Traffic signals should be installed when they will alleviate more problems than they will create. This determination must be based on an engineering study.
A warranted traffic signal that is properly located and operated may provide for more orderly movement of traffic and may reduce the occurrence of certain types of accidents. On the other hand, an unwarranted traffic signal can result in increased delay, congestion and accidents.
Many people seem to believe that traffic signals are the answer to all traffic problems at intersections. If this were true, no traffic engineer would deny a request for a signal. However, a traffic signal only functions by stopping traffic, and any time a motor vehicle is stopped in the road, there is the potential for an accident. It does not matter whether the stop is caused by a flat tire, a left turn into a driveway, or a traffic signal; the possibility exists that a following motorist will not notice the stopped vehicle until it is too late.
What traveler has not experienced a traffic signal suddenly turning amber a few hundred feet away? Who has not experienced waiting in a long line of cars for a traffic signal to change, moving ahead a few feet, and then having the signal turn red again? To avoid these kinds of inconveniences and the increased potential for accidents, the need for traffic signals should be based on competent engineering study.