Effects of speed limits on travel time variability of freeway corridors

Over the last two decades travel time reliability has become an important aspect of transportation system performance. One group of factors affecting travel time variability is traffic control measures, such as speed limits. Knowledge about the influence of speed limits on travel time variability can help to improve travel time reliability. An analysis of a large database of travel times on two freeway corridors shows that travel time variability is strongly affected by speed limit. Above a certain threshold inflow, Critical Transition inFlow CTF lambda1, speed limit contributes to more reliable travel time. Below CTF lambda1, speed limit, however, leads to higher travel time variability. Speed limit results in higher CTF lambda1 due to the fact of homogenization of traffic flow and the prevention of traffic breakdown on the use of dynamic speed limit. It is also found that tight speed limit (towards lower value of speed limit) not only increases the 10th percentile travel time, but also significantly results in a higher 50th percentile travel time. As a result of this study, the control parameter of speed limit should be considered under different traffic demand from travel time reliability point of view. For the covering abstract see ITRD E140665.

  • Authors:
    • TU, H
    • VAN LINT, H
  • Publication Date: 2007


  • English

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  • Accession Number: 01155241
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Apr 23 2010 10:58AM