This paper reports on a study that compared the efficacy of Schwartz’s norm-activation theory and Ajzen’s Theory of Planned Behaviour (TPB) in predicting intentions to reduce car use in favour of less polluting modes for travel to a UK university. Although the norm-activation constructs could not be empirically differentiated in line with Schwartz’s original formulation of the model, intentions were better predicted by awareness of consequences and a combined responsibility and obligation measure than by the TPB. All three TPB variables (attitude toward the behaviour, perceived behavioural control (PBC) and subjective norm) were also significant predictors of intentions, but their lesser explanatory power suggests that respondents’ decisions to reduce car use in favour of alternative modes were motivated more by altruistic concerns than by self-interest. An integrated model, using constructs from both norm-activation theory and the TPB, was also tested. The responsibility and obligation measure was again a statistically significant predictor of intentions, along with the TPB’s PBC construct. This model provided better prediction of intentions than those based on either individual theory, suggesting that neither fully captures the range of salient concerns behind decisions to reduce car use. A further model was tested, which combined psychological predictors with socio-demographic and physical-contextual influences. These included age, gender and income, along with the number of other people carried in the car on university trips and whether respondents combined their university travel with other trips, such as shopping, or dropping off children. Prediction of intention was improved again by addition of these situational influences. Discussion is provided, arguing that prediction of intentions to switch travel modes should take account of both altruistic and more personal motivations, as well as situational factors.