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Paris applied a bold (and controversial) tweak: it reduced the speed limit on its ring road to 50 km/h and added a carpool lane. One year later, studies suggest the move is working—traffic, air pollution, and noise are down.
Airparif, the regional air-quality agency, found a 6 % drop in nitrogen dioxide (NO₂) in nearby zones, and an overall 4 % decrease in traffic since 2023. But particulate matter (PM) levels didn’t budge much. The gains seem uneven.
On the mobility side, the Paris Urban Planning Workshop (APUR) reported a 14 % reduction in time wasted in jams, and a 2.7 dB noise reduction—small but audible at scale. Carpooling also grew, with fewer solo‐driver trips.
Not everyone’s sold. Regional leadership critiqued the policy, arguing that delays from slower travel might offset environmental gains. They also questioned whether noise improvements were meaningful. But municipal leaders stand by the experiment, and some propose adding sound‐absorbing pavement.