Starting late Friday night, April 24, three of the Seattle region’s busiest corridors will be restricted simultaneously. Southbound I-405 through Renton, eastbound SR 18 near Issaquah, and two northbound lanes of I-5 across the Ship Canal Bridge will all be closed or reduced through the weekend.
For drivers accustomed to rerouting around one closure by jumping to another freeway, this weekend offers no easy escape. The backup routes are the bottlenecks.
A rare collision of closures across three corridors
The specifics are worth laying out clearly. Southbound I-405 between SR 169 and SR 167 closes as early as 11:59 p.m. Friday, April 24, and isn’t scheduled to reopen until 4 a.m. Monday, April 27. Eastbound SR 18, between Issaquah-Hobart Road and the I-90/SR 18 interchange, moved to a single lane earlier in the week before shifting to a full closure beginning as early as 9 p.m. Thursday, April 23, with at least one lane expected back by 5 a.m. Monday. Meanwhile, two northbound I-5 lanes across the Ship Canal Bridge remain closed for ongoing bridge repairs — a separate project already compressing traffic through Seattle.
Any one of these restrictions would reshape a weekend’s worth of travel on its own. All three at once is something different entirely. Seattle’s highway network depends on redundancy — when one route backs up, drivers shift to another. This weekend, the alternatives are already constrained before the detours even start.
What crews are racing to accomplish
The I-405 closure is tied to the Renton-to-Bellevue Widening and Express Toll Lanes project. During the window, crews will install drainage, replace concrete pavement panels, and pave the roadway — work that demands a traffic-free corridor and can’t easily be broken into smaller overnight windows.
SR 18 work is further along in its preparation. On Tuesday, April 21, one lane of eastbound SR 18 was closed to remove approximately 8,500 feet of guardrail and concrete barriers — groundwork for the full weekend paving operation tied to the I-90/SR 18 Interchange Improvements project. The full closure lets crews finish that paving without interruption.
The job doesn’t end when lanes reopen Monday morning. Reinstalling guardrail, curbing, and stormwater drains will continue in the eastbound right lane of SR 18 through Wednesday, April 30.
Where congestion will spread — and where it won’t
WSDOT is explicit about something drivers may not anticipate: the disruption won’t stay neatly inside the construction zones. When multiple major corridors tighten at once, traffic bleeds onto local roads and parallel routes that simply weren’t built to absorb freeway-level volume. Travelers may find themselves stuck on surface streets they don’t normally associate with highway construction.
One limitation is especially firm. Issaquah-Hobart Road and Issaquah city streets are not suitable for semi-trucks or freight traffic — carriers need to plan around this entirely, using a signed detour: westbound SR 169 to northbound I-405, then eastbound SR 900 to eastbound I-90. There’s no shortcut through Issaquah.
On I-405 itself, the impact won’t be limited to the closed southbound segment. WSDOT expects longer backups in both directions approaching Bellevue, meaning northbound drivers will feel the ripple effects even though their lanes stay open.
How travelers can navigate the weekend
WSDOT’s core advice: use transit where possible, take advantage of park-and-ride lots, and build flexibility into your schedule. Real-time conditions will be available through the WSDOT Travel Center map and the WSDOT mobile app — both worth checking before you leave, not after you’ve already been sitting in a backup for twenty minutes.
Signed detour routes will be in place for both the I-405 and SR 18 closures, giving drivers marked alternatives to follow.
One caveat applies across the board: the work is weather-dependent. If conditions don’t cooperate, closures could be rescheduled — shifting the disruption rather than eliminating it. Updates are available through the individual project webpages or by signing up for King County email alerts.
The SR 18 work extending through April 30 means this weekend isn’t a clean endpoint. Even after the major closures lift Monday morning, the right lane of eastbound SR 18 will remain a work zone for several more days. Drivers heading east out of the metro area should keep that in mind as the week gets underway — this stretch of highway isn’t done with its disruptions just yet.