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Diverging Diamond interchange is making progress in Lacey


A lot of drivers are going to get their first look at the state’s newest interchange as they drive around for Memorial Day. This diverging diamond feature is the first of its kind in Washington state.

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If you haven’t traveled between Tacoma and Olympia lately, you will notice a big change around Lacey. Work has been underway for two months on the new interchange at Marvin Road. The Washington State Department of Transportation has moved a lot of dirt and the area looks quite a bit different.

WSDOT has also started paving a new frontage road that runs along the freeway in the southbound direction. I drove through this spot last weekend and it really feels a lot wider with that lane to your right, even though it’s not part of the freeway. I-5 has a different feel and is, visually, much different.

As for the project itself, work is on hold for the Memorial Day weekend, but a major change is coming next week.

“We’ve reached a point in the construction where we have to work where people normally drive,” said Doug Adamson with the Washington Department of Transportation.

The Marvin Road overpass will be closed from Friday night, May 31, to Monday morning, June 3. The off-ramps to Marvin Road will also be closed, but when they re-open, the detour that drivers have been using on southbound I-5 to Marvin Road will be gone.

“All traffic comes off the southbound exit to Marvin Road has been detoured up and around local streets to come back onto southbound Marvin Road, while we essentially rebuild one quadrant of the overpass,” Adamson said.

The Marvin Road detour has been in place since mid-April. Drivers will once again be able to turn left at the light, over I-5 to the shopping area.

This is the first diverging diamond interchange under construction in the state. There are plans to build one where Highway 18 meets I-90 in Snoqualmie and another where the extension of Highway 167 crosses I-5 in Fife, which is part of the Gateway Project.

If you don’t know what a diverging diamond is, be sure to check out the video here.

The simple explanation is that you drive on the opposite side of the road than you are used to when you go over the freeway. Follow the signs. This allows you to make a direct left turn onto freeway on-ramps without having to worry about cross or on-coming traffic.

The layout reduces crashes and congestion. It’s a little weird your first time, but it will make sense after you try it.

The interchange is expected to open in 2020.

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