I'm a filmmaker and I'm looking for a "road historian" for a script I'm working on. I would love to interview someone about specific and general questions about the paving of roads during the early 1900's (Specifically, the Federal Aid Road Act of 1916). If interested, I would also love for the person I interview to be a consultant so that we get much accurate for the film as possible. Feel free to comment or PM me if you are someone (or if you know someone) that could help.
You might try reaching out to Carlton Reid who wrote a book on the subject: http://www.roadswerenotbuiltforcars.com/
He's on twitter @carltonreid
It's very bicycle centric (for good reason) and a bit earlier than the 1916 act you reference so perhaps it's not a perfect fit - but might be valuable info as a prelude?
You might also try reaching out to the League of American Bicyclists https://www.bikeleague.org/ as they are the natural succession of the original organization that lobbied for paving the roads in the US.
Hope this might be of some help.