Overview
- Airparif's study published Friday, September 25, 2026 shows the Paris Centre zone à trafic limité (ZTL) and related street works contributed to an average citywide NO2 drop of about 1 µg/m3.
- Traffic fell sharply inside the ZTL, down about 18%, with smaller drops of roughly 10–12% in nearby districts and about 8% on major bypass routes.
- Local projects produced bigger gains on specific streets: boulevard Morland recorded a 40% traffic fall and NO2 declines of 2–5 µg/m3, while the Porte Maillot reconfiguration cut traffic by 29% and lowered NO2 in that sector.
- Fine particulate matter (PM2.5) showed no meaningful change after the ZTL because these particles come from many sources such as heating, industry and long‑range formation, so a single traffic measure has limited effect.
- Airparif says about 80% of the NO2 improvement is tied to road-traffic factors, with more than half of that due to fleet modernization and about 25% due to lower traffic volume, yet average exposures in Paris remain well above WHO guideline levels.