Are low emission zones effective? : An event study examining Swedish municipalities

Sammanfattning

Air pollution from road traffic remains a major public health and environmental challenge in urban areas, andlow emission zones (LEZs) have become widely adopted regulatory responses. In Sweden, where municipalitieshave substantial autonomy over their implementation, the effectiveness of these zones has received limitedsystematic empirical attention. This thesis examines whether LEZs are effective by analysing three Swedishcities Umeå, Helsingborg, and Uppsala that introduced such zones recently enough to enable credible pre- andpost-implementation comparisons. Using annual data from Statistics Sweden (SCB) and the SwedishMeteorological and Hydrological Institute (SMHI), the study combines descriptive spatial analysis in ArcGISwith a staggered event study difference-in-differences design. It estimates effects on nitrogen dioxide (NO2)concentrations, privately owned cars per 1,000 inhabitants, and heavy lorry traffic relative to a comparablecontrol group. The findings are interpreted through governance, policy implementation, and urban politicsframeworks. The results show a clear and statistically significant reduction in privately owned cars per capitafollowing implementation, suggesting a durable behavioural effect. NO2 concentrations exhibit weak and lessrobust indications of decline over time, while effects on heavy lorry traffic are statistically inconclusive,however, this may be due to the level of policy implementation. Descriptive trends also reveal declining dieselvehicle shares and rapidly increasing electric vehicle adoption in the studied cities, although the causal role ofLEZs in this transition remains unclear. Overall, the evidence suggests that LEZs are most effective in shapingindividual car ownership behaviour and represent a promising but partial instrument for improving urban airquality.