Policymakers may be reluctant to implement pro-environmental policies that the public find unacceptable, such as policies intended to reduce car use. It is, therefore, essential to understand factors that influence acceptability of such measures. We aimed to study to what extent policy acceptability of car-reduction policies is related to personal norms to do the “right thing” and perceived costs associated with the policies. We hypothesized, in line with the A-B-C model, that personal norms would be more strongly related to policy acceptability when the policy was associated with moderate personal costs, rather than with very low or high costs. Such a finding would be somewhat contrary to the low-cost hypothesis, which predicts a simple linear relationship between costs and personal norm, such that personal norms become better predictors of acceptability as costs decrease. We tested this hypothesis in two ways, using data from 6045 people from seven European countries. First, we hypothesised and found that personal norms were less predictive of the acceptability of a pull measure involving few external costs (improved provision of public transport) than of a push measure involving a higher degree of cost (increased car-use taxes), across all countries. Second, we hypothesised and found that, overall, personal norms were more predictive of acceptability of the push measure when respondents felt more able to reduce their car use, and thus when the push measure would be associated with lower personal costs. This result was stronger for some countries than for others. We discuss implications for policy.