Feasibility of Voluntary Reduction of Private Car Use

Abstract

Many countries are today facing substantial environmental and societal costs of private car use such as congestion, noise, and air pollution. Transport authorities therefore implement various policy measures that aim to modify or reduce private car use. These are generally referred to as Travel Demand Management (TDM) measures. In this research report we propose a classification of the various TDM-measures, encompassing the specific characteristics of each, how the various measures may be distinguished from each other and to what extent they may interact, as well as how effective they are in modifying or reducing private car use. A theoretical framework is proposed next, to account for how the TDM measures impact on car users' change in travel behaviour. The theoretical framework posits that, if a change goal is set, it is followed by forming plans to attain the set goal (e.g., to change from using the car to using alternative modes). A principle of cost-minimization is proposed that describes how car users incrementally implement plans to achieve their set goals. A review of voluntary travel-behavior change (VTBC) programs shows that in general the VTBC-related TDM measures are effective. Yet, it is still unclear whether these positive effects are long-term. Furthermore, the positive effects are apparently only observed for motivated (and self-selected) participants and not even necessarily for all of them unless some facilitating conditions are fulfilled. However, the VTBC measures meet with higher public acceptance, are politically feasible, and cost-effective. It is argued that more research is needed to answer the questions of when and why VTBC measures work, wherein also a closer investigation into which individual and situational factors it is that generates the positive effect.