I remember a comment on HN that said the authors city analyzed license plate reader data to find out who was driving on the cities roads. 80% of the drivers were from out of town. The annoying thing about that, unlike highways much of the funding for residential and commercial roads is paid for by local taxes.

When I think about transportation I think about a paper I read about development of rail. The US and UK's experience is you run into market failure with private rail. The broad based benefits and network effects are diffuse, too many people and businesses benefit indirectly. Which means you can't charge high enough fares to pay for a optimal system.