This was done by an order published on 8 of July of 2021 (n°2021P110904) by the City of Paris, following a public consultation about the project to generalize the speed limit to 30km/h in most of the city of Paris, compared to 50km/h previously. This public consultation was initiated by the City of Paris on 27 of October of 2020 for a period of one month, and gathered nearly 6,000 opinions in favor of this limitation. However, this speed limit will not apply to the whole of Paris: the ring road will remain limited to 70km/h, as well as certain specific roads such as the avenues of the Bois de Boulogne, the boulevards des maréchaux and others, which will remain limited to 50km/h.

This limit is primarily a road safety issue, particularly in relation to motorized vehicles, which are very present in the capital. According to some calculations, this reduction in speed would even reduce injury accidents by 25%. These reduced speeds would also allow for better "cohabitation" between road users: cars, motorbikes, bicycles, scooters, as the higher the speed, the greater the chance of accidents.

There will also be a noise aspect, as this speed limit would reduce noise pollution. But as far as nuisance is concerned, we can ask ourselves if reducing the speed of vehicles in Paris by almost 20km/h will have an impact on pollution in the city? Although one might think that driving less would reduce pollution, it seems that the opposite is true. The public institution Cerema (center for studies and expertise on risks, the environment, mobility and development) has published a controversial study on these impacts. Indeed, this study claims that a car emits 20% more CO2 emissions when driving at 30km/h than at 50km/h, and this is due to the way engines are built, driving at 30km/h would not be the optimal speed. However, it should be remembered that these figures are true when driving in a straight line, however in Paris it’s rare to have a constant speed, and in any case there is a lot of acceleration and braking, so these calculations can be nuanced. Nevertheless, this reduction in limits could encourage the use of public transport, walking and cycling, and these modes of transport would have a greater impact on pollution.

It should be noted that Paris is not the first city to experiment with these speed reductions, it’s even the ninth after Grenoble, Montpellier, Strasbourg, Nantes, Rennes, Lille, Toulouse and Bordeaux. Indeed, the city of Grenoble has already adopted this measure since 2016 and has even seen a 10% drop in traffic, as well as a reduction in road accidents.