Driving Restrictions That Work? Quito's Pico y Placa Program

Programs to reduce tra¢ c congestion and air pollution by restricting use of motor vehicles on working days have generally not met with success given existing studies of such programs in a number of cities. We conduct the Orst study of Quito, Ecuadoris three-year-old Pico y Placa program and Ond that it has reduced ambient concentrations of carbon monoxide (CO), a pollutant primarily emitted by vehicles, by 9-11% during peak tra¢ c hours. During an extended daytime period that encompasses hours when population exposure to air pollution is likely to be highest, CO concentrations have been reduced by approximately 6%. Given that ambient concentrations of CO generally track the spatial and temporal distributions of tra¢ c, these reductions in pollution suggest similar reductions in vehicle aows.