Impact of Spatial Segmentation on Travel Time Reliability Performance Measures

It can be shown that measures of variability in corridor travel time, unlike average values, depend in part on how that corridor is broken up into segments for measurement. This affects all agencies that use such metrics in performance measurement and/or project selection, especially all state departments of transportation (state DOTs) and large metropolitan planning organizations (MPOs) subject to the requirements of performance management spelled out in such federal-aid surface transportation requirements as the Moving Ahead for Progress in the 21st Century Act (MAP-21). The proposed research will develop a series of guidelines and best practices suitable for implementation by transportation agencies. Step-by-step processes will be developed, and guidance for implementation (including analysis tools) will be provided. Only limited research has been conducted on this subject to date. One recent report (cited on page 3) evaluated the impact of spatial segmentation on arterial system delay measures using several data sets from southeastern Virginia. Compared to industry standard TMC road segments, custom segments based on engineering judgment (such as homogeneous traffic volume, speed limit, number of lanes, signal density, etc.) decreased network delay by −3.4% and reliability index measures by 0.7% to 1.9% (using Global Positioning System (GPS) data from INRIX). Use of very long segments, such as the entire corridor in each direction, noticeably averaged out congestion and decreased the delay by 29% and reliability index measures by 2.3% to 4.9%. The corresponding reductions using the National Performance Measures Research Data Set (NPMRDS) were 43% for delay and 5.7% to 9.5% for reliability index measures. This study was focused on arterial roads, and it is unclear if those results would translate to other areas or to freeway facilities. The objective of this research is to determine the statistical implications of current methods for determining travel time and its reliability and propose a set of corresponding measures, including consideration for segmentation, that are suitable for roadway systems. A recommendation on how to compare travel time reliability among corridors, regions, or even states can facilitate communications of this measure and is an expected outcome from this project. In carrying out this research, attention should be given to Federal Highway Administration work with the I-95 Corridor Coalition and work undertaken by the AASHTO Committee on Performance Based Management.


  • English


  • Status: Proposed
  • Funding: $150000
  • Contract Numbers:

    Project 08-143

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Goldstein, Lawrence

  • Start Date: 20200520
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01739639
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 08-143
  • Files: TRB, RIP
  • Created Date: May 18 2020 3:05PM