A state DOT or toll road authority's jurisdiction over sign codes is somewhat limited. They can't do all that much about signs and billboards that are erected outside of the highway's right of way. That comes down to city and county sign codes as well as zoning ordinances for commercial, residential or industrial property. Here in Oklahoma, tribal governments can have their say on things like how many billboards can be installed every so and such many feet. Just look at the parade of double-stack and 4-stack billboards next to I-44 just North of the Medicine Park exit.
Then there are recent court cases that have shot giant sized holes through many types of sign ordinances. One example, Reed v. Town of Gilbert ruled that any content-based regulation for signs was a violation of the first amendment. A town's sign code can't treat the sign of one type of business different than another category of business. Then there is the matter that on premise signs are by far one of the most important marketing tools for a brick and mortar business. Severe restrictions on what kind of sign a business can install will hurt that business.