In deciding if a traffic signal will be an asset instead of a liability, Traffic Engineers evaluate nationally accepted warrants for traffic signals, both part of the State of California Traffic Manual and the Federal Manual on Uniform Traffic Control Devices. The installation of a traffic signal should be considered if one or more of the warrants in the referenced manuals are met including:
Minimum Vehicular Volumes
Is the volume of vehicles entering an intersection creating confusion or congestion?
Interruption of Continuous Traffic
Is the vehicle volume on the main street so heavy that drivers on the side street will try to cross when it is not safe?
Minimum Pedestrian Volume
Is the number of pedestrians trying to cross a busy main street creating confusion, congestion or hazardous conditions?
Does the number of school children crossing a street require special control for their protection? If so, is a traffic signal the best solution?
Will the installation of a traffic signal allow for continuous, uniform traffic flow with a minimum number of vehicle stops?
Does the intersection's accident history indicate that a traffic signal will reduce the possibility of a collision?
Will the installation of the traffic signal negatively impact the traffic flow on the existing network?
Peak Hour Delay Warrant
Is the traffic conditions at the intersection during the peak hour causing the minor street traffic to suffer undue delays in entering or crossing the major street?
Peak Hour Volume Warrant
Is the vehicle volume during the peak hour at a level that the minor street traffic suffers undue delays in entering or crossing the major street?
The decision to install a traffic signal should not be based solely upon the warrants, since the installation of a traffic signal may increase certain types of collisions, and increase delays to pedestrians, bicyclists and drivers who use the intersection.