Green Waves, Traffic Signal Synchronization, and the 200 Street Corridor

A traffic signal along 200th Street.

One of the questions that I receive from residents in Langley is if the traffic signals along the 200th Street corridor can be synchronized to promote both speed limit compliance, and the efficient movement of people and goods. Some people refer to this as a “green wave.”

The go-to reference guides for me are put out by the National Association of City Transportation Officials. This organization provides transportation guides based on best-practices, and real-world examples from urban areas with a focus on North American cities. Their Urban Street Design Guide states the following about the synchronizing of traffic signals:

Coordinated signal timing is typically applied on corridors with closely spaced intersections (1/4 mile or less) [400 meters or less], and where there is evidence of a desire for “platooning”—the seamless flow of a given street user or set progression speed. Where applied, coordinated signal timing should meet the specific goals and parameters of the surrounding context.

One of the key requirements is a close spacing of traffic signals. The greater the distance between traffic signals, the less likely that traffic can stay “platooned” together. If the platoon of traffic starts to disperse, traffic signal synchronization becomes ineffective.

If you want to get into the details of this, I found a presentation called, “Arterial Traffic Analysis: Coordination of Fixed Time Traffic Signals” by Dr. Gang-Len Chang.

Based on the 400 meter or less rule-of-thumb, the only section of 200 Street that could be coordinated would be between Fraser Highway and 66th Avenue. This area contains traffic signals that are owned and operated by Langley City, the BC Ministry of Transportation, and the Township of Langley.

To synchronize this section of road, all three agencies would have to have compatible traffic signal software and hardware that could be coordinated together. This is not impossible, but would require funding and political will. The BC Ministry of Transportation would also have to be convinced to prioritize this section of 200th Street over their provincial highway. Fraser Highway and other “side streets” would not be prioritized in this section of corridor.

The biggest challenge would be the rail crossing between Logan Avenue/Production Way and the Langley Bypass. Rail traffic overrides all traffic coordination, and would be the likely fly in the ointment to signal coordination.

Traffic signal coordination makes sense in areas where there is a close spacing of traffic signals, and can be an effective tool to nudge people into keeping the speed limit. Today along 200 Street, there is one section where signal synchronized could be applied if synchronization could be maintained even with unpredictable rail traffic.