@enobacon The test for negligence is generally codified in state law, but there are some States that specifically point to the MUTCD for traffic or other specific reqs for traffic, e.g. PA: https://www.pacodeandbulletin.gov/Display/pacode?file=/secure/pacode/data/067/chapter205/s205.5.html. Generally, the negligence test is "what would a reasonable engineer do in the same circumstances" and that's follow the standards. I think there's a pretty long legal precedent of no liability when "we thought that was safe at the time, but now we know better."