Diesel bans and urban air quality: A causal study of NO2 emissions in Germany using synthetic control

Urban air pollution is a growing public health and environmental issue. This study investigates the effectiveness of diesel traffic bans in reducing nitrogen dioxide emissions in four German cities: Berlin, Darmstadt, Hamburg, and Stuttgart, from 2012 to 2022. Each city has implemented similar policies to comply with the European Union’s emission standards. Using the synthetic control method, we evaluate the effects of policies restricting diesel traffic on selected streets, street segments, and urban areas. Our results indicate that the implementation of diesel traffic bans led to significant reductions in nitrogen dioxide emissions per capita in Darmstadt and Stuttgart. However, the policy appeared to have a limited effect in Berlin and Hamburg. The study suggests that policy effectiveness is influenced by factors such as city size, pre-existing traffic patterns and the extent of diesel restrictions. In addition, our findings highlight the importance of tailoring policies to local conditions and underscore the value of using rigorous research methods when assessing the effectiveness of environmental policies.