With only current methods of urban transportation available, we are mired in traffic jams. We have no choice but to breathe foul air.  We worry about civilization’s influence on the climate.  We are captive to the price of oil.  We are concerned with the lack of equity in our society because of the large number of people who cannot or should not drive. We witness an appalling number of people killed and injured in auto accidents. We wonder about urban sprawl as energy becomes more expensive.