What about people who work for a living making service calls who can make twice as many because they don't sit in traffic as long? What about poor people who may choose to carpool to save money but who get an extra hour of leisure time each day to spend with their kids?

Meanwhile, if slightly wealthier people end up riding the subway, that will help a bit with public safety -- I lived in NYC a few years ago and never felt remotely in danger on the subway any time of day or night.