Get Ready for the New Diverging Diamond Interchange in Lacey

If you drive around Lacey often, you have probably noticed the construction at the Marvin Road and I-5 interchange, exit 111. You may have even felt like it’s been going on forever. Started in October 2018, the Marvin Road diverging diamond interchange may be done by the by the end of 2020, weather permitting, according to Washington State Department of Transportation (WSDOT).

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Exit 111 is a busy one, with neighborhoods, shopping, schools, parks and more in the surrounding area. Doug Adamson, communications consultant for WSDOT, shares that this is a first step in plans the City of Lacey has to develop land in Hawks Prairie. The new interchange will help ease potential new congestion as the area grows, but also help current travelers with a safer and more efficient traffic flow.

“In order to help keep travelers moving, WSDOT proposed to upgrade the existing overpass into a more efficient diverging diamond interchange,” explains Adamson. “This upgrade is also a cost-effective improvement for the growing community.”

The diverging diamond interchange, which has a $45.8 million budget, was chosen because it increases efficiency by removing conflict points, which also makes it safer “A conflict point is an area of roadway where vehicles cross, merge, or diverge,” Adamson says. “The enhanced Marvin Road interchange in Lacey will reduce the conflict points from the existing 26 to 14. This helps reduce the potential for collisions at this busy interchange.” In the new design, drivers can make a free left-hand turn onto I-5 without stopping at a traffic signal. “One of the key benefits to improve traffic flow is a free left turn onto I-5,” he continues. “Because drivers are directed to the left side of the road, there is no need to wait at a traffic signal before turning onto the highway on-ramp.”

Just last weekend, on June 26, crew closed the two ramps on Marvin Road for paving. “The vast majority of remaining work is on the overpass itself. Crews will have occasional lane and night ramp closures,” says Adamson. “While major construction like this is never easy, WSDOT is working to keep people moving during the project. WSDOT asks all users of the overpass to stay engaged via”

WSDOT does expect more closures, including total weekend closures, as they work on completing the project and asks that travelers plan ahead. On July 9, the restrictions on the southbound traffic will be lifted and the northbound left land will become a left-turn only to southbound I-5. This is a temporary change that could extend up to 24 days depending on the weather, will create congestion and delays for northbound travelers WSDOT advises. This may mean congestion and delays, but WSDOT plans to keep people moving during the remaining work, adds Adamson.

Using the New Marvin Road Interchange

Although it may look complicated, diverging interchanges have proved effective in other states across the country. “A diverging diamond interchange is intuitive,” Adamson assures. “Frequent travelers across the country likely already have used them in other states. There is nothing new to learn for a diverging diamond interchange. Travelers stop at a red traffic signal and go on green. After that, travelers follow the signs and lines.”

That doesn’t mean it can’t hurt to watch the WSDOT’s video on how the new diverging interchange will work (see below). If you want more, WSDOT has more videos on their website showing how the interchange works, including a video for pedestrians. The new interchange does feature a concrete barrier in the middle of the overpass for pedestrians and bicyclists.

Sign up for advance information about this project at

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