Marking the first alteration to traffic lights in Minnesota in 40 years, drivers across the state soon will encounter a flashing yellow arrow that, when illuminated, will tell them it's OK to turn left once the oncoming traffic has passed.
"Most future signal lights in Minnesota will have the flashing yellow arrows," said Jerry Kotzenmacher, senior engineer specialist with the Minnesota Department of Transportation (MnDOT). And once state roads begin using the new signals, cities and counties will follow suit, he said.
MnDOT's first permanent flashing yellow arrows went into operation Tuesday on the north and south ends of the interchange at Interstate 94 and Hwy. 95 (Manning Avenue) in northeastern Woodbury or southeastern Lake Elmo, depending on the side of the freeway.
The location selection was purely random, more timing than anything, Kotzenmacher said. The location was in line to get new lights, and they happened to be installed after the state was cleared to start using the flashing yellow arrows.
The lights are slated to be installed by MnDOT soon on Hwy. 13 and Quentin Avenue in Savage, on Hwy. 120 (Century Avenue) near Century College in White Bear Lake. In Eagan, they'll be added on Yankee Doodle Road at the intersections of Blue Cross Road and Coachman Road. Hennepin County plans to add them at intersections in St. Louis Park and New Hope.
Based on observations in Woodbury during Friday's rush hour, the learning curve is mostly short. "That's not unusual, some are a little hesitant at first," Kotzenmacher said, but he expects most motorists to catch on quickly.
The genius of the arrow is that it is pretty self-explanatory, he said, making it a safer option. That's been proved in years of study before it was approved in December for nationwide use by the Federal Highway Administration.
In 2006, the concept was tried at the junction of Hwys. 149 and 110 in Mendota Heights. "There were no accidents attributed to that flashing yellow arrow," Kotzenmacher said.
David Noyce, an associated engineering professor at the University of Wisconsin-Madison, is a national authority on traffic safety, and his years of studying flashing yellow arrows have led to its approval. As Klotzenmacher noted, Noyce's data affirm that drivers understand the unambiguous meaning of it.
"While drivers who intend to turn left comprehend a circular green light to mean 'go,' flashing yellow arrows command driver attention and signal them to proceed with caution," Noyce found in one study.
The arrow also eliminates what traffic experts call the "yellow trap" that causes many accidents. It happens when a driver is turning left with a circular yellow light, and proceeds into oncoming traffic on the wrong assumption that opposing traffic does not have a green light.
Another study by the National Cooperative Highway Research program confirmed the flashing yellow arrows result in fewer accidents than yield-on-green signals.
The flashing arrows, whose timing will be controlled based on traffic conditions, will also help keep things moving, Kotzenmacher said. At odd hours, for example, instead of having to wait for a red turn signal to change when there's no traffic around, drivers will be able to proceed legally. "That's a big complaint we get in signal control," he said.
Jim Anderson • 612-673-7199