It is suggested that the fixed trip matrix assumptions used in forecasting response to new road capacity tends to understate scheme benefits for uncongested conditions but overstate benefits for congested conditions. As part of a study carried out for the Transport and Road Research Laboratory (TRRL) to establish a more accurate forecasting method the authors carried out a survey to gauge professional opinion on likely responses. Consultants, local authority engineers, academics and Department of Transport, were questioned on responses to four notional schemes including a new rural motorway, a bypass, an orbital urban motorway and junction capacity improvements. For each scheme the respondent was asked to estimate the relative importance of reassignment, modal transfer, redistribution, increased trip frequency, new trips and exogenous traffic growth. With reassignment and exogenous growth generally agreed to be the most dominant responses, a significant amount of traffic was expected from other sources. The authors conclude that fixed matrix methods do not take account of these and that their use is questionable in the current roads programme. (TRRL)

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    Reed Business Information, Limited

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  • Authors:
    • Bonsall, P
    • MACKIE, P
    • Pells, S
  • Publication Date: 1990-9-6


  • English

Media Info

  • Pagination: p. 18-19
  • Serial:
    • Volume: 174
    • Issue Number: 5111
    • Publisher: Hemming Group, Limited
    • ISSN: 0039-6303

Subject/Index Terms

Filing Info

  • Accession Number: 00617643
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Nov 30 1991 12:00AM