Homepage > ... > Public Works > Signal Operations & Maintenance > Traffic Signal EquipmentE-mail storyPrint friendly format
Traffic Signal Equipment

Traffic signals are more costly than is commonly realized, even though they represent a sound public investment when justified. The major components associated with the installation of a traffic signal are as follows:

    • A Traffic Signal Controller¬†
    • Signal Heads
    • Vehicle Detectors
    • Signal Poles and Supports
    • Signal Design and Engineering








The controller is the signal's brain. It consists of electrical or computer controls that operate the selection and timing of traffic movements in accordance with the varying demands of traffic as registered with the controller unit by detectors.

Signal faces are part of a signal head provided for controlling traffic in a single direction and consisting of one or more signal sections. These usually include solid red, yellow and green lights and, at times, include red, yellow and green turn arrow lights as well. The signal head can contain one or more signal faces.

Detectors are devices for indicating the passage or presence of vehicles. In Irvine, these devices consist of wire loops placed in the pavement at intersections which are activated by the change of electrical inductance caused by a vehicle passing over, or standing over the wire loop.

Contractors and inspectors can find the Traffic Signal Standards here.

Special Signal Functions

Flashing Red
According to the California Vehicle Code, when a red lens is illuminated with rapid intermittent red flashes, a driver shall stop before entering the crosswalk on the near side of the intersection. The driver may proceed, subject to the rules applicable to making a stop at a four-way stop controlled intersection.

Flashing Yellow
When a yellow lens is illuminated with rapid intermittent yellow flashes, a driver may proceed with caution through the intersection or past the signal.

Dark Signals
When a traffic signal has gone dark, due to power failure, it is considered to function the same way as a four-way controlled intersection. A driver must stop before entering the intersection.

The City is committed to providing the safest, most efficient and advanced Traffic Signal System available. If you have any community traffic concerns, questions, or suggestions, please call the Irvine Traffic Research and Control Center (ITRAC)
at (949) 724-7324.