I-90 and Highway 18 Interchange Nears Completion With Weekend Closures Ahead
Favour Bitrus
March 30, 2026
A major reconstruction of the interchange at Interstate 90 and State Route 18 is entering its final phase, with drivers warned to expect at least three extended weekend closures as crews complete paving and striping work on the new diverging diamond interchange.
The Washington State Department of Transportation says traffic control setup begins the night of Tuesday, 31 March, with paving work starting Thursday, 2 April at 9 p.m. At least one lane of SR 18 is expected to reopen by 5 a.m. on Monday, 6 April. Dates for the two subsequent weekend closures have not yet been announced, but WSDOT says each will follow the same pattern, beginning on a Thursday night and reopening at least partially by the following Monday morning.
The $188 million project has been years in the making and is designed to reduce congestion and improve safety at one of the region’s more consistently problematic interchanges. The diverging diamond design, which routes traffic through a crossover pattern to eliminate left-turn conflicts with oncoming vehicles, is intended to cut down on the delays that have long plagued the corridor.
The safety case for the project is substantial. Between 2008 and 2021, more than 400 crashes were recorded on SR 18 at this location, killing six people and injuring 170 others. WSDOT says the improvements are expected to make the stretch significantly safer for the tens of thousands of drivers who use it daily.
The full project is expected to wrap up by this summer.
