Disadvantages of traffic signal control

According to the Ohio State Department of Transportation, traffic light can "significantly increase" the number or rear-end collisions in cars stopping at the intersection. Rear-end collisions occur when one car stops and the vehicle behind him does not, colliding into the stopped car. The traffic signal works correctly for the car that actually stopped at the intersection. However, the second car either fails to recognize the stopped car at the intersection or fails to stop at an appropriate distance to avoid collision.

The traffic lights ensure that vehicles from every direction get a chance to proceed through the intersection in an orderly fashion. Before the traffic light, however, there was one street (out of the two that make up the intersection) that dominated. After traffic lights are installed, the dominant street shares equal time with its cross street. This leads to congestion on one street during hours of heavy traffic, making traffic delays another disadvantage of traffic lights.

To avoid congestion, drivers will use alternative routes, usually residential streets. This is another disadvantage of traffic lights, according to the Ohio Department of Transportation. As drivers cut through the residential areas to avoid the congested stoplight, the congestion on those streets increase, especially in intersections that are regulated by a yield sign or two-way stop (stop signs on the inbound and outbound lanes of only one street in the intersection). The overload causes premature wear on the streets as well as an inconvenience for residents of the area.

Frustration with the traffic lights is already high during the hours of heavy congestion. A malfunctioning traffic light or one that tends to stick on red for a few seconds longer than usual only inflames the driver. The result is an increase in accidents from cars moving when the traffic light signals them to stop.