Testing the constant commuting time hypothesis amid substantial changes to transportation and land use: case study of Portland, Oregon 1994-2011

There have been numerous theoretical and empirical transportation research contesting the stability of travel time over time (1–3). The constant travel time budget hypothesis posits that people adjust trip frequencies and duration, shift across modes, and locators sort through locations so that their travel time is within a constant budget. There is a discrepancy between studies applying aggregate analysis and those with disaggregate analysis (1, 2) and difference in data collection may have contributed to different conclusions reported in the literature. This study conducts both aggregate and disaggregate analyses with two travel surveys of the Portland region conducted in 1994 and 2011, respectively. The authors employ descriptive analysis and t-tests to compare aggregate commuting time between the two years and estimate regression models to explore factors affecting disaggregate commuting time at the individual trip-level. Another question of particular interest is: does commuting time remain stable after transportation and land use system go through substantial changes like Portland, OR between 1994 and 2011? The authors' study indicate that average commuting time, along with average commuting distance, increased slightly from 1994 to 2011, as the mode share has shifted away from driving during this period. The growth in shares of non-driving modes, the speed of which are slower than driving, coupled with increased travel distance, contributes to the small increase in average commuting time. The authors' analysis also indicates that average travel speed has improved for transit riders, as well as drivers, contradicting early research that claims public transit investment has worsened congestion in Portland.

  • Supplemental Notes:
    • This paper was sponsored by TRB committee ADB10 Standing Committee on Traveler Behavior and Values.
  • Corporate Authors:

    Transportation Research Board

  • Authors:
    • Yang, Huajie
    • Wang, Liming
  • Conference:
  • Date: 2019


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 9p

Subject/Index Terms

Filing Info

  • Accession Number: 01697605
  • Record Type: Publication
  • Report/Paper Numbers: 19-02447
  • Files: TRIS, TRB, ATRI
  • Created Date: Dec 7 2018 9:32AM