State unveils first new traffic signal in 40 yearsby Tim Nelson, Minnesota Public Radio
Lake Elmo, Minn. — There was a rare debut on the highway in Lake Elmo today. Minnesota officially turned on the state's first new traffic signal in 40 years.
It's a flashing yellow arrow, intended to make left turns safer and easier. The signal is expected to eventually blink on in traffic lights statewide.
It's a small change, but one that state traffic engineer Jerry Kotzenmacher hopes will make a big difference.
The traffic lights at the interchange of Interstate 94 and Manning Avenue now have a flashing yellow arrow facing the left turn lanes on Highway 95, about 15 minutes east of St. Paul. It signals drivers they can turn, as long as they yield to oncoming traffic.
"Traffic flows more smoothly because we can allow cars to turn on a flashing yellow arrow, rather than waiting for a green arrow," Kotzenmacher said.
That means less sitting in your car with the blinker on, looking at an empty road in front of you. It's also thought to be safer, since some dedicated left turn lanes rely on the traditional circular green light that doesn't signal traffic in the opposing lane to stop.
David Noyes, an engineering professor at the University of Wisconsin in Madison has been studying that very issue for 15 years.
"We're using the same circular green indication to tell the driver two different things, depending on whether you're turning left or going straight," he said. "As simple as that sounds, that became a very problematic issue in transportation safety. We were getting a lot of left-turn crashes -- and frankly still get an awful lot of left-turn crashes on that circular green."
Noyes may well be the nation's premiere researcher on the solution to that problem. Some states, like Michigan, solved it with a flashing red circle. In others it was a flashing yellow circle. Testing in simulators and driving labs eventually settled on the flashing yellow arrow.
MnDoT tested the change with a temporary installation in Mendota Heights in 2006. The state of Oregon has adopted it statewide and Dakota County is trying one in the city of Eagan.
But Minnesota only made the signal part of its official traffic standards recently, and the light on Manning Avenue is the state's first permanent installation of the new signal.
Noyes said drivers in tests have been able to adapt readily to the change.
"Most of the drivers were able to successfully identify that this was a cautionary, even though ... yellow by definition doesn't mean caution," he said. "It gives the driver the impression that yield is required."
And Kotzenmacher, the traffic engineer, said he thinks drivers will eventually learn to love the flashing yellow light.
"People will see it as something different, but once they understand it, they'll want it at a signal near their house," he said.
It'll take some time, though, There are about 4,000 traffic signals in Minnesota and MnDOT is the largest operator of the lights, with about 1,300 hundred of them.
The flashing yellows will be gradually adopted as traffic lights are installed and replaced, and as public works agencies can afford them.
- All Things Considered, 09/08/2010, 6:26 p.m.