Nighttime Closures and Temporary Signal Installation Coming to I-90/SR 18 Interchange Area April 14–18

Beginning Monday night, April 14, drivers near the I-90/SR 18 interchange south of Snoqualmie should expect a series of nighttime lane closures and traffic pattern changes as construction progresses on the new diverging diamond interch

Lane Closures: April 14–18
To accommodate barrier work, striping, and sign installation, the Washington State Department of Transportation (WSDOT) and contractor crews will reduce both SR 18 and I-90 to single lanes at various times throughout the week:

• SR 18 alternating traffic (Snoqualmie Parkway to I-90):
  Nightly from 9 p.m. to 5 a.m., Monday, April 14, through Friday morning, April 18, flaggers, pilot cars, and police will direct one-lane alternating traffic between Raging River and I-90.
• Eastbound I-90 lane closures near SR 18 interchange:
  • Monday, April 14, 9 p.m. – Tuesday, April 15, 3 a.m.: Double left-lane closure.
  • Tuesday, April 15, 8 p.m. – Wednesday, April 16, 5 a.m.: Single right-lane closure.
  • Thursday, April 17, 8 p.m. – Friday, April 18, 6 a.m.: Eastbound I-90 off-ramp right-lane closure.

When this work wraps up by Friday morning, SR 18 will be shifted slightly west from beneath the I-90 overpasses to near Southeast 104th Street, allowing a safe work zone for construction on the southern half of the interchange. Work is weather-dependent and subject to change.

New Temporary Signal at Southeast 104th Street
Crews will also begin installing a temporary traffic signal at SR 18 and Southeast 104th Street starting at 8 p.m. on Monday, April 14. Work will continue overnight, with pilot cars and flaggers directing traffic until 5 a.m. Tuesday, April 15.

The recently realigned eastbound SR 18 on-ramp to eastbound I-90 will close at 8 p.m. Monday to accommodate installation work. Drivers should continue north to the permanent signal near I-90 to access the eastbound freeway.

Once operational early Tuesday, April 15, the temporary signal will:

• Restore direct access to SR 18 from Southeast 104th Street.
• Remain in place through the duration of interchange construction.
• Prohibit turns red.
• Require drivers turning left from westbound SR 18 into Southeast 104th Street to yield to oncoming traffic, even on green.

Drivers Should:

• Expect nighttime delays.
• Observe the posted 30 mph work zone speed limit.
• Watch for turning vehicles and avoid blocking intersections.
• Remain alert for changing traffic patterns.

For updates, visit WSDOT’s website or follow project alerts via the WSDOT app and email notifications.