Traffic control signals that are properly located, operated and maintained may have one or more of the following advantages:
Signals may provide for the orderly movement of traffic by assigning right-of-way to conflicting movements of traffic.
Signals may increase the traffic-handling capacity of an intersection by permitting conflicting streams of traffic to share the same intersection.
Signals may reduce the frequency of certain types of accidents, especially right-angle (broadside) collisions.
Signals may provide for continuous movement and progression of traffic through coordination with surrounding traffic signals.
Signals may interrupt heavy traffic to allow both vehicular and pedestrian traffic to cross.
Traffic Control Signal Disadvantages
Traffic control signals may have one or more of the following disadvantages:
Signals may increase delay – both overall intersection delay and/or specific movement delay.
Signals may encourage the use of alternate and/or less adequate routes by drivers wishing to avoid the signal.
Signals may encourage increased volumes of traffic on the minor street by drivers wishing to use the signal.
Signals may encourage disobedience and disregard of traffic control devices. (During periods of lesser volume on the main street, drivers on the minor street may have sufficient gaps to cross and/or enter traffic, but be prohibited from doing so by the signal.)
Signals may cause an increase in the frequency of certain types of accidents, especially rear-end collisions.
Signal can decrease the vehicle-carrying capacity of the roadways on which they are placed.