A selective diesel vehicle ban’s impact on NO2 concentrations in Munich: a quasi-experimental study

Abstract Background The European Union’s current NO2 concentration limit of 40 μg/m³ is regularly exceeded in Munich, Germany. This limit is likely to be reduced towards the WHO recommended target of 10 μg/m³. In response, the city enacted a selective ban on older diesel vehicles, specifically those categorized as Euro 4 or older, within the current low-emission zone in February 2023. Our study examined how Munich’s selective ban on diesel vehicles impacted NO2 levels, concentrating on the six-month period after its introduction. Methods We employed a synthetic control approach in the primary analysis and a controlled interrupted time series approach in the secondary analysis. These quasi-experimental methods establish a ‘counterfactual’ no-intervention scenario, allowing for comparison with the actual observed scenario and estimation of the impact of the intervention. Historical data from monitoring stations within and outside the low-emission zone from 2014 to 2022 were utilized as controls, while potential confounders were considered. Results NO2 concentrations within Munich’s low-emission zone decreased across the study period. Effects of the selective diesel vehicle ban at monitoring stations within the low-emission zone were minimal, with wide confidence intervals indicating uncertainty. At Landshuter Allee, the average intervention effect was -2.67 μg/m3 (95%-CI = [-12.72; 7.38]), at Stachus it was -2.74 μg/m3 (95%-CI = [-9.91; 4.42]) and at Lothstrasse, it was -1.03 μg/m3 (95%-CI = [-7.75; 5.69]). The secondary analysis confirms these findings. Conclusions Munich’s selective diesel vehicle ban had limited effects in reducing NO2 concentrations. Factors such as its narrow focus on Euro 4 diesel vehicles, numerous exemptions, and unclear enforcement may explain this outcome. Comprehensive strategies and continuous monitoring and evaluation are crucial for effectively addressing urban air pollution and protecting public health. Key messages • Munich’s selective diesel vehicle ban had minimal effects on reducing NO2 levels, possibly due to its narrow scope, many exemptions, and unclear enforcement. • Current guidelines and court rulings signal the need for more effective solutions beyond selective bans, emphasizing the importance of well-designed interventions and rigorous evaluation.