Emergency traffic signal preempt system

• US 5,083,125 A
• Filed: 06/29/1990
• Issued: 01/21/1992
• Est. Priority Date: 06/29/1990
• Status: Expired due to Fees

• Current Assignee: Emergency Medical Systems, Inc.
• Original Assignee: Emergency Medical Systems, Inc.
• Inventors: Brown, Robert H., Scott, Richard M., Liebich, Charles R., Page, Gregory B.
• Primary Examiner(s): Crosland, Donnie L.
• Application Number:
  US07/546,510
• Time in Patent Office: 571 Days
• Field of Search: 340/906, 340/902, 340/903, 340/904, 364/424.01, 364/436, 455/67, 455/9
• US Class Current: 340/906
• CPC Class Codes: G08G 1/087 Override of traffic control, e.g. by signal transmitted by an emergency vehicle

Abstract

An emergency situation traffic signal control system, employing true radar and telemetry-based systems, which is a two-way, two frequency, full duplex transmission system. The system consists of an intersection transmitter/receiver electrically coupled to an intersection traffic signal control box and a vehicular transponder. The intersection transmitter/receiver generates an A/DCODE consisting of an access code ("ACODE") and a direction code ("DCODE"). The intersection transmitter/receiver continuously monitors the intersection by sending the A/DCODE signal in the approach directions relative to the intersection. An authorized emergency vehicle transponder approaching the intersection receives the A/DCODE, verifies the accuracy of the codes and re-transmits the DCODE, along with an optional vehicle identification code ("VID"), to the intersection transmitter/receiver for verification. If the vehicle is positively verified, control of the intersection is handed over to the vehicle by engaging valid preempt.

Claims

1. An emergency traffic signal control system, comprising:

means for generating at least an access code (ACODE), a direction code (DCODE) and a ranging signal (RPULSE);

an intersection based transmitter/receiver, electrically coupled to said means for generating said codes, said intersection based transmitter/receiver generates an RF signal and impresses said generated codes upon said RF signal and directionally transmits said RF signal as forward tones;

a vehicle based receiver/transmitter which receives said transmitted forward tones;

signal processing means, electrically coupled to said vehicle based receiver/transmitter, for processing said received forward tones and returning said received forward tones as return tones, to said vehicle based receiver/transmitter for return transmission to said intersection transmitter/receiver; and

means for validating said return tones and controlling the traffic signals in response to validated return tones and to said ranging signal, said means being electrically coupled to said intersection transmitter/receiver and to said means for generating an RF signal. PG,19

2. The emergency traffic signal control system according to claim 1, wherein said intersection transmitter/receiver and said vehicle based receiver/transmitter each further comprise a transmitter, said transmitter comprising an oscillator, a phase modulator and an amplitude modulator and a receiver, said receiver comprising an AM demodulator and an FM demodulator.

3. The emergency traffic signal control system according to claim 2, wherein phase modulator receives said ACODE and said DCODE and impresses said ACODE and said DCODE onto said RF signal from said means for generating said at least an ACODE, DCODE and RPULSE.

4. The emergency traffic signal control system according to claim 2, wherein said amplitude modulator receives said RPULSE and impresses said RPULSE onto said RF signal prior to transmission of said RF signal from said transmitter.

5. The emergency traffic signal control system according to claim 2, wherein said AM demodulator separates said RPULSE from said forward tones.

6. The emergency traffic signal control system according to claim 2, wherein said FM demodulator separates said ACODE and said DCODE from said forward tones.

7. The emergency traffic signal control system according to claim 1, wherein said signal processing means further comprises means for separating said ACODE and said DCODE from said forward tones, an addressable asynchronous receiver/transmitter, a timing generator and means for encoding signals received from said addressable asynchronous receiver/transmitter and generating said return tones.

8. The emergency traffic signal control system according to claim 7, wherein said means for separating said ACODE and said DCODE from said forward tones further comprises an FSK demodulator, said FSK demodulator receives input from vehicle based receiver/transmitter and recovers said ACODE and said DCODE from said forward tones.

9. The emergency traffic signal control system according to claim 8, wherein said addressable asynchronous receiver/transmitter receives said recovered ACODE and said DCODE from said FSK demodulator, verifies that the proper ACODE was received, and upon said verification transmits the DCODE with said vehicle identification code (VID) to said FSK modulator.

10. The emergency traffic signal control system according to claim 9, wherein said means for encoding signals received from said addressable asynchronous receiver/transmitter further comprises an FSK modulator, said FSK modulator receives said DCODE and said vehicle identification code and converts said codes to return tones, said return tones being different and distinct from said forward tones.

11. The emergency traffic signal control system according to claim 10, wherein said timing generator delays return transmission of said RPULSE by said vehicle based receiver/transmitter.

12. The emergency traffic signal control system according to claim 7, wherein said means for validating said return tones further comprises means for recovering said DCODE from said return tones, an addressable asynchronous receiver/transmitter, a valid return latch which is set in response to said addressable asynchronous receiver/transmitter matching said recovered DCODE with said transmitted DCODE in said forward tones a range gate electrically coupled to said AM demodulator of said intersection receiver and to said valid return latch and an output switch activates a valid pre-empt of the traffic signals.

13. The emergency traffic signal control system according to claim 12, wherein said means for recovering said DCODE from said return tones further comprises an FSK demodulator.

14. The emergency traffic signal control system according to claim 12, wherein said range gate is open in response to a maximum pre-selected distance in which a vehicle can control the intersection.

15. The emergency traffic signal control system according to claim 14, wherein said output switch is activated when the range gate is open when the RPULSE arrives at the range gate and the valid return latch is set.

16. An emergency control system for traffic signals at intersections and a main traffic controller associated with the traffic signals, comprising:

means for generating at least a digital access code (ACODE), a digital direction code (DCODE) and a digital ranging signal (RPULSE);

an intersection based transmitter/receiver, comprising a transmitter, said transmitter further comprising an oscillator, a phase modulator and an amplitude modulator, and a receiver, said receiver further comprising an AM demodulator and an FM demodulator, said transmitter/receiver being electrically coupled to said means for generating said codes, wherein said intersection based transmitter/receiver generates an RF signal, said phase modulator receives said ACODE and said DCODE from said means for generating said codes and impresses said ACODE and said DCODE onto said RF signal, and said amplitude modulator receives said RPULSE from said means for generating said codes and impresses said RPULSE onto said RF signal prior to transmission of said impressed RF signal from said transmitter as forward tones;

a vehicle based receiver/transmitter, comprising a transmitter, said transmitter further comprising an oscillator, a phase modulator and an amplitude modulator, and a receiver, said receiver further comprising an AM demodulator and an FM demodulator, said receiver/transmitter receiving said transmitted forward tones;

signal processing means, electrically coupled to said vehicle based receiver/transmitter, for processing said received forward tones and returning said received DCODE to said vehicle based receiver/transmitter for return transmission to said intersection transmitter/receiver; and

means for validating said return tones and controlling the traffic signals in response to validated return tones and to said ranging signal, said means being electrically coupled to said intersection transmitter/receiver and to said means for generating an RF signal and further comprising means for recovering said DCODE from said return tones, an addressable asynchronous receiver/transmitter, a valid return latch, which is set in response to said addressable asynchronous receiver/transmitter matching said recovered DCODE with said transmitted DCODE in said forward tones, a range gate electrically coupled to said AM demodulator of said intersection receiver and to said valid return latch and an output switch activates a valid pre-empt of the traffic signals.

17. The emergency traffic signal control system according to claim 16, wherein said AM demodulator separates said RPULSE from said forward tones.

18. The emergency traffic signal control system according to claim 16, wherein said FM demodulator separates said ACODE and said DCODE from said forward tones.

19. The emergency traffic signal control system according to claim 16, wherein said signal processing means further comprises an FSK demodulator, an addressable asynchronous receiver/transmitter, a timing generator and an FSK modulator.

20. The emergency traffic signal control system according to claim 19, wherein said FSK demodulator receives input from said intersection based receiver/transmitter and recovers said ACODE and said DCODE from said forward tones.

21. The emergency traffic signal control system according to claim 20, wherein said addressable asynchronous receiver/transmitter receives said recovered ACODE and said DCODE from said FSK demodulator, verifies that the proper ACODE was received, and upon said verification transmits the DCODE with said vehicle identification code (VID) to said FSK modulator.

22. The emergency traffic signal control system according to claim 21, wherein said FSK modulator receives said DCODE and said vehicle identification code and converts said codes to return tones, said return tones being different and distinct from said forward tones.

23. The emergency traffic signal control system according to claim 21, wherein said timing generator delays return transmission of said RPULSE by said vehicle based receiver/transmitter.

24. The emergency traffic signal control system according to claim 16, wherein said means for recovering said DCODE from said return tones further comprises an FSK demodulator.

25. The emergency traffic signal control system according to claim 16, wherein said range gate is open in response to a maximum pre-selected distance in which a vehicle can control the intersection.

26. The emergency traffic signal control system according to claim 25, wherein said output switch is activated when the range gate is open, the RPULSE arrives at the range gate and the valid range latch is set.