As traffic volumes increase beyond the capability of lesser controls, such as a four-way stop, it may be necessary to install a traffic signal. Traffic signals offer maximum control at intersections. The primary function of any traffic signal is to assign right-of-way to conflicting movements of traffic at an intersection. This is done by permitting conflicting streams of traffic to share the same intersection by means of time separation. By alternately assigning right-of-way to various traffic movements, signals provide for the orderly movement of conflicting flows. They may interrupt extremely heavy flows to permit the crossing of minor movements that could not otherwise move safely through an intersection. When installed under conditions that justify the installation of traffic signals, they are valuable devices for improving the safety and efficiency of both pedestrians and vehicular traffic.
To install a traffic signal at an intersection, minimum criteria must be reviewed and met:
• Volume of vehicular and pedestrian traffic
• Need to provide interruption to the major flow for side street vehicles and pedestrians
• Accident history of intersection