Traffic Signal Coordination

Traffic signal coordination is a method of timing groups of traffic signals along an arterial to provide for the smooth movement of traffic with minimal stops.

The coordination of traffic signals to facilitate smooth traffic flow (progressed movement) along a street is a proven technique. The quality of the resulting progression is a function of the spacing of the signals, the prevailing speed, and the amount of traffic coming in and out of driveways between traffic signals, the uniformity of intersection sizes, and the traffic signal cycle length. The traffic volume and the proportion of the green time given to the preferred movements are also important.

Synchronization Goals
The goal of coordination is to get the greatest number of vehicles through the system with the fewest stops in a comfortable manner.

In traffic coordination, generally, "the majority rules" and the busiest traffic movements are given priority.

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.

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

Therefore, in traffic coordination, generally, "the majority rules" and the busiest traffic movements are given priority. Depending on a route, the master cycle length of an arterial could vary from 60 to 120 seconds. This means that if you were exiting a side street, and you just missed the light, it is possible to wait between 60 and 120 seconds, or whatever is the cycle length, before receiving another green light. Generally, the busier and the bigger the intersection, the longer the required cycle length.

Coordination is active in the morning and late afternoon on weekdays.

Not all City streets warrant coordination. Typically, a street is selected for coordination if it carries a certain amount of traffic along the arterial during peak hours. In most cases, coordination is active from 6 a.m. to 7 p.m. during weekdays. The individual signals operate on a "first-come-first-served" or traffic activated basis outside of these hours.

Traffic signal coordination is a major element in the on-going effort to improve the performance of the street system and maximize traffic flow.

Traffic signal coordination is a major element in the on-going effort to improve the performance of the street system and maximize traffic flow. Concerns have been raised and it has become necessary to evaluate the efficiency of the coordination system.
At this time signals are interconnected and actively coordinated on the following segments of streets in the major direction of flow generally between 6 am to 10 a.m. and 3 p.m. to 7 p.m.:
  • Bake Parkway - Town Centre Drive to Jeronimo Road (Trabuco Road, Cromwell/Calle Entrada, Toledo Way & Jeronimo Road are Irvine-maintained)
  • El Toro Road - Muirlands Blvd. to I-5
  • Lake Forest Drive - Cañada to I-5
  • Trabuco Road - Paseo Sombra to Cherry Avenue
Management of the coordination for these segments is done on an on-going basis.
Management of the coordination for these segments is done on an on-going basis. In addition, there is planned maintenance every 6 months by the City’s contract signal technician from the County. This maintenance takes two weeks on the average for each of these segments to:
  • Analyze recent traffic counts that the system has collected
  • Drive each segment to evaluate how the traffic is flowing
  • When to adjust the individual signals to obtain maximum performance
The effort to evaluate the efficiency of the signal coordination systems shall include a number of tasks. The efficiency of The Traffic Signal Coordination is frequently evaluated.

The effort to evaluate the efficiency of the signal coordination systems shall include a number of tasks. The efficiency of The Traffic Signal Coordination is frequently evaluated.
Perform delay studies.
Perform field reviews to acquire sufficient actual delay data.
Coordinate with the County of Orange to acquire data for use in this effort.
Perform a simulation run of existing conditions using appropriate modeling.
Run an optimization of the existing conditions.
Present a report of conclusions regarding the efficiency of the systems and recommendations for improvement.