If there is no per-mile fare, then there is no incentive not to use the road. Using gasoline as a proxy does not charge the people using complex and expensive o

If there is no per-mile fare, then there is no incentive not to use the road. Using gasoline as a proxy does not charge the people using complex and expensive overpasses more than people using surface streets. There is no incentive to minimize construction and maintenance costs at all. No pay-as-you-go model like busses and trains have.