Six strategies have been used to reduce the amount of pollutant emissions coming from on-road motor vehicles: (1) reducing the emissions from new vehicles that displace older, high-emitting vehicles; (2) accelerating vehicle fleet turnover to get new vehicles into the fleet more quickly; (3) reducing emissions from in-use vehicles through such strategies as vehicle inspection and maintenance strategies; (4) reducing travel demand to reduce vehicle activity; (5) improving traffic flow to reduce emission rates; and (6) use of low-polluting, alternative fuels