The paper comments on two of the aspects of traffic flow: capacity and speed. It draws on results gained from an ongoing investigation into the operation of the M6 motorway in the West Midlands as a part of the M5/M6 traffic management study. Two means of data collection and analysis have been used and are briefly described. Video recordings of traffic can be analysed by means of an event recorder. Automatic traffic classifier data yielding details of vehicle type and speed can be analysed by appropriate software. Methods of defining and estimating capacity are discussed and the relationship between hourly and short-term capacity is commented on. The paper discusses a number of detailed aspects of traffic flow: the stability along a length of road of short-term variations in traffic flow; headway distributions at flows near capacity; flow perturbations caused by merging manoeuvres; the characteristics of flow breakdowns, the problems of clearing such breakdowns and their effect on throughput. The effect on both capacity and speed of adverse weather conditions is also commented on. The paper concludes that an absolute value of capacity for a length of road is difficult to determine and that short-term flow fluctuations reduce the potential efficiency of traffic flow. For the covering abstract of theseminar see TRIS 450556. (TRRL)

  • Availability:
  • Supplemental Notes:
    • Proceedings of Seminar L, Traffic Operation and Management; Held at the 12th PTRC Summer Annual Meeting, University of Warwick, England, From 10-13 July 1984, Volume P, 254.
  • Corporate Authors:

    PTRC Education and Research Services Limited

    110 Strand
    London WC2,   England 
  • Authors:
    • Keen, K G
  • Conference:
  • Publication Date: 1984

Media Info

  • Features: Figures; References;
  • Pagination: p. 25-39

Subject/Index Terms

Filing Info

  • Accession Number: 00450561
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • ISBN: 086050-137-X
  • Files: ITRD, TRIS
  • Created Date: Aug 27 2004 9:56PM