Paris ring road: what is the outcome for lowering the speed to 50 km/h?

A measure that caused quite a stir. On October 1, Paris town hall lowered the speed limit by 20 km/h on the ring road, dropping it from 70 km/h to 50 km/h. If many actors were strongly opposed to such a provision, the objective of which was in particular to reduce carbon emissions and noise pollution, a study by the Parisian Urban Planning Workshop (Apur) published Thursday October 19 attests to the first rather conclusive results.

The study carried out by the association in charge of analyzing urban developments in Paris made it possible to establish the effects generated by the reduction in speed “for each of its sections” of the ring road with rather positive results on the target indicators: congestion, accidents, noise pollution, emissions of dioxide and fine particles.

Concerning traffic, the limitation to 50 km/h would be the cause of a reduction in the traffic jam rate of -20% between the months of October and November 2023 with the same period in 2024 and of -19% of accidents. On the other hand, the measure would probably not have made it possible to reduce the average vehicle traffic during the day, the average hourly traffic having only fallen by -2%. The speed did not really vary during the day, remaining around 34 km/h. On the contrary, night speed was reduced by 16%, going from 59.9 km/h on average to 50.6 km/h.

A reduction in nighttime speed which “thus allows a reduction in road noise of -3.1 dB”notes the study. This has in fact fallen by 4% since the measure was put in place, although “noise pollution nevertheless remains much higher than the nuisances of these urban boulevards measured in October 2024 at 65.54 dB (A) for Boulevard Poissonnière and 65.1 dB (A) for Avenue Jean Jaurès. »

As for air pollution, the authors of the study estimate that the concentration of nitrogen dioxide (NO2) – a gas considered harmful to respiratory health – has fallen by -13%. That of fine particles (PM10) also tends to decrease by -24%. Air quality “is not yet below the limit value of the European directive but it is improving”tempers the study.

Advanced since 2019, the measure has been contested on multiple occasions, even after its implementation. At the end of November, two associations – the League for the Defense of Drivers and the Federation of Angry Bikers – announced in a joint press release that they had filed several appeals with the Paris administrative court in order to have the measure annulled. The protesters then denounced a “arbitrary measure” taken by Paris town hall ” alone “.