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Research report 464 Incorporating travel time reliability in the estimation of assignment models

Published: | Category: Transport demand management , Research programme , Research & reports | Audience: General

Route choice is determined by some function of mean travel time and distance on the routes available in most traffic assignment models. Increasing traffic volumes on a route increases delay, making a particular route less desirable.

The NZ Transport Agency (2010) Economic evaluation manual allows the benefits of improved network reliability to be monetised. However, our network models are unable to provide a convenient means of calculating the road user responses to travel time variability.

Route choice is a more complex issue than a comparison of relative travel times and distance. It appears that road users are also considering travel time variability in their route choice. Variability may occur as a result of congestion in cities or on any network as a result of road geometry, a high volume of heavy vehicles on narrow steep roads, or other reasons.

This research was carried out during 2008 to 2011 using Wellington data and sought to identify a methodology that best incorporated travel time variability into route choice models. The research determined the most useful formulation for use in models and the appropriate measure of travel time variability.

Keywords: assignment, coefficient of variation, congestion index, NZ Transport Agency, reliability, route choice, travel time, variability

Publication details

  • Author:
  • Published: December 2011
  • Reference: 464
  • ISBN/ISSN: ISBN 978-0-478-38079-8 (print); ISBN 978-0-478-38078-1 (electronic)