Paris's limited traffic zone improves air quality according to Airparif

The establishment of a limited traffic zone (ZTL) in the hypercenter of Paris at the end of 2024 has contributed to improving air quality throughout the capital, where concentrations of nitrogen dioxide have fallen slightly, according to an Airparif study published on Friday. The study shows a reduction in road traffic in inner Paris between 2023 and 2025, particularly marked within the ZTL (-18%) covering the first four arrondissements of the capital which cars are no longer authorized to cross without stopping, unless there is a valid reason. This reduction is lower in areas further from the city center, between 12% and 10%, adds Airparif.

Overall, the reduction in traffic volume was accompanied by an average drop of around 1 µg/m3 in nitrogen dioxide (NO2) concentrations throughout the capital, details the air quality monitoring association in Île-de-France. The study - the first to assess the impact of the ZTL - reveals improvements in air quality "significantly greater on certain axes directly affected by the reduction in traffic", for example Boulevard Morland (-40% traffic) in the 4th arrondissement where NO2 levels have fallen by 2 to 5 µg/m3 since the implementation of these restrictions.

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The device remains in “educational mode”

Due to a postponement of traffic, the roads located on the outskirts of the ZTL, such as boulevards Bonne-Nouvelle and Saint-Germain, recorded an increase in traffic but "which is not accompanied by a deterioration in air quality" because it is "compensated by the overall effect of the ZTL", explains Airparif. The controversial system has remained in “educational mode” since its launch in November 2024 by the City of Paris, without fining offenders. The redevelopment of Porte Maillot (north-west), carried out between 2021 and 2024, led to a drop in traffic volume of 29% compared to the previous situation, again resulting in a drop in NO2 concentrations. On the other hand, the effects of the ZTL and the redevelopment of Porte Maillot are “more limited” on particle concentrations, adds Airparif, explaining that these pollutants come “from a much broader set of emission sources” than road traffic.