Construction begins on all-new ‘diverging diamond’ interchange in Lacey

LACEY, Wash. — One of the biggest road construction projects in Thurston County is under way.

The state is building what’s called a diverging diamond interchange at the Marvin Road I-5 overpass in Lacey.

It will be the first interchange of its kind in Washington and the Washington State Department of Transportation says it’s designed to reduce the number of crashes and ease congestion.

A video from the Washington State Department of Transportation’s YouTube channel shows what the new flow of traffic will soon look like.

Currently, drivers cross the overpass at Marvin Road and I-5 on the right side.

The new interchange will move drivers so they cross the overpass on the left side of the road, allowing those in the far left lane to have a free turn onto the interstate without stopping.

“It's really intuitive to drive through a diverging diamond interchange. You do what you always do while driving. You follow the signs, follow the striping on the road and follow the curvature of the median,” said Kim Mueller with WSDOT.

Construction is expected to happen mostly at night, so the impact will be minimal to drivers. The project is expected to be complete by 2020.

The new interchange comes as the City of Lacey projects more than 20,000 people and hundreds of new jobs will be coming into the area through 2035.

Cox Media Group