This number is forecast to double over the next 12 years. Transportation funding has not kept pace with demand. The ability to increase roadway capacity has shrunk. New roadways are less successful in reducing congestion. New roadways are less successful in reducing congestion, often encouraging more driving, which soon brings congestion back to pre-project levels.
Environmental concerns make expanding existing roads or building new ones difficult or impossible.
More cars have meant more noise, air and water pollution. While sound walls have mitigated noise impacts on freeways, and cleaner vehicles have improved some aspects of air quality, noise levels on other roads and pollution from particulate matter continue to worsen. Even if the money were available, environmental concerns will make new roadways harder and harder to build. Curbing the rate of growth and intensity of development in one place, however, has often meant shifting growth to other areas and increasing overall demands on a region's circulation system as well as encouraging further urban sprawl. A new model urban center, built on community-oriented planning, results in integrated land uses and a pattern of development that is efficient for transit to serve.