Driving Restrictions That Work? Quitos 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. We conduct the …rst study of Quito, Ecuador’s three-year-old Pico y Placa program and …nd 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 ‡ows.