How does a traffic signal know if a car is present?

There is a wire in the pavement behind the crosswalk called a loop detector. The wire creates an electrical field in the air above the pavement. When a large object interrupts the electric field, the signal knows that a vehicle is present and will provide a green light at the proper time in the established traffic signal cycle. During peak travel times, the wait will be a maximum of two minutes. During non-peak travel times, the wait is a maximum of 90 seconds.

Some people think that if they back up and drive forward again, they will make the signal change quicker. This does not work. The mechanism does not count the number of vehicles waiting.

At some locations, motorcycles or "high-rider" vehicles will not be able to interrupt the electrical field. If this occurs, please note the street, the intersection, the lane, and the time of day and report this to the Traffic Engineering Division. Some people feel that if they get out of their car and push the pedestrian button, they will get the green light quicker. They will not. The pedestrian push-button does not make the green light come on sooner. It does make the green light longer. It takes longer for a person to walk across a street than it takes for a car to drive across a street.

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1. May I have a "children at play" sign on my street?
2. May I have a speed limit sign on my street?
3. How does a traffic signal know if a car is present?