State Innovations to Reduce Vehicle Emissions

Vehicles and fuels have become much cleaner since the 1970 passage of the Clean Air Act, but the trends of increased driving and ever-worsening congestion could threaten continued air quality improvements. States are responsible for designing strategies that achieve and maintain national air quality standards, as established by the U.S. Environmental Protection Agency (EPA) for the mobile-source pollutants: carbon monoxide, nitrogen oxides, volatile organic carbons, and particulate matter.

Federal regulations largely control fuel formulas and vehicle emissions standards, but states have a wide range of other options for controlling mobile source pollution. State programs to curb pollution from motor vehicles can be grouped into the following four general categories:

• ensuring tailpipe emissions standards are met through inspection and maintenance;
• slowing the increase in vehicle miles traveled;
• mitigating congestion; and
• encouraging the purchase of alternative fuel vehicles.

This report examines a selection of innovative strategies in each of these four categories and discusses how these strategies might be applied to maximize the potential for emissions reduction.