The authors diagnose a lack of evidence-based arguments in the discussions about urban air pollution and highway speed limits that leads to deadlock and does not further the debate. Two aspects stand out across the board: First, discussants fail to explain how studies about the effects of political measures qualify as causal and thus reliable evidence. Secondly, the debate neglects important dimensions affected by potential interventions and thus prevents a comprehensive assessment in terms of social costs and benefi ts. They call for a more differentiated examination of causal relationships and for an encompassing evaluation of potential transport policies.