A speed limit of 30km/h (18mph) has come into force across Paris in a drive to improve the environment, reports BBC News.
The aim is to cut accidents, and reduce noise and pollution.
A poll suggests 59% of Parisians are in favour of the measure, but some businesses are among those opposed.
Two-thirds of the city was already subject to the limit before Monday's change, which has been pushed through by Mayor Anne Hidalgo. Several key routes will remain exempt though.
These include the Champs Elysées (50km/h) and the main ring road, the Boulevard Périférique (70 km/h).
Similar limits are already in force Grenoble and Lille, as well as Bilbao in Spain, and the Belgian capital, Brussels.
The measure is being introduced now so Parisians can get used to it during a period of lighter summer holiday traffic, city officials say.