A new interchange at 116th Street NE and I-5 is entering its fourth and final phase of construction. Some ramp and lane closures in the southbound and northbound lanes are expected to occur overnight starting this week.

This is a $62 million project led by the Tulalip Tribes, in cooperation with the Washington State Department of Transportation, as well as the Federal Highway Administration, U.S. Bureau of Indian Affairs, Snohomish County and Marysville.

Construction began in 2015 and has proceeded since then in phases.

For this final phase, the existing diamond ramps will be realigned into a “single-point urban interchange,” a configuration that allows more drivers to turn in a single cycle by using one signal to control all crossing traffic. Along with the traffic signal, new lighting will be added. Crews also will do stormwater and landscaping work, lay down pavement markings, add signage and improve water and sewer infrastructure.

The new overpass will accommodate six lanes of traffic, plus space for pedestrians and bicycles, and is expected to reduce gridlock at a location where 25,000 vehicles per day get off the freeway — one-quarter of all traffic that travels that stretch of I-5.

When all is said and done, project planners expect to see accidents cut in half and rush-hour delays reduced to under 1 minute by 2042. Rush-hour delays now are in the 10-minute range.

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