Assessing measures of transit travel time variability and reliability using AVL data

Transit reliability has been identified as one of the most important determinants of service quality. A number of measures of travel time reliability (TTR) that concern the variation of travel time (TT) in relation to an expected value, and travel time variability (TTV), the degree of variation, have been proposed. However, few applications have occurred in the transit industry, and no consensus exists as to which measures to adopt. This paper applies various TTV/TTR measures to a transit automatic vehicle location (AVL) system TT database to explore which measures might be preferred in the transit industry. The results suggest that, in general, there is no significant difference in TTV/TTR outcomes between the measures tested. Where variations emerge, it is due to the 'sensitivity' of measures to outliers in the data series. The buffer index and the coefficient of variation are recommended to measure TTR and TTV, respectively, mainly on the basis of the approach to measurement, which provides additional information to users and planners. A significant finding is that the selection of time interval length over which TT observations are aggregated for analysis of TTR/TTV can critically affect the measure outcomes. Shorter interval selection is recommended. Suggestions for future research in this field are made.


  • English

Media Info

  • Pagination: 10p
  • Monograph Title: Transportation Research Board 87th Annual Meeting compendium of papers DVD, January 13-17, 2008, Washington, DC

Subject/Index Terms

Filing Info

  • Accession Number: 01385018
  • Record Type: Publication
  • Source Agency: ARRB
  • Files: ATRI
  • Created Date: Aug 22 2012 6:29PM