I often get questions from Irvine residents about traffic light synchronization. To help answer these questions, I enlisted the help of my appointee to the Irvine Transportation Commission, Ken Montgomery.
Ken knows more about these matters than just about anyone. He is a retired civil engineer with more than 40 years of experience in managing public works and trafﬁc and transportation issues. He served as Director of Public Works for three Southern California cities: Norwalk, Redondo Beach, and Laguna Niguel.
Ken retired from the City of Laguna Niguel in 2009 after 18 years as that City’s ﬁrst Director of Public Works/City Engineer.
Ken has been closely following transportation and traffic issues in Irvine for decades and has served as a member of the Irvine Transportation Commission since it was re-established in May 2017, initially as its Chair.
Here is what Ken has to say about traffic light synchronization in Irvine:
Traffic Light Synchronization in Irvine
City of Irvine Transportation Commissioner
The City of Irvine owns and operates over 370 traffic signals.
All of the city’s traffic signals on the major corridors in Irvine are already synchronized.
There are another 40 Traffic signals at freeway on and off ramps that are owned and operated by Caltrans. Those 40 signals are in the process of being upgraded so they can be coordinated with Irvine’s signals on those specific corridors.
What is Traffic Signal Coordination?
Traffic Signal Synchronization is a traffic engineering technique of matching the green light times for a series of intersections to enable the maximum number of vehicles to pass through, thereby reducing stops and delays experienced by motorists.
Synchronizing traffic signals ensures a better flow of traffic and minimizes gas consumption and pollutant emissions.
Driving on a corridor that is synchronized does not means that a driver will get all green lights. Rather, the system attempts to maximize the efficiency of the system favoring the heaviest traffic directions depending on the time of day.
For instance, Jamboree Road traffic is twice as heavy in the southbound direction in the morning compared to morning northbound traffic. The synchronization system sets the timing to favor the southbound direction in the morning. The opposite occurs in the evening peak period when north bound Jamboree traffic is much heavier than the southbound traffic.
Irvine’s Traffic System
The City operates 19 synchronized traffic signal systems that are currently not coordinated with the Caltrans signals. Within the next 12-18 months, the Caltrans signals will be coordinated with the City’s synchronization program, which will considerably help traffic flow on those corridors.
These 19 synchronized traffic signal systems crisscross each other, which means that two heavy traffic corridors are competing for the same green light time. Also, heavy left turn demand at intersections limits the amount of green light time available for through traffic. In addition, timing plans for these corridors can get out of date as traffic patterns change all the time. The city is constantly taking new traffic counts and making adjustments to the synchronization plans.
Traffic signal equipment also gets old and obsolete, so the city typically upgrades all the equipment and recalculates the timing plans on three or four corridors per year. These updates also involve adjacent cities so the synchronization program can operate across city lines. For example, we currently have two synchronization projects underway with the City of Tustin.
The City of Irvine has a traffic signal control center at City Hall, called the Irvine Traffic Research and Control Center (ITRAC) that monitors those 19 synchronized corridors with video detection. ITRAC is staffed by traffic engineers from 6:00 a.m. to 8:00 p.m. When there is a construction project or a utility repair or a traffic accident that takes out a lane, staff modifies the signal timing to prevent a major back up in the direction where the constriction is taking place. Only Irvine and Anaheim have this type of traffic signal management center in Orange County.
There are three periods during the day when these 19 corridors are synchronized, the AM peak period, the mid-day peak period and the PM peak period. The hours of operation of those three periods varies from corridor to corridor. Corridors are typically not synchronized on weekend days except when there is a special event. When a corridor is not is the synchronized mode, traffic signals operate independently within certain pre-programmed parameters. Traffic signals detect the presence of vehicles and bicycles all around the intersection and allocate the green light time as necessary.
Reporting a Problem
If you ever observe a traffic signal that you think is not functioning properly, call ITRAC and report it.
Their direct line is 949 724-7324. Just tell them what you observed at a specific traffic signal and they will check it on the monitors and fix the problem if necessary. Traffic signals are complicated systems and require constant observation.
I know we would all love to have green lights all the time, but that is just not reality. If it were, we would implement the “All Green Light Plan” — as would every city.