[occz]

That source makes claims that its data does not actually back up - that road infrastructure is actually paid for by user fees, while only actually providing data that highway infrastructure is paid for by user fees. Highways are clearly not most road infrastructure.

[cyberax]

They use the Census data reported by the cities. It's called "highway and street", and it includes all the surface roads except for roads with limited access. Their table just somewhat misleadingly removed the "street" part of the series name.