Travel Time Budgets: A Reassessment of the Concept and Its Empirical Evidence

In their desire to detect and establish stabilities or regularities in human behavior, transportation planners and economists have investigated the hypothesis that some form of constant expenditure on travel exists. The concept of travel time budgets has received substantial attention recently. This paper provides a critical view of both the concept and the empirical evidence. Three major issues are investigated in this paper: (1) computing travel time for all persons leads to different conclusions than computations based on travelers only; (2) results differ depending on whether reported or “objective” travel times are considered; and (3) the comparison of travel time budgets and trip rates shows that trip rates are at least as stable as travel time budgets. This paper proposes the study of human activity patterns as an alternative concept in order to explore regularity and stability in human behavior. Groups of people with similar activity patterns are investigated under the hypothesis that they spend similar amounts of time on travel and that would imply that different travel time budgets exist for different population groups.