ABSTRACT
Americans are noted for their mobility. In fact, for the last two decades, the rate at which American households have been acquiring cars and the number of miles they have been traveling with them have increased faster than population (U.S. Department of Transportation 1999). These cars are used on over 3.9 million miles of roadway, making 378 billion trips per year totaling more than 2 trillion miles. An additional 8 billion trips are made each year in the United States using public transit (American Public Transit Association 2000). All this mobility does not come without penalty. Congestion, deteriorating air quality, sprawl, and high energy use have resulted from nearly a century of this growing mobility.
