Traffic Lights May Cut Gridlock

Mount Pleasant plans to add eight high-tech adaptive control traffic signals in an attempt to ease congestion on Highway 17.

“The plan is that once you get off the Ravenel Bridge you can drive all the way to Wando High School without stopping,” said town Councilman Elton Carrier.

The high-tech lights use computer assumptions to gauge traffic flow and patterns to adjust the lights accordingly, said Brad Morrison, the town’s director of traffic.

Already installed at intersections from Ira Road at Wando Crossing to the Isle of Palms Connector, Morrison said northbound traffic speed has increased by 35 percent and southbound traffic has gotten 14 percent faster.

Town leaders hope that once these eight lights are installed, and when Highway 17 has six lanes of capacity, motorists won’t hit standstill traffic along the bridge or at intersections inside Mount Pleasant.

“This technology evaluates the vehicle demand second-by-second — it’s always evaluating,” Morrison said. “It’s looking at each approach at the intersection and for the entire corridor.”

The technology looks at all that data — collected from cameras and through coils buried at intersections — and attempts to move entire “platoons” of vehicles along the road with no stops, Morrison said.

“Right now the signals run on fixed plans,” Morrison said. “For two-hour blocks they run the same way over and over. It can’t react if there were 300 more cars at an approach for some reason.”

The town was the first city in South Carolina to install the adaptive lights in 2010. It won an American Council of Engineering Companies traffic-engineering award for the six lights already in place, he said.

In addition to reducing wait times by up to 90 percent, the lights also reduce fuel consumption by 25 percent, according to the manufacturer’s website.

Town leaders were so impressed, they voted Wednesday to buy eight more light systems and to upgrade a handful of other “smart” lights with the latest software from Rhythm Engineering.

But the lights and their new-fangled technology aren’t cheap. The town will spend $435,000 for the lights and computer equipment that operate them.

And it will be a while before motorists notice any improvement. Construction workers must install new traffic light arms for the lights, and that won’t happen until November 2012 when the project is complete.