Traffic signals should be installed when they will alleviate more problems than they will create. This must be determined on the basis of 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 collisions. However, an unwarranted signal can result in creased delay, congestion, and collisions. Traffic engineers throughout the United States determine the appropriate locations for signals using standards referred to as Traffic Signal Warrants.