Have low emission zones slowed urban traffic recovery after Covid-19?

Abstract

This paper bridges the gap between the literature on the pandemic’s effects on mobility and the literature on the impact of low emission zones (LEZ). Using data for large European cities in the period 2018–2021, we examine whether LEZs may explain differences in the recovery patterns of traffic in European cities after the shock of Covid. Controlling for several city attributes, we examine whether LEZ cities are less congested before and after the pandemic in comparison to non-LEZ cities. LEZs may have been more effective in reducing congestion after the pandemic because the fleet renewal process has slowed down or, alternatively, LEZs may be a proxy of unobservable factors related with attitudes of governments and citizens toward a sustainable mobility. Our results validate the traffic-mitigating role of the LEZ after the Covid-19 pandemic, although such result only holds for the pioneering LEZ cities. Hence, the traffic-mitigating role of the LEZ after the Covid-19 pandemic seems to be related to unobservable attributes that influenced the early decision to implement a LEZ. In this regard, we also find that LEZs may have induced a change in local attributes related to sustainable mobility given that we do not find differences between LEZs decided at the local or regional level.

Keywords:

• cities
• congestion
• low emission zones
• sustainability
• traffic

Acknowledgements

We acknowledge financial support from Generalitat de Catalunya (2020PANDE00058).

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 The sample includes all cities with over 300,000 inhabitants with congestion data available. We only exclude cities with road pricing schemes, which are stricter access restriction policies that may confound the effect of LEZs and, due to the low number of such schemes, do not offer enough variability to be included as a covariate.

2 Unfortunately, data in Europe of public transit ridership are not available at the city-level. It may be the case that some local agencies provide the information on public transit ridership but collecting this information from different sources with different criteria and different time periods covered would not be feasible and probably not effective given that the number of cities with available information would be small.

3 Unfortunately, our final sample for the analysis loses 143 observations due to missing information, particularly regarding population and the motorization variables. Results without these variables are available upon reasonable request. They do not change our main conclusions with respect to the support for the hypothesis tested in this research.

4 We use a stringency index that records the strictness of lockdown policies at country level that primarily restrict the mobility and behavior of citizens. In particular, it is a composite index taking value from 0 to 100 (where 100 is the strictest) based on the average score of nine indicators related to Covid19 containment and mitigation measures. They are school closures, workplace closures, cancellation of public events, restrictions on public gatherings, closures of public transport, stay-at-home requirements, public information campaigns, restrictions on internal movements, and international travel controls.

5 Unfortunately, data of auto sales at the city level are not available.

6 The European emission standards are vehicle emission standards for pollution from the use of cars sold in the European Union. The standards are defined in a series of European Union directives staging the progressive introduction of increasingly stringent standards. The stages are typically referred to as Euro 1, Euro 2, Euro 3, Euro 4, Euro 5, Euro 6 and Euro 7.

7 Recently, France and Spain have enacted climate laws that made compulsory the implementation of LEZs in cities with more than 150,000 (in force from 2025) and 50,000 inhabitants (in force from 2023), respectively.