Changes of Private Car Use in Response to Travel Demand Management

In times when reduction and changes in private car use is on the political agenda in urban areas, there is a need to better understand and forecast the process of change in car use. Traditional conceptualizations of travel choice in equilibrium may be insufficient to this end and need to be complemented. An alternative theoretical framework is therefore proposed based on goal setting and self-regulation theory in social psychology with the aim of analyzing responses to travel demand management (TDM) measures targeting reduced or changed car use. Such measures are assumed to lead to that car users set car-use reduction or change goals followed by planning of how to implement and implementing changes in car use to reach the goals. It is hypothesized that choices among change options are made sequentially according to a satisficing principle of minimizing psychological costs. As implied by an operationalization of this hypothesis, the result of a survey indicate that choices of mode switching correlate the strongest with the size of the car-use reduction goal, activity/trip suppression the next strongest, and efficient car use (trip chaining, car pooling, and choice of closer destinations) the weakest. The results of two additional followup surveys show that choice of number and frequency of adaptation alternatives as expected increase with the size of the car-use reduction or change goal. Taken together the results also suggested, however, that costs and effectiveness of adaptation alternatives may vary with trip purpose, the particular travel demand management measure, and household characteristics. Further research needs to incorporate such factors.