Coordinated Traffic Lights

Have you ever had that euphoric feeling when you breeze through a series of traffic lights all the way to your destination? The City of Gallatin is investing in a traffic light coordination system that could give drivers that sensation every day.

Gallatin’s Engineering Division is working on a plan for a traffic synchronization system that allows computerized coordination of most of the traffic lights in Gallatin from a single location. Similar systems in other cities have reduced traffic delays. Comprehensive signal retiming programs have documented benefits of 7-13% reduction in overall travel time, 15-37% reduction in delay and a 6-9% fuel savings (Institute of Transportation Engineers)

“All of these benefits stem from simply reducing the number of vehicle stops,” said City Engineer Nick Tuttle. “So while most drivers will appreciate saving time, a nice byproduct of this measure will be fewer trips to the pump and better air quality.”

Targeted Areas

The system will allow coordination of 25 traffic signals along US Highway 31E and in the downtown district from a single computer in City Hall. Eventually, the new system will be a component of the Traffic Operations Center in the Franklin House, the 100-year-old house the city acquired and moved earlier this year. “As the city grows, we are constantly looking at opportunities to improve the city’s infrastructure, but expanding the capacity of our streets is not easy, said Gallatin Mayor Paige Brown. “This innovation achieves the same result without construction delays or laying asphalt.”

How it works

To better understand how traffic signals are synchronized, picture traffic lights as a series of stopwatches, each one set at 100 to 140 seconds, which is how long it takes for the typical intersection to cycle through the green, yellow, and red lights in each direction. When one traffic light in a synchronized series turns green, the next one down the line is typically set to turn green a short time later. The next one after that is set to turn green a short time after that, and so on. The series of stopwatches is generally coordinated by one central timepiece. The lights are timed in a coordinated progression to accommodate a group of cars that traffic engineers refer to as a platoon. The idea is to keep the platoon moving in an efficient manner — limiting the amount of time those cars sit idling at red lights.