Washington state has quietly built over 600 roundabouts

Washington state has built 607 roundabouts across the state, the fourth-most in any U.S. state, reports Mike Lindblom in The Seattle Times.

"Washington’s roadway overhaul unfolded quietly, at a few crossings where highway engineers hoped they could reduce crippling crashes, if they made drivers outside Bellingham, Lake Stevens or Marysville travel in circles," Lindblom explains. "A study of 2009-16 data, by the insurance institute, found that in 540 multilane Washington state roundabout crashes (four per year per site), only 18, or 3%, resulted in injuries. Total crashes declined 9% per year on average, and injury crashes also lessened, indicating that drivers got safer with experience."

According to a broader national study by the Insurance Institute for Highway Safety, roundabouts lead to 72% fewer injuries and 35% fewer crashes. "Because drivers bend through at 15 to 20 mph, rather than zip straight through an intersection at 30 to 50 mph, severe injuries decline."

The more than 600 large roundabouts are in addition to over 1,000 smaller neighborhood traffic circles that have existed in Seattle for fifty years. Lindblom explains that roundabouts aren't effective everywhere: for example, they don't work well where traffic mostly flows in one direction, or in areas with a lot of pedestrian traffic.