Manual on Uniform Traffic Control Devices

The Manual on Uniform Traffic Control Devices for Streets and Highways (usually referred to as the Manual on Uniform Traffic Control Devices, abbreviated MUTCD) 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. Federal law requires compliance by all traffic control signs and surface markings on roads "open to public travel", including state, local, and privately owned roads (but not parking lots or gated communities).

Source: Wikipedia — Manual on Uniform Traffic Control Devices (CC BY-SA 4.0)