This is the first of two papers describing a detection system which has been developed and evaluated to enable buses to take priority at signal - controlled junctions. In this method the start of the green period at the traffic signals is advanced, or its termination delayed, in response to the demands of buses approaching the junction. The arrival of a bus on an approach produces a 'bus demand' in the traffic signal controller, which is normally of a higher priority than other stored demands, so that the bus receives right of way. If the traffic signals are already at green as the bus approaches, then a 'bus extension' is generated which prolongs the green period, which if necessary can exceed the normal maximum running period. Appropriate safeguards are built into the control system. The system comprises two parts (1) a unit mounted under the bus and powered from either the bus electrical system or its own batteries (2) a roadside equipment, which consists of a buried loop of wire connected to an electronic unit through a feeder cable. Practical considerations indicate that the vehicle unit can be mounted in almost any convenient position, with certain reservations, such that the unit has an uninterrupted view of the road, and preferably as near the front of the vehicle as possible if optimum priority timings are to be achieved. The construction of the roadside equipment is compatible with that of normal vehicle detectors, such that it can be mounted either in the controller case or in a separate roadside housing in the spacings available for vehicle detector equipments. The design and operation of both parts of the system are described in this paper, and evaluation trials are described in the second paper. /TRRL/

  • Availability:
  • Corporate Authors:

    Printerhall Limited

    29 Newmart Street
    London W1P 3PE,   England 
  • Authors:
    • Dow, I M
  • Publication Date: 1977-1


  • English

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Filing Info

  • Accession Number: 00156448
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: Analytic
  • Files: ITRD, TRIS
  • Created Date: Oct 13 1977 12:00AM