Chet Skwarcan is an award-winning engineer, writer, and industry innovator in the field of traffic engineering. He is known for leveraging his creativity, logic, and technology to solve today’s engineering challenges.

Traffic Signal Coordination

If you’ve been following this column for very long, you qualify for a free t-shirt. Send me your size and $29 to cover shipping and handling (handling is expensive). Also, if you’ve been following this column for very long, you understand something about traffic growth — we can’t live with it and we can’t live without it (ask any business owner).

But, there are some “things” that can be done to relieve traffic congestion and still maintain a thriving, growing (and desirable) community.

The first thing, and the most economical thing, is to coordinate all those traffic signal things. And by that, I mean the Synchronization of Signals (SOS). The synchronization of traffic signals means traffic signals are coordinated, creating a green wave of progression throughout a roadway corridor.

Modern traffic signals have the ability to monitor changing traffic volumes and adapt signal timings accordingly. This is referred to as adaptive traffic signal control.

The progression of traffic, i.e., the green wave, can be optimized for both directions, or, in communities with heavy directional volumes, progression is optimized to favor the primary direction.

And as traffic increases (i.e., rush hour), it tends to move slower. Therefore, the green time allotted at each signal must increase to maintain progression for the primary direction. And as you can imagine, left turn arrows take their toll on traffic progression — left turn arrows bring thru traffic to a stop and therefore require careful and selective implementation — especially during rush hour.

Keep in mind that most claim their traffic signal system is coordinated. But, a truly effectivecoordinated traffic signal system requires regular data collection, optimizing of signal timings and phasings (e.g., turn arrows), vehicle detection capabilities (hardware), implementation and monitoring. Did I mention monitoring? And oh yeah, also tweaking (and monitoring).

Chet Skwarcan (traffic engineer, author, unique insights) with over 25 years of traffic engineering experience — online help available at