In the United States, road signs are, for the most part, standardized by federal regulations, most notably in the Manual on Uniform Traffic Control Devices (MUTCD) and its companion volume the Standard Highway Signs (SHS). There are no plans for adopting the Vienna Convention on Road Signs and Signals standards.
Twenty-three states along with the District of Columbia and Puerto Rico use the manual without any alterations, 20 states have adopted it in conjunction with a supplemental volume, and seven states have a state version in substantial conformance to the MUTCD. There are also localized versions that are used in large cities such as New York City which use a naming system compatible with the MUTCD and/or state supplement. Read more