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A motorist prepares to turn at a flashing yellow arrow from the Beaverton-Hillsdale Highway to onto Southwest Watson Avenue in Beaverton. (Thomas Boyd/The Oregonian)
Few places in the U.S. have adopted the technology faster than Washington County. Since 2009, the county has replaced about 400 traditional signals using solid green, yellow and red lights with ones including pulsing amber left-turn arrows.
But in a new study expected to tweak how transportation planners from Minnesota to Arizona employ the devices, Portland State University and Oregon State Universityresearchers found drivers are so intent on finding a gap in approaching traffic that they often don’t even bother to check for pedestrians.
Using a simulator modeled after flashing-arrow intersections in the Portland suburbs, up to 7 percent of drivers didn’t look at all for people in the crosswalk.
“The more oncoming cars, the less attention drivers seem to pay to pedestrians,” said Chris Monsere, a PSU professor of civil and environmental engineering and co-author of the study.
That has certainly been a problem at many high-stress Washington County intersections, where automobiles almost always far outnumber people on foot and bikes.
After a noticeable jump in reported conflicts between left-turning cars and people in crosswalks, the county’s transportation planners rushed to reprogram many of the flashing arrows so that they don’t activate at the same time as “walk” signals for pedestrians.
But there’s only so much they could do for now. About 60 percent of the current controllers have first-generation technology and can’t be modified to read the new signal “logic,” the county said.
“There hasn't been any one hit or seriously hurt that I know of, but there have been plenty of close calls,” said Stephen Roberts, a county transportation spokesman. “It’s a problem we’re trying to address where we can.”
Flashing yellow arrows tell drivers stopped at an intersection that a “permissive” left turn is allowed as long as they yield to oncoming traffic, which has a green, and pedestrians.
In theory, the signals are supposed to erase gridlock at previously locked-up crossroads during rush hour, while making turning more convenient for motorists.
There’s evidence that they have eased congestion levels, idle times, pollution and safety risks among motorists across the country.
A national Federal Highway Administration study found that the flashing arrows help reduce left-turn crashes by 35 percent. Experts believe drivers who see a yellow light rather than a round green light approach turns more cautiously.
Meanwhile, Washington County says flashing yellow arrows combined with signal retiming on Murray Boulevard, Bethany Boulevard, and Evergreen Road have produced significant improvements in traffic flow, including a 35 percent reduction in commuting delays and 18 percent fewer stops at intersections.
But Monsere and David Hurwitz, an assistant professor of transportation engineering at OSU, say their analysis raises urgent questions about potential problems for vulnerable road users.
The study’s simulator drivers, all residents of Corvallis, were outfitted with “Star Wars”-styles visors that tracked the movement of their eyes at intersections with flashing yellow arrows.
“Those who did glance at pedestrians spent less time looking as automobile traffic increased, indicating a challenge to balance multiple tasks,” the researchers said. They added that drivers paid more attention to the crosswalks as the number of pedestrians increased.
As soon as Washington County officials started seeing such safety risks, they hired engineering-and-planning firm Kittelson & Associates to help it to rewrite the logic from scratch for 40 percent of its traffic controllers.
If a pedestrian activates the crosswalk signal, drivers waiting for a left turn don’t get the flashing arrow as long as the “walk” light or red "Don't Walk" are flashing. “We have a significant order for new controllers out there” at $1,500 per unit, Roberts said. “We’ll be closer to 70 percent (reprogrammed) later this year.”
Beaverton is making similar changes “where we observe it is an issue or if someone brings it to our attention,” Jabra Khasho, city traffic engineer.
Peter Koonce, Portland’s chief signal manager and a former consultant with Kittelson, acknowledged that the rush to install flashing yellow arrows started without much talk about possible conflicts with crosswalk signals.
“It’s something that became apparent fairly quickly,” Koonce said, adding that heavy pedestrian traffic in Portland has kept the city from making flashing yellow arrows more ubiquitous. The city has installed only 10 at carefully selected locations.
Monsere and Hurwitz also found little difference in driver response to signals with three lenses versus those with four. The bottom line: “The extra cost of the signals configured with four sections may not be justified,” Monsere said.
At the same time, there are drivers who wish Portland metro municipalities would invest in educating drivers more about how the flashing yellow arrows are supposed to work, possibly with signs.
“It’s a flawed system,” said Mark Porter of Tigard. “I don’t think it clicks in a lot people’s heads that the cars approaching have a green. Or they just think it’s at the end of the yellow before the red – and the speed up.”
Last month, Porter’s wife, Shari, suffered minor injuries after her sister attempted to turn left at the flashing yellow arrow from the Beaverton-Hillsdale Highway to Oregon 217. His sister-in-law didn’t know the oncoming traffic had a green, he said.
Instead of yielding, she turned into the path of an approaching car that hit her SUV, sending it rolling until it came to rest upside-down against a sign pole.
“These flashing arrows definitely improve traffic flow,” Porter said. “But I have to ask: At what price?”
-- Joseph Rose