There are two general approaches to travel demand analysis currently being suggested: one the widely used “Urban Transportation Planning process,” and the other the use of “Direct Demand Models.” Their general forms, strengths, and weaknesses are sketched briefly here, and some problems common to both approaches are investigated. These include the limitations imposed by the single period, static, partial equilibrium nature of the analysis, and the problems raised by the possible existence of multiple equilibria within that framework.
The paper advocates research in several directions which would help to alleviate the problems in current procedures, and which also promises to yield some policy guidelines as research progresses. These are the investigation of peaking patterns and the forces behind them, the quantitative representation of more dimensions of traveler experience than are currently being analyzed, the analysis of different socio-economic stratifications, the inclusion of auto ownership decisions into the travel demand prediction process, and the development and comparison of alternative structural formulations for determining passenger demand. It is suggested that, for the time being, analyses along the proposed lines should be conducted in connection with specific, relatively small-scale transport projects as opposed to a modeling effort which attempts to tackle all of the analysis problems simultaneously.