ARLINGTON — While several more weeks of landscaping still lie ahead, the concrete and lane striping on the new roundabout at the intersection of state routes 9 and 531 were all but completed by Friday, Nov. 9.

The busy SR 9/531 intersection was chosen to be converted from traffic signal-directed into a roundabout in part because of the 28 collisions resulting in 29 injuries at that intersection within a five-year span.

The Washington State Department of Transportation’s contractor, Interwest Construction, began prepping the work area starting on April 30 and commenced work in earnest during the week of May 7, when they began closing lanes at night. A series of lane closures on state Route 9 followed throughout the summer. WSDOT awarded the $5 million contract to Interwest Construction last year, after WSDOT engineers decided to convert the SR 9/531 intersection into a roundabout back in 2009.

“This roundabout is going to be a change for drivers,” WSDOT Engineering Manager Jay Drye said. “It’ll be a great safety improvement for sure. It might take a little getting used to, but once people get the hang of it, I think it will really improve traffic flow by cutting down on delays and crashes.”

WSDOT spokesman Dustin Terpening echoed Drye’s message by citing national studies showing roundabouts reduce injuries by 75 percent, fatalities by 90 percent and overall collisions by 37 percent at intersections where they replace signals.

“There’s a lot of other benefits to roundabouts as well,” Terpening said. “They cut down on traffic congestion and are better for the environment for largely the same reasons, since they eliminate the stop-and-go of traffic lights. Whether you’re idling at a red light or punching the gas pedal after the light goes green, you’re sending out more exhaust then you would be if you were able to just keep going through.”

Rather than stopping and going, roundabouts slow down all incoming cars to turn right at a relatively steady rate of speed, which Terpening deemed safer as well as more convenient.

“It’s much smoother,” Terpening said. “With a red light at night, you have to stop even if there’s no one else there, but with a roundabout, you just turn on through. It also eliminates the risk of high-speed rear-end and T-bone collisions, which produce the greatest numbers of injuries and fatalities.”

According to Terpening, Interwest Construction and its 18 subcontractors are projected to hold the line on the project’s $5 million budget, and the roundabout itself is expected to serve an estimated 16,000 drivers per day. Given the number of semi-trucks and horse trailers that use state routes 9 and 531, WSDOT built the roundabout to accommodate larger vehicles.

Washington state ranks second in the nation for the most roundabouts. There are approximately 240 roundabouts across the state and roughly 70 of those are on state highways. Only Colorado has more roundabouts.

For more information, log onto www.wsdot.wa.gov/projects/search and www.wsdot.wa.gov/safety/roundabouts.