If green means go, red means stop and yellow means proceed with caution, what does a blinking yellow arrow mean?
South Dakota drivers, including those in the Black Hills, are being asked to figure that out as the state moves forward with a plan to install more flashing yellow arrows on intersection signal poles around the region.
The flashing yellow arrows replace the green "go" balls that stay lit after a green turn arrow shuts off to indicate that oncoming traffic also has a solid green light.
Department of Transportation officials say the blinking yellow turn arrows tell drivers a left turn is now permitted but serve as a reminder they must yield to oncoming traffic and pedestrians before turning left.
When the yellow arrow stops blinking and stays lit, motorists should then prepare to stop or complete the left turn if they are already in the intersection because the stoplight will soon turn red, said John Matthesen, a traffic engineer for the South Dakota DOT.
The arrows reflect a growing trend in traffic safety, Matthesen said. A national study conducted by the Federal Highway Administration found that yellow signals help reduce left-turn crashes by 35 percent, likely because drivers now see a yellow light rather than a round green light when approaching an intersection where they intend to turn left.
And yet the new flashing yellow arrows already in place locally are getting mixed reviews from drivers.
For some, the flashing yellow arrows create a moment of confusion and hesitancy.
"I think they're confusing during rush hour," said Sheila LaDeaux, an assistant manager at Arby's near the intersection of Fifth Street and Catron Boulevard ,where the flashing yellow arrow is in place. "There doesn't seem to be any sequence to when the flashing yellow arrows activate."
Rhonda Anderson, who works at the nearby Farm Service Agency, said the flashing yellow arrows appear to light at inconsistent times.
But service agency employee Stacy Smith said the flashing arrows have helped traffic flow in the intersection. Smith, a program technician at the agency on Stumer Road, said crossing at Fifth and Catron has always been tricky but has been helped by the new lights.
"It means I can proceed with caution," Smith said of Stumer Road, which takes motorists to the new Walmart super center. "I think they keep traffic flowing better."
Smith's co-worker, Jane Jensen, is also a fan of the flashing yellow arrows. "I like it," she said. "I don't have any problems."
Matthesen estimates the favorable reviews outweigh the complaints about 10 to 1, which is a good sign since more of the flashing arrows will be added to traffic signals in the coming years.
"I get some calls from people who don't like them and more calls from people who do," Matthesen said.
Matthesen wanted to assure drivers that the yellow arrows are responsive to traffic patterns.
South Dakota officials started installing the flashing yellow arrows on traffic lights about two years ago, he said.
Spearfish and Belle Fourche were among the first to receive the flashing yellow arrows, he said. In addition to the Catron and Fifth intersection, the new signals were added to lights at Peaceful Pines Road in Black Hawk. Flashing arrows will be added to two signals on Jackson Boulevard in Rapid City this summer.
Belle Fourche Police Chief Rob Hansen had his doubts when the flashing arrows appeared when Fifth Street was rebuilt through downtown Belle Fourche, but drivers quickly adapted.
"I was concerned when the state first put them in," Hansen said. "Whenever there's a change in traffic control signals it creates some uncertainty, but these seem to keep traffic running smoothly. We've had no accidents, which surprised me."