A thorough analysis of traffic operations and other factors is always prudent when considering the installation of traffic or pedestrian control signals. When traffic signals are properly located and operated, they can facilitate the orderly movement of traffic, increase traffic capacity, and reduce certain types of accidents. However, the benefits must be compared with the potential disadvantages including: creating excessive delay, disobedience of the signal by motorists diversion of traffic onto adjacent roadways, and increased rear end accidents.

Signal warrants analyses often include 12-hour traffic and pedestrian counts, projections for future traffic flows, warrant comparisons, accident history reviews and evaluations of site specific issues. In some cases, the ability to progress traffic along the system is addressed with traffic flow modeling to ensure that the new installation will not disrupt the system. Design, placement, and operations are all key factors in an effective signal installation that must be considered.

The criteria outlined in the Manual on Uniform Traffic Control Devices (MUTCD), published by the Federal Highway Administration, United States Department of Transportation, is used as a guide. The MUTCD provides eight different warrants for signalization that are based on hourly traffic volumes, traffic operations, pedestrian volumes and accident experience. The Manual states that a traffic signal should not be installed unless one or more warrants are satisfied, an engineering study indicates that the installation will improve the overall safety and/or operation of the intersection, and that a traffic signal will not seriously disrupt progressive traffic flow.