Traffic signals help motorists take turns at an intersection, which engineers call providing right-of-way. Traffic Signals are used when other control methods, such as stop signs, do not work. A traffic signal is sometimes the best solution when cars stack up on a side street, while waiting for a gap in main street traffic.
Traffic signals are also helpful at times when a high volume of accidents occur at an intersection caused by incorrect assignment of right-of-way by drivers. These accidents typically involve two or more cars, each from the main street and side street, colliding at right angles. The cause of these accidents can also be contributed to inadequate visibility or sight distance at an intersection. As a result, some accidents cannot be remedied with traffic signals. For that reason, traffic engineers carefully consider the types of accidents that occur at an intersection when choosing the most appropriate traffic control device.