Technology is about to trump one of the great irritations of driving: Waiting in a left turn lane for a green arrow, even as oncoming lanes of traffic show nothing but yawning emptiness.
The savior is the flashing yellow left-turn arrow, an innovation that showed up as an experiment in Minnesota in 2006 and now is sanctioned by the state and federal transportation departments.
Last month, Bloomington began adding the signals, joining Eden Prairie, Burnsville, Blaine, Woodbury, Eagan and other metro cities.
Statewide, about 100 intersections had flashing yellow turn arrows as of last week, but more are being added every day, said Kevin Schwartz, signal optimization engineer with the Minnesota Department of Transportation (MnDOT). He said that eventually the arrows will be at almost every intersection in the state. The only exception would be intersections with visibility issues.
"It's now the standard for MnDOT in the metro area," Schwartz said. "The thing to remember is that these are programmable ...
"Nobody is on the road at three in the morning, and to have folks sit there waiting [at a red turn arrow] just doesn't make sense."
Switching to the new technology is expensive, so it will likely be years before the arrows are everywhere. New signals will be phased in as old ones need replacement.
The cost per intersection can be as low as about $10,000, Schwartz said. But that varies by location. In Bloomington, the installation cost at each of the four intersections that are getting the new arrows this year is $35,000 to $45,000.
New lights were installed about three weeks ago at the intersections of American Boulevard at Southtown Drive and Bloomington Ferry Road at Old Shakopee Road. By the end of the year, they will be added to W. 81st Street at Penn and W. 82nd St. at Knox.
Kirk Roberts, Bloomington traffic and transportation engineer, said drivers seem to proceed with more caution when they see a yellow flashing turn arrow than they do with a green light that to some drivers just says "go."
"With the ones we put in so far, there's been no trouble," Roberts said. "People seem to understand it. Right now, we have supplemental signs up to explain, but I think it's pretty self-evident to most people."
Signals with the flashing yellow turn arrow are programmable, which was not always the case with old signals. Though Bloomington so far has put the new signals at intersections that have frequent gaps in oncoming traffic, the signals can be timed to activate the flashing yellow turn arrow only during certain parts of the day, such as outside of rush hour or overnight.
The new lights don't affect "walk" signals for pedestrians, Roberts said.
Signal changes are being paid for with a mix of state, county and city money, depending on the type of road involved. Installing the new lights usually takes a crew about a day and a half, he said.
"Anytime we can get people where they need to go more efficiently, quickly and safely, it's a great improvement," he said.
Mary Jane Smetanka • 612-673-7380 Twitter: @smetan