Summary

---

The shape and prosperity of modern life depend heavily on extensive and efficient transportation. In the United States, transportation’s scope and scale are truly enormous. So too are its consequences for personal mobility, urban form, employment, economic efficiency, public health, the environment, and dependence on foreign sources of petroleum. Although many aspects of transportation are handled through the private sector, the public role in economic, safety, and environmental regulation and the provision of infrastructure and transportation services is broad and complex. Many of the most controversial policy choices at the national, state, and local levels depend heavily on technical analyses of the consequences of current or changed policies. The Transportation Research Board of The National Academies contributes to the resolution of these issues by convening and facilitating the work of balanced committees of experts who provide dedicated service, without financial compensation, in the public interest.