One hundred years ago, the United States had a public transportation system that was the envy of the world. Today, outside a few major urban centers, it is barely on life support. Even in New York City, subway ridership is well below its 1946 peak. Annual per capita transit trips in the US plummeted from 115.8 in 1950 to 36.1 in 1970, where they have roughly remained since, even as population has grown. This has not happened in much of the rest of the world. While a decline in transit use in the face of fierce competition from the private...