ADVANCED CONTROL TECHNOLOGY IN URBAN TRAFFIC CONTROL SYSTEMS BUS DETECTOR DEVELOPMENT
THE FUNCTIONAL REQUIREMENTS, BASIC DESIGN PARAMETERS AND EVALUATION ARE DISCUSSED OF A BUS DETECTOR SYSTEM DEVELOPED FOR USE IN THE URBAN TRAFFIC CONTROL SYSTEM (UTCS) NOW BEING INSTALLED IN WASHINGTON, D. C. THE BUS DETECTOR SYSTEM MAKES POSSIBLE THE SENSING OF BUSES ON THE APPROACH TO AN INTERSECTION SO THAT PREFERENTIAL GREEN EXTENSIONS WILL FAVOR THEIR MOVEMENT OVER PRIVATE VEHICULAR TRAFFIC. THE SYSTEM INCLUDES BUS-MOUNTED TRANSMITTERS, LOOP ANTENNAS BURIED IN THE ROAD AND CURBSIDE RECEIVERS. PRESENCE PULSES GENERATED BY A RECEIVER WHEN A BUS PASSES OVER THE LOOP ARE TRANSMITTED OVER LEASED TELEPHONE LINES TO THE UTCS CONTROL SITE. HERE, A CENTRAL COMPUTER PROCESSES BOTH BUS AND SEPARATELY SUPPLIED VEHICULAR DATA IN ACCORDANCE WITH A BUS PRIORITY ALGORITHM TO DETERMINE WHEN GREEN EXTENSIONS ARE TO BE GRANTED. FUNCTIONALLY, THE BUS DETECTOR MUST BE CAPABLE OF SENSING ALL BUSES APPROACHING AN INTERSECTION AT SPEEDS OF 1 TO 40 MPH. DETECTION COVERAGE MUST MINIMIZE FALSE DETECTIONS OF BUSES IN ADJACENT OPPOSING LANES AND ABORTED DETECTIONS OF SIDE-BY-SIDE OR NOSE-TO TAIL BUSES. DISTINCTION BETWEEN STOP AND THRU BUSES IS NECESSARY TO ACCOUNT FOR THEIR DIFFERENT INTERSECTION EXITING CHARACTERISTICS. ALL THIS MUST BE ACCOMPLISHED WITH RELIABLE EQUIPMENT WITH COST APPROXIMATING STANDARD VEHICLE LOOP DETECTORS. THE BUS DETECTOR CONFIGURATION DESIGNED TO MEET THESE REQUIRMENTS UTILIZES NEAR-FIELD RADIO FREQUENCY TRANSMISSIONS, A BURIED SINGLE-TURN LOOP ANTENNA, AND A STANDARD RADIO RECEIVER CIRCUIT DESIGN. LOW FREQUENCY NEAR-FIELD RADIO TRANSMISSION (APPROXIMATELY 175 KHZ) WAS SELECTED BECAUSE ITS COVERAGE PATTERN IS CONFINED SHARPLY TO A VERY LOCALIZED VICINITY AND IT OPERATES AT RELATIVELY LOW POWER LEVELS. THE 175 KHZ FREQUENCY RANGE DOES NOT REQUIRE FCC LICENSING AT THE OPERATING POWER LEVELS USED. THIS FREQUENCY RANGE IS RELATIVELY FREE OF EXTERNAL INTERFERENCE BECAUSE VERY LARGE ANTENNAS ARE NECESSARY FOR EFFECTIVE FAR FIELD TRANSMISSION. THE SINGLE TURN LOOP CONFORMS CLOSELY WITH CONVENTIONAL VEHICLE DETECTOR LOOPS, THEREBY SIMPLIFYING STREET INSTALLATION. USING STANDARD RADIO CIRCUITRY PERMITS THE USE OF A WELL-ESTABLISHED COMMERCIAL TECHNOLOGY THUS ASSURING A RELIABLE AND LOW COST PRODUCTION UNIT. /AUTHOR/
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Corporate Authors:
Urban Mass Transportation Administration
400 7th Street, SW
Washington, DC United States 20590Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC United States 20590Dist of Columbia Dept Hwys & Traffic
,Sperry Rand Corporation
Sperry Systems Management Division
Great Neck, NY United States 11020 - Publication Date: 0
Subject/Index Terms
- TRT Terms: Antennas; Buses; Computers; Electric circuits; Frequency (Electromagnetism); Green interval (Traffic signal cycle); Radio receivers; Radio transmitters; Traffic control; Vehicle detectors
- Old TRIS Terms: Circuits; Loop antennas; Traffic control systems
- Subject Areas: Highways; Operations and Traffic Management; Public Transportation;
Filing Info
- Accession Number: 00225004
- Record Type: Publication
- Source Agency: Federal Highway Administration
- Files: TRIS, USDOT
- Created Date: Mar 7 1972 12:00AM