TRAFFIC SIGNAL SYNCHRONIZATION

What is Traffic Signal Synchronization?

Traffic Signal Synchronization is a method of timing groups of traffic signals along an arterial street to provide for smooth movement of traffic with minimal stops, thereby reducing delays which result in a better flow of traffic and minimizes gas consumption and pollutant emissions experienced by motorists.

Traffic Signal Synchronization in Lake Forest

Traffic Signal Synchronization Project - Phase 1 (Complete)

Phase 1 of the City's Traffic Signal Synchronization project (TSSP) replaced 62 outdated traffic signal controllers and upgraded software for an additional 20 signal controllers. The project was completed in April 2010.

Traffic Signal Synchronization Project (TSSP) - Phase 2 (Complete)

Phase 2 of the City's TSSP project re-timed 73 intersections throughout the City, as well as established corridor synchronized timing plans for major arteries. The traffic signal timing plans were developed with the help of traffic data that was collected at signalized intersections. Data collection for the traffic signal re-timing report was completed and new timings were implemented. The project was completed in October 2012.

Review the 2013-2015 Traffic Improvement Projects Brochure (PDF) for more information.

 Why is Traffic Signal Synchronization Needed?

The goal of synchronization is to get the greatest number of vehicles through the intersection with the fewest stops. It would be ideal if every vehicle entering the system could proceed through the intersection without stopping. This is not possible even in a well-spaced, well-designed system.

Therefore, in developing signal timing for traffic coordination, generally, "the majority rules" and the busiest traffic movements are given priority. Depending on a route, when the system is in coordination, the master cycle length of an arterial is generally between 60 to 140 seconds. This means that if you were entering an arterial roadway a side street, and you just missed the light, it is possible to wait between 60 and 140 seconds before receiving another green light. Typically, the busier the arterial, the longer the required cycle length.

Many drivers ask why they have to wait so long for a signal to change. Many of these drivers are waiting to enter a major arterial street from a side street. This is even more frustrating when no traffic can be seen on the arterial. To allow the coordination of the arterial, the side street must wait until the main traffic movement on the arterial has gone through the intersection. It is possible that the arterial traffic can't be seen immediately, but will soon be passing through the intersection.

How does Traffic Signal Synchronization Work?

The way traffic signal synchronization works is by calculating the arrival time for a group of vehicles at each intersection traveling at a specified speed, and then the traffic signals are strategically timed to turn green just as the group of vehicles arrive at each intersection. In order for the traffic signals to be synchronized, a group of signals must all be set to run on the same cycle length (the amount of time it takes for the signal to go from green to yellow to red, and back to green again), after the cross street has been serviced.

Where does the City Implement Traffic Signal Synchronization?

While traffic signal synchronization improves traffic flows, its benefits are more pronounced under certain conditions. Not all City streets warrant coordination. Typically, a street is selected for synchronization if it carries a higher amount of traffic along the arterial during peak hours. At this time, signals are interconnected and actively synchronized on the following segments of streets generally on weekdays, 6:45 a.m. - 9:00 a.m. and 3:45 p.m. - 6:00 p.m.:

• Lake Forest Drive - Portola Parkway to I-5

• Trabuco Road - Paseo Sombra to Cherry Avenue

• Bake Parkway - Portola to I-5 working in conjunction with the City of Irvine

• Portola Parkway - Alton Parkway to SR 241

• El Toro Road - Trabuco Road to I-5 (coordinated from 6 a.m. - 7 p.m.)

Other signals in the City operate on a first-come-first-served, or traffic activated basis outside of these hours. The following tables note the benefits of the City's Phase 2 Traffic Signal Synchronization Project, completed in 2012.

Reduction in Travel Times

Reduction in Number of Stops

Multi-Jurisdictional Signal Synchronization Projects

The City is working with the Orange County Transportation Authority, as well as the cities of Irvine, Mission Viejo, Laguna Hills, and Rancho Santa Margarita on eight signal synchronization projects across multi-jurisdictional boundaries. The projects will promote traffic circulation throughout the region and include the following corridors:

• Alton Parkway

• Bake Parkway

• Barranca Parkway/Muirlands Boulevard

• Jeronimo Road

• Lake Forest Drive

• Los Alisos Boulevard

• Santa Margarita Parkway

• Trabuco Road

The Lake Forest Drive, Los Alisos Boulevard and Santa Margarita Parkway projects were completed in 2014. The Jeronimo Road and Trabuco Road projects were competed in 2015. The three remaining projects on Alton Parkway, Bake Parkway, and Barranca Parkway/Muirlands Boulevard are currently under construction and scheduled to be completed by mid 2016

The three remaining projects include equipment upgrades to improve operations at individual intersections, and to connect the remaining traffic signals on the corridors to Centracs, the City's central traffic management system, for monitoring and operations. Updated timing plans are being developed and will be implemented once all the equipment upgrades are complete. All of the synchronization projects in the City will be monitored by the consultants, and any necessary adjustments will be made to the signal timing for a period of two years after the initial timing is implemented.