The Manual on Uniform Traffic Control Devices for Streets and Highways is a document issued by the Federal Highway Administration (FHWA) of the United States Department of Transportation (USDOT) to specify the standards by which traffic signs, road surface markings, and signals are designed, installed, and used. In the United States, all traffic control devices must legally conform to these standards. The manual is used by state and local agencies as well as private construction firms to ensure that the traffic control devices they use conform to the national standard. While some state agencies have developed their own sets of standards, including their own MUTCDs, these must substantially conform to the federal MUTCD.
Warning signs introduced in the 1971 edition, combining both symbols and words
An example of state-by-state variations: California (foreground) paints a black line to help drivers see a double yellow line demarcating opposing traffic, while Nevada (background) does not
The Convention on Road Signs and Signals, commonly known as the Vienna Convention on Road Signs and Signals, is a multilateral treaty to standardize the signing system for road traffic in use internationally.
