They may be able to reduce broadside collisions, but they cause an increase in other types of accidents, especially rear-end collissions. At an intersection that has a limited history of broadside accidents, installing a signal might reduce the safety of the intersection because of an increase in rear-end collissions. In addition, improperly timed or unjustified traffic signals can cause excessive delays, breeding frustration and disrespect by motorists for signals and other traffic control devices. Unnecessary delays nationwide lead to billions of dollars lost each year in diminished productivity and wasted fuel, while adding to the air pollution problem. The Manual on Uniform Traffic Control Devices contains 11 criteria to help determine whether the traffic situation justifies a signal.
Signals are valuable tools when used under the right conditions.
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