The primary objective of this report is to introduce psychological factors into the understanding and modeling of the mode choice process. Substantial evidence shows that traditional models of mode choice, which emphasize time and costs and a rational decision-making process, are inadequate representations of how people make transportation choices. Still, they are the primary methods practitioners use for transportation planning. The challenge is to develop models that can adequately represent qualitative factors and that also can be used for policy analysis and forecasting.
Three approaches to modeling mode choice were identified in this study: (1) rational, economic models - traditional models that employ measurements of actual time and cost and assume that people are utility maximizers; (2) models employing attitudinal and perceptual variables - the application of psychological theories and psychometric techniques to quantify factors that are basically qualitative; and (3) activity-based travel analysis - these start with the assumption that transportation choices are merely a means to engage in activities and take into account spatial, household, and other constraints.
Each approach has its advantages and disadvantages. A successful method for modeling and understanding mode choice will borrow from each of these approaches.
The report discusses several important issues in extending our understanding of the mode choice process. Those discussions can be condensed into five main themes: (1) perceptions of time and cost are more important than actual time and cost; (2) qualitative variables are important, but they are interrelated and affect perceptions of time and cost; (3) demographic variables are relatively unimportant except as they relate to mode accessibility; (4) values, beliefs and psychological needs enter into the mode choice process; and (5) the formation and breaking of habit is the key to understanding the cognitive processes involved in transportation choices.