This chapter deals primarily with the function and application of traffic control signals at street intersections, and their combination into interconnected systems. For traffic control signals to achieve their operational and safety purpose, their message must be clearly understood and strictly obeyed. Of paramount importance is the requirement that signals be installed and operated in accord with proper legal authority so as to make compliance legally enforceable. Because of the need for uniformity in the meaning of various signal indications, national standards have been developed. Chief among these are the Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD), Uniform Vehicle Code, and the Model Traffic Ordinance. These documents generally outline the legislation suitable for establishing the authority for traffic signal installations, the meaning of the signal indications, and the required obedience to these displays by motorists, bicyclists, and pedestrians. State and local jurisdictions, then, must individually adopt or enact these provisions in suitable legislation or ordinances to make them legally enforceable in that jurisdiction. Engineers should be familiar with the codes and ordinances applicable to their jurisdictions in order to assure compliance.
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