Transportation is one of the largest and fastest-growing sources of greenhouse gas (GHG) in the country. Transportation and environmental agencies at all levels are looking for ways to reduce GHG emissions, and lessen the health and environmental impacts associated with transportation-related emissions. Urban areas provide the greatest opportunity for reducing GHG as well as other air pollutants through the adoption of specific policies and strategies to improve travel efficiency by reducing congestion and growth in vehicle miles traveled (VMT). The result is more efficient access to goods and services along with improved health and overall quality of life. Travel efficiency strategies such as commuter programs, land use changes, transit improvements, increased parking charges, road pricing, and others have been shown to reduce VMT and travel in congested conditions, and correspondingly reduce air pollutant emissions. As states and regions look for additional ways to reduce emissions, travel efficiency strategies are becoming increasingly attractive because they are often less costly to implement, can have both short and long term impacts, and can create more sustainable and livable communities when compared to the construction of additional miles of new roadway. Although many areas have embraced such strategies for a variety of reasons, there is increasing interest in considering whether a comprehensive combination of these strategies can substantially contribute to reductions in transportation-related emissions.