The impact of London traffic restrictions: Effective but insufficient

Short and long-term exposure to air pollutants has been shown to be strongly associated with mortality and morbidity. This is a particular problem in big cities, largely due to traffic. In response, low emission zones (LEZ) are becoming more common in cities all over the world. London introduced its Toxicity Charge in 2017 and the more restrictive Ultra Low Emission Zone (ULEZ) in 2019. In this paper, we evaluate the effectiveness of these policies on NO2 levels. Our results show that NO2 levels significantly dropped in the roadside stations, especially after the implementation of the ULEZ. Similarly, at the background stations, the Toxicity Charge and the ULEZ had a similar, smaller effect. Furthermore, our results suggest that there was a positive spillover effect associated with both traffic policies, which was, however limited to the area within the North and South Circular Roads. In any case, while these policies have been useful to comply with the recommended limits on NO2 levels, alleviating Londoners’ health problems, they need to be enhanced since some stations still are above those limits.