I passed the question onto a librarian from a state dot (department of transportation). His response was :
Transportation data of that type would need to requested from a state or city transportation department specifically. The requestor should start with the state dot.
Transportation data is not yet open in many places. That is some thing we are working on.
I had talked to him earlier about the opening up of transportation data in general, and he had mentioned that each state had different rights that they tried to assert over their data. As many states have rules similar to the Freedom of Information Act, it's possible that you could go that route if you really needed to.