The increasing requirement for equipment which would record and classify the characteristics of passing vehicles, rather than just provide an accumulative count, led to the placing of a contract by the Transport and Road Research Laboratory for the development of a microprocessor-based vehicle classifier on the basis of a software flow chart which had been developed successfully by the laboratory for use with a commercial mini computer. The inputs to the required system were defined as four lanes, each with two loop detectors and one axle detector. The two loop detectors would supply two accurate inputs which would enable the speed of the vehicle to be determined. From either one of the loop detectors the occupancy time, coupled with the derived speed and length of loop, would provide the total length of the vehicle. The axle detector would provide a means of determining the individual wheelbases of the vehicle and in some special cases allow the processor to locate the front and rear overhangs individually. In addition, it was decided to require one spare input line for each lane. The authors describe the fulfilment of this requirement, which resulted in the production of a 'one-off' vehicle classifier unit which included all the software development required for full-scale production of such equipment. Existing hardware of known reliability was used. All the hardware components for the system were initially assembled into one complete unit, and the allocation of the components is described. The development background to the software is discussed, and information is provided on software features and operation. In normal operation, without any vehicle over the sensor area, the microprocessor has available approximately 70000 meaningful instructions per second. Owing to the extensive use of input and output buffering, the processor is able to deal with up to 10 vehicles per second at the input sensors, and its output is only limited by the speed of the data terminal available. /TRRL/

  • Availability:
  • Corporate Authors:

    Printerhall Limited

    29 Newmart Street
    London W1P 3PE,   England 
  • Authors:
    • Tuthill, R D
  • Publication Date: 1978-3

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Filing Info

  • Accession Number: 00189185
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Mar 28 1979 12:00AM