Because of the widespread belief that traffic signals offer the solution to all intersection traffic-control and accident problems, a number of signals have been installed nationwide where no legitimate operational warrant exists. Traffic records clearly show that the attitudes and misunderstandings that sometimes lead to unjustified installations should be resisted. It is important that the selection and use of this traffic control device be preceded by a thorough study of traffic and roadway conditions and that the determination of the type of control and method of operation be based on the study data.
Traffic signals should be used only where lesser forms of control have proven ineffective because signals almost always create more "overall intersection delay." In fact, minor movements may experience excessive delay, particularly if the signal is improperly timed. As a result, many drivers switch to less desirable alternate routes or to residential streets to avoid the added delay.