Developing a Model of Travel Time Variability for Congested Motorways

This paper will discuss how the topic of Travel Time Variability (TTV) is receiving increasing attention in a number of countries. However, while some progress has been made on the valuation of TTV, significant problems remain in predicting the levels of TTV that will occur in given circumstances. If the TTV benefits of improvements are to be incorporated in the appraisal process, it will be essential to be able to reflect the impact of policies on TTV. Motorways are particularly susceptible to TTV under congested conditions. Whereas under normal operating conditions TTVs offer much shorter travel times than the standard road network, they are more vulnerable to capacity problems because of their limited entry and exit points. Information systems can alleviate these problems to some extent, but a better understanding of the contributing factors to TTV is required. One of the key elements relates to the occurrence of “flow breakdown”, a term which is quite widely used, but not usually clearly defined. This appears to be a partly stochastic phenomenon, in that essentially similar levels of demand do not necessarily lead to the same outcomes. In order to conduct a thorough investigation a large amount of high quality data is needed. Most of the current authors were engaged on a previous project which specified a careful data collection process on a 12 Km highly congested section of the M6 Motorway near Birmingham in 2003. Under the auspices of the United Kingdom Highways Agency, they have now re-grouped with the intention of analyzing the data. The aim is to develop appropriate supply models that can reflect what happens, on average, for a given profile of demand during the course of the day, and, subsequently, to use this model to allow for stochastic effects, both in demand and supply, in order to model TTV. Two different approaches are being taken to the supply model, one is an aggregate level model at the link level, while the other involves the use of microsimulation using PARAMICS software. Both approaches are dynamic in concept and allow for variation in demand levels in 5-minute intervals. This paper will explain the approaches taken and evaluate their success, both in relation to the ability to replicate the observed travel times, and their ability to identify the different components of TTV.

• Record URL:
  https://aetransport.org/past-etc-papers/conference-papers-pre-2009/conference-papers-2010
• Corporate Authors:

  Association for European Transport (AET)

  1 Vernon Mews, Vernon Street, West Kensington
  London W14 0RL,    
• Authors:
  • Bates, John
  • Black, Ian
  • Fearon, John
  • Gilliam, Clive
  • Drury, Craig
• Conference:
  • European Transport Conference, 2010
  • Location: Glasgow Scotland, United Kingdom
  • Date: 2010-10-11 to 2010-10-13
• Publication Date: 2010

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; Maps; References;
• Pagination: 19p
• Monograph Title: European Transport Conference, 2010 Proceedings

Subject/Index Terms

• TRT Terms: Highway operations; Microsimulation; Traffic congestion; Traffic data; Traffic flow; Traffic simulation; Travel time
• Identifier Terms: Paramics (Computer program)
• Uncontrolled Terms: Travel time variability
• Geographic Terms: United Kingdom
• Subject Areas: Data and Information Technology; Highways; Planning and Forecasting; I72: Traffic and Transport Planning;

Filing Info

• Accession Number: 01353913
• Record Type: Publication
• Files: TRIS
• Created Date: Oct 19 2011 12:52PM