Gaudry, M., and de Lapparent, M. (2015)

Attitudes to Distance, Time and Cost in Logit Transport Choice Models

During the last 20 years, a distance variable has sometimes been added to specifications of Logit utility functions that already included travel time and cost variables long assumed in theory and practice to embody the impeding effect of distance on transport demand. We briefly recall some milestones of this seemingly superfluous enrichment of modeling practice and propose to understand it as allowing for the expression of an “Attitude to Distance” (or DA) distinct from the “Attitude to Time or Cost” level of service outcomes. The framework adopted to document this split role of distance, a duality not entirely absent from common language, is the Multino- mial Box-Cox Logit model where, in the hope of improving estimates of Values of Travel Time Savings, distance raised to a simple power has recently often been introduced in interactions with the time and cost terms. Under the DA interpretation, the new power parameters of distance reveal an optimistic, pessimistic or neutral behavior towards distance distinct from any attitudes to the level of service variables themselves. In alternate specifications of utility functions based from the start on price, speed and distance variables, the self-standing distance term can also be re-interpreted as comprising a “Distance Attitude” component in addition to an impedance effect.