For decades, urban planners have preached mass transit as the key to economic mobility, but new studies show that improving access to cars may be the best way to help the poor. ...My hometown of Charlottesville, VA, is a great example. The 43,000-person, 10-square-mile city currently operates a $6 million bus system. Its daily ridership averages under 7,000, and runs along 10 routes. Like elsewhere, the system includes full-size buses, salaried drivers, a fancy central terminal, and a morning-through-night schedule. Also like other systems, it serves a city where most housing is suburban in st...