15 Jul 2022

How additional actions in the road transport sector could improve air quality in Europe — an extension of the Concawe urban air quality studies (Concawe Review 31.1)

This article presents results from a modelling study carried out to examine how concentrations of the major urban pollutants (i.e. nitrogen dioxide (NO2), particulate matter (PM) and ozone (O₃)) would vary under different emission reduction scenarios, and to assess the practicability of achieving compliance with the current European Union (EU) air quality limit values (AQLVs), with road transport being the core focus of the research. The study builds on the findings of the earlier Concawe urban air quality studies which are used here as base case.

Through a scenario sensitivity analysis, the study aims to give insights into the question of what additional actions can be considered to improve compliance with AQLVs in the future — an important question from a policy point of view. A number of road transport scenarios were examined, assuming various rates (up to 100%) of substitution of diesel-powered road transport vehicles with electric-powered vehicles. Although road transport emissions were the primary focus of the study, additional scenarios were explored which examined emissions reductions from other sectors so that the contribution of road transport to improving compliance could be considered in context with other sources.

  • The major findings of the study indicate the following: All ‘beyond the base case’ road transport scenarios offer a further small and time-limited (between 2020–2025) improvement in NO2 compliance. In the longer term (post 2025), the already-legislated measures as described in the base case result in almost full compliance of NO2 with the current EU AQLVs across Europe. The impact of further NOx measures, either on road transport or on other urban emissions sources (domestic sector) will be negligible.
  • Any remaining exceedances of NO2 would require targeted, city-specific measures based on a thorough source attribution analysis, and any EU-wide and/or national reductions measures will no longer be effective.
  • Lowering the EU NO2 AQLV to align closely with the revised World Health Organization (WHO) air quality guideline value will impose significant EU-wide non-compliance issues.
  • Any additional measures to mitigate exhaust PM emissions from road transport will only offer a limited further improvement of PM2.5 compliance and only in the shorter term, while post 2025 the impact will be negligible.
  • The most effective strategy for reducing PM2.5 concentrations is related to actions concerning further emission controls or fuel substitution for solid fuel burning in the domestic sector. This will be important in addressing the significant and widespread PM2.5 non-compliance issues that will likely occur in the EU with any future move to closely align the current EU AQLV with the WHO air quality guideline value. l Ozone (O₃) compliance will not show any further improvement in any of the ‘beyond the base case’ road transport scenarios. Indeed, further reductions in NOx emissions and the accompanying loss of NO titration could eventually lead to an increase in the number of O₃ exceedance days, making compliance even more challenging.
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