"Uniformity" means treating similar situations in the same way. Applied to traffic engineering, uniformity simplifies the drivers' tasks because it aids in instant recognition and understanding. Uniformity aids police, courts and road users by giving everyone the same interpretation. It aids public-highway officials through economy in manufacturing, installing, maintaining and administering the roads.
The Manual on Uniform Traffic Control Devices is the publication that sets forth the basic principles that govern the design and usage of traffic control devices. The manual was prepared by a national committee that included state, county and municipal representation. The standards in this manual, with certain exceptions, apply to all streets and highways regardless of the government agency having jurisdiction.