How far can we improve urban air quality and population exposure by changing mobility? An analysis in Paris

Atmospheric pollution still is a major sanitary problem in urban areas. Road traffic remains an important source of pollutant emissions, and it is strongly influenced by urban mobility. This study investigates the influence of five ambitious mobility scenarios in Paris to reduce pollutant emissions, concentrations and outdoor population exposure to regulated pollutants (NO₂, PM_2.5), and emerging ones (ultrafine particles (UFP) and black carbon (BC)), using a multi-scale modeling approach. The mobility scenarios suppose: reductions and renewal of utility vehicles fleet; reductions and renewal of passenger cars fleet; a widespread practice of home-office in Île-de-France region; an electrification of vehicle fleet; and a replacement of particular and utility vehicle fleet to soft mobility. In general, all scenarios reduced pollutant emissions, concentrations and outdoor population exposure for the analyzed pollutants, but with different levels of efficiency. Replacing particular and utility vehicles to soft mobility reduced the most UFP concentrations (up to 43%), and the electrification of vehicles led to the highest reductions for NO₂ (up to 75%). Similar reductions on BC were observed with these two scenarios (up to 50%). However, no scenario was effective to strongly reduce PM_2.5 concentrations (up to 16%), pointing out the importance to also reduce emissions from sources other than traffic in the region. Reducing/renewing particular vehicle fleet was more effective than utility vehicles to reduce pollutant concentrations. The widespread home-office practice proved a small, but non-negligible effect to reduce concentrations for NO₂ and BC, similar to those obtained by reducing/renewing utility vehicles.