Traffic Signals

How do I Report a Traffic Signal Concern?

If you wish to report a malfunctioning signal, call Public Works at (949) 461-3480 or use the City's Ask Lake Forest system. Ask Lake Forest is available 24 hours a day.

What are the Advantages of Traffic Signals?

The primary function of any traffic signal is to assign right of way to conflicting movements of traffic at an intersection. Traffic signals are not a "cure-all" for traffic problems. The primary goal is to attain the safest and most efficient overall traffic flow possible.

Here are some advantages of a traffic signal:

  • Offers maximum control at intersections and provides orderly movement of vehicles.
  • When properly timed, a traffic signal increases the traffic handling capacity of an intersection.
  • When installed under conditions that justify its use, a signal is a valuable device for improving the safety and efficiency of both pedestrian and vehicular traffic. (Unjustified traffic signals can result in additional rear-end collisions, excessive delay, disobedience of signals, and diversion of traffic to residential streets)

What Traffic Signal Equipment are Commonly Used?

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:

  •  Traffic Signal Controller - 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 Heads - Signal faces are part of a signal head provided for controlling traffic in a single direction and consisting of 1 or more signal sections. These usually include solid or arrow lights in red, yellow, and green.
  •  Vehicle Detectors - Detectors are devices for indicating the passage or presence of vehicles. The most common 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. The City also uses video detection of the presence of vehicles via cameras installed on the traffic signal mast arms. Radar detection is also being used at some newer or recently modified traffic signals.

Why Traffic Signals are Needed?

As traffic volumes increase beyond the capability of lesser controls, such as an all-way stop, it may be necessary to install a traffic signal. Before installing a traffic signal at an intersection, traffic engineers evaluate accepted warrants for traffic signals (justifications), which are found in the State of California's Manual on Uniform Traffic Control Devices (CAMUTCD).

Special Signal Functions

The transfer of a signal control to a special signal operation is called preemption. There are three common types of preemption:

  • Emergency Vehicle
  • Railroad Crossings
  • Transit Vehicle

Alternate Signal Modes

  • Flashing Red: According to the California Vehicle Code (CVC), when a red lens is illuminated with rapid intermittent red flashes, a driver shall stop before entering an intersection. The driver may proceed subject to the rules applicable to a 4-way stop controlled intersection.
  •  Flashing Yellow: When a yellow lens is illuminated with rapid intermittent yellow flashes, a driver may proceed through the intersection or past the signal only with caution.
  •  Dark Signals: When a traffic signal has gone dark, due to a power failure or for other reasons, it is considered to function the same way as a 4-way stop controlled intersection and a driver must stop before entering the intersection.

Traffic Signal Timing

Traffic signals assign the right of way to various traffic movements for different time intervals depending on traffic flow levels. Traffic signals are timed based on traffic demands at certain times of the day. Traffic signals attempt to assign most of the available green time to the heaviest traffic movement. Traffic signal controllers provide opportunities to have a variety of signal timing plans throughout the day.