Is there a single US Highway Code?
As others have mentioned, there is no uniform (or even close to it) driving code in the US. Some rules are foisted upon the states by the federal government (like right on red, which is now almost universally allowed except where signed otherwise, excluding a few holdout cities) through the carrot of federal highway funding. There is a document, called the Manual on Uniform Traffic Control Devices, which details requirements for signage and road markings. Some states have their own version of the manual that differ slightly or substantially from the federal document. States are generally required (by the aforementioned funding) to comply with the MUTCD. Most states through law or administrative rule require adherence to the MUTCD or their state equivalent by their highway department and cities.
