Estimating Path Travel-Time Reliability

The estimation of path or trip travel-time reliability is critical to any Advanced Traveler Information System. The state-of-practice procedures for estimating path travel-time reliability assume that travel times follow a normal distribution and require a measure of trip travel-time variance. The study analyzes AVI data from San Antonio and demonstrates through goodness-of-fit tests that the assumption of normality is, from a theoretical standpoint, inconsistent with field travel-time observations and that a lognormal distribution is more representative of roadway travel times. However, visual inspection of the data demonstrates that the normality assumption may be sufficient from a practical standpoint given its computational simplicity. The paper then proposes five methods for the estimation of path travel-time variance from its component segment travel-time variances. The analysis demonstrates that computing the trip travel-time coefficient of variation as the conditional expectation over all realizations of roadway segments provides estimates within 13% of field observations for both uncongested and congested conditions.

• Corporate Authors:

  Transportation Research Board

  500 Fifth Street, NW
  Washington, DC  United States  20001
• Authors:
  • Rakha, Hesham Ahmed
  • El-Shawarby, Ihab
  • Arafeh, Mazen
  • Dion, Francois
• Conference:
  • Transportation Research Board 86th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2007-1-21 to 2007-1-25
• Date: 2007

Language

• English

Media Info

• Media Type: CD-ROM
• Features: Figures; References; Tables;
• Pagination: 15p
• Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

Subject/Index Terms

• TRT Terms: Advanced traveler information systems; Analysis of variance; Automatic vehicle identification; Highway operations; Reliability; State of the practice; Traffic; Traffic congestion; Traffic data; Traffic flow; Transportation planning; Travel time
• Geographic Terms: San Antonio (Texas)
• Subject Areas: Data and Information Technology; Highways; Operations and Traffic Management; Planning and Forecasting; I72: Traffic and Transport Planning;

Filing Info

• Accession Number: 01047317
• Record Type: Publication
• Report/Paper Numbers: 07-0488
• Files: TRIS, TRB
• Created Date: Feb 8 2007 5:04PM