Traffic Signals

Fiber optic mapTiming & Coordination Project
Fiber Optic Network
The City of La Mesa Department of Public Works proactively improved operation of the traffic signals under its jurisdiction over the last few years. The city obtained grants from the Federal Congestion Management and Air Quality program to interconnect and coordinate the traffic signals with fiber optic cable. Currently, 53 of the 57 signals are connected to each other and to a central computer at City Hall. La Mesa has one of the most expansive traffic signal interconnect networks in the County of San Diego.

How Signal Coordination Works
Connecting the traffic signals to each other allows them to work together as a team for you, the driver. Once a traffic signal is connected to its neighboring signal and to the central computer, the two traffic signals can then be coordinated. The central computer is what coordinates the signals through constant communication by telling the signals what times of the day and days of the week to start coordination and when they should turn green in order to allow for a stream of green lights along a corridor while traveling at the speed limit. The coordination program can also increase the green light time when traffic is heaviest.

In this manner, cars progress through coordinated signals more quickly than they could through uncoordinated signals. However, when the communication between a signal or series of signals is disrupted or cut off from the central computer, or a signal is preempted by an emergency vehicle or trolley, those signals continue to operate, but they are no longer coordinated. A preempted signal will take several minutes to reorganize itself and get back into coordination.

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