The aim of this thesis was to study determinants of a readiness for pro-environmental travel behavior in households. Four empirical studies were conducted examining reduction in car use (Study I), acceptability of transport policy measures (Study II and III), and behavioral adaptations in response to travel demand management (TDM) measures (Study IV). In Study I, the aim was to interrupt habitual car use by means of a deliberation intervention and to examine the importance of moral motivation (i.e., personal norm) for car use reduction. Results showed that, as a result of the intervention, car use was mainly reduced among car users with a strong car use habit and a strong moral motivation to reduce car use. The aim of Study II was to examine factors important for the acceptability of three TDM measures: raised tax on fossil fuel, improved public transport, and an information campaign. The results demonstrated the importance of general environmental beliefs (i.e., pro-environmental orientation, problem awareness, personal norm, and willingness to reduce car use) and policy specific beliefs (i.e., perceived impact on freedom to choose travel mode and own car use, perceived effectiveness, and perceived fairness) for the acceptability of the measures. Furthermore, personal norm was found to be particularly important for the acceptability of raised tax and the information campaign, whereas problem awareness was more important for the acceptability of improved public transport. Following up on Study II, the purpose of Study III was to examine the acceptability of single and combined transport policy measures, more specifically, raised tax on fossil fuel, improved public transport, subsidies of renewable fuel, a package of raised tax on fossil fuel and improved public transport, and a package of raised tax on fossil fuel and subsidies of renewable fuel. General environmental beliefs (i.e., pro-environmental orientation, problem awareness, personal norm, and willingness to act) and policy specific beliefs (i.e., perceived effectiveness and perceived fairness) were found to be important for the acceptability of the measures. Moreover, personal norm was particularly important for the acceptability of raised tax on fossil fuel and the packages, while problem awareness was more important for the acceptability of improved public transport and subsidies of renewable fuel. The aim of Study IV was to examine the behavioral adaptations, more specifically, the expected car use reduction, in response to three hypothetical TDM measures: raised tax on fossil fuel, improved public transport, and a package of raised tax on fossil fuel and improved public transport. Furthermore, factors important for the expected car use reduction were analyzed. Results showed that a combination of the measures was expected to lead to a larger car use reduction compared to the single measures, and the most commonly chosen reduction strategies were more efficient car use and changing travel mode. Moreover, internal motivational factors, such as personal norm, and the perceived personal impact of the measures were important for expected car use reduction in response to the measures.