
• Est. Priority Date: 09/30/1971
• Status: Expired due to Term

• Current Assignee: Gerd Pfeffer, Peter Drebinger
• Original Assignee: Gerd Pfeffer, Peter Drebinger
• Inventors: Drebinger, Peter, Pfeffer, Gerd
• Primary Examiner(s): Cooper, William C.
• Application Number:
  US05/257,257
• Time in Patent Office: 830 Days
• Field of Search: 340/31A,31R
• US Class Current: 340/920
• CPC Class Codes: G08G 1/08 according to detected number or speed of vehicles

Abstract

A street traffic signalling system having signal units disposed at the respective sides of an intersection and controllable in response to traffic detectors also disposed at the sides of such intersection, a measuring device being provided for each traffic flow monitored by a traffic detector, with each measuring device being adapted to evaluate and store criteria representative of the occupied or unoccupied condition of the associated detector, and to effect a signal change when predetermined occupiedunoccupied conditions exist representing an optimum period duration, or when the occupied periods reach a magnitude representing traffic congestion. The respective measuring devices may be so coupled that related traffic flows are controlled in dependence upon optimum conditions at all flows so related, or when congestion is indicated with respect to any one such flow.

Claims

1. In a street traffic signalling system having signal units disposed at the sides of an intersection and controllable in response to traffic detectors also disposed at the sides of such intersection, the combination of a measuring device, having at least one storage means, for each traffic flow monitored by a traffic detector, with the storage means being operable, in response to operation of said traffic detectors, to receive signals respectively representing occupied and unoccupied periods reported by the associated detector, means for summing the signals representing occupied and unoccupied periods of the associated detector, and means responsive to a predetermined summing value, operative to provide an optimum '"'"''"'"''"'"''"'"'go'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' period of an associated signal unit, or a predetermined control of the duration of the '"'"''"'"''"'"''"'"'go'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' period in the presence of a predetermined comparison relationship, in dependence upon predetermined signals, received by one of such related storage means from the associated detector, representing traffic congestion at such detector.

2. A system according to claim 1, wherein said storage means of a measuring device is operative to determine the duration of a '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'go'"'"''"'"''"'"''"'"' period irrespective of optimum periods, in the presence of traffic congestion, represented by a predetermined summing, in dependence upon occupation of an associated detector and is arranged to receive signals, in the form of voltages, representing occupied and unoccupied periods, and including means for supplying such voltages thereto with opposite identifying polarities, with a congestion signal being derived in said storage means as a difference between said voltages of opposite polarities.

3. A system according to claim 1, wherein such storage means of a measuring device is operative to determine the duration of the optimum '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'go'"'"''"'"''"'"''"'"' period, and is arranged to receive voltages representing occupied and unoccupied periods, and including means for supplying such voltages thereto with opposite identifying polarities, with the optimum period being derived in said storage means as a difference and means defining an operative threshold for determining the voltage representative of such optimum period.

4. A system according to claim 3, wherein each measuring device has two such storage means, the second of which such storage means is operative to determine the duration of a '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'go'"'"''"'"''"'"''"'"' period, irrespective of optimum periods, in the presence of traffic congestion, represented by a predetermined summing value in dependence upon occupation periods of an associated detector, and is arranged to receive voltages representing occupied and unoccupied periods, and including means for supplying such voltages thereto with opposite identifying polarities, with a congestion signal being derived in said storage means as a difference.

5. A system according to claim 1, comprising in further combination, blocking means for the respective storage means arranged to prevent the stored content of such storage means from exceeding a threshold value, preferably zero value.

6. A system according to claim 1, wherein the respective storage means include a chargeable capacitor as the storage member, and an operational amplifier, the output voltages of the latter being stored in said storage member.

7. A system according to claim 1, comprising in further combination, adjustable means for independently adjusting relative voltages representative of occupied and unoccupied periods, to enable desired proportionate evaluation of occupied and unoccupied periods.

8. A system according to claim 1, comprising in further combination, means linking the measuring devices of respective selected traffic flows whereby optimum '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'go'"'"''"'"''"'"''"'"' time of the selected traffic flows is terminated only when the optimum periods for such selected traffic flows have been reached.

9. A system according to claim 8, wherein said linking means comprises AND gates.

10. A system according to claim 8, comprising in further combination, means linking the measuring devices of respective selected traffic flows whereby termination of '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'go'"'"''"'"''"'"''"'"' periods for such selected traffic flows will take place in the presence of a congestion signal at any one of the measuring devices for such selected flows.

11. A system according to claim 10, wherein said linking means comprises OR gates.

12. A system according to claim 1, wherein means is provided for controlling the operation of the respective measuring devices whereby the storage means thereof is inoperable when the associated signal unit is '"'"''"'"''"'"''"'"'red'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'stop'"'"''"'"''"'"''"'"' and operable when such signal unit is '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'go.'"'"''"'"''"'"''"'"'

13. A system according to claim 12, wherein each of said storage means comprises a storage capacitor and said operation-determining means comprises shunt contact adapted to shunt the associated storage capacitor when the associated signal unit is '"'"''"'"''"'"''"'"'red'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'stop'"'"''"'"''"'"''"'"'.

14. A system according to claim 1, wherein means is provided for terminating a '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'go'"'"''"'"''"'"''"'"' period after a predetermined maximum time, independently of the determination of the end of an optimum period.

15. A system according to claim 1, wherein the respective traffic detectors comprise inductive loops of about the same length as the average personal car length, and disposed at a distance of about such a car length from the associated stop line at the intersection.

16. A system according to claim 4, wherein each measuring device is provided with two storage means, each of which comprise a storage capacitor, respectively, designated as '"'"''"'"''"'"''"'"'optimum'"'"''"'"''"'"''"'"' and '"'"''"'"''"'"''"'"'congestion'"'"''"'"''"'"''"'"' capacitors, each capacitor being operatively shunted by an operational amplifier, a blocking diode, and operation-determining shunt contacts, comparing means at the output side of each capacitor for comparing the charge thereon with a threshold voltage, adjustable means associated with each comparing means for selectively supplying a threshold voltage thereto, means at the input side of each capacitor and amplifier and including cooperable contacts for selectively supplying voltages of predetermined values and polarities to the associated capacitor and amplifier, means for selectively actuating said shunt contacts to open the same when the traffic unit associated therewith designates a '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'go'"'"''"'"''"'"''"'"' period and closed when a '"'"''"'"''"'"''"'"'red'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'stop'"'"''"'"''"'"''"'"' period is designated thereby, and means for selectively actuating said input contacts in dependence upon the or absence of a signal from the associated detector.

17. A system accOrding to claim 16, in which two traffic flows are to be linked, wherein the output of the comparing means associated with '"'"''"'"''"'"''"'"'optimum'"'"''"'"''"'"''"'"' capacitors of the measuring devices of such linked flows, is connected with a respective input of an AND gate, the output of which and the outputs of the other comparing means associated with the '"'"''"'"''"'"''"'"'congestion'"'"''"'"''"'"''"'"' capacitors of such measuring devices, conducted to respective inputs of an OR gate, the output signal of which is adapted to effect termination of a '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'go'"'"''"'"''"'"''"'"' period of the associated signal units.