The Washington State Department of Transportation (WSDOT) announced a series of lane restrictions on State Route 18 (SR 18) near Tiger Mountain, affecting commuters and freight operators throughout the first half of September. Starting at 9 p.m. on September 10, the eastbound lane will be reduced to a single open lane until 5 a.m. the following morning. This restriction repeats on September 11, 13 and 14.
What drivers need to know
During the nightly closures, only one eastbound lane will remain open. Motorists are urged to allow extra travel time and consider alternate routes. Freight traffic, in particular, should divert to westbound SR 169, then merge onto northbound I‑405, and continue on northbound I‑405 to eastbound I‑90, or use any other suitable state routes that avoid the restricted segment.
Why the closures are happening
The lane reductions are part of preparatory work for the upcoming widening of SR 18 between Issaquah‑Hobart Road Southeast and Deep Creek. Crews will be surveying the corridor during the night‑time closures to gather data needed for the future construction. Although the survey work begins now, the actual widening construction is not expected to start until the summer of 2030.
Additional closures later in September
A separate single‑lane closure on westbound SR 18 is scheduled for six consecutive nights beginning September 15. Furthermore, a full eastbound closure will occur nightly from 9 p.m. to 5 a.m. for six nights starting Wednesday, September 23. Drivers should plan accordingly and stay informed of any updates posted by WSDOT.
How to stay informed
WSDOT will provide ongoing updates on the project and any changes to the schedule at wsdot.wa.gov/construction‑planning. Residents are encouraged to check the site regularly for the latest information, including any additional detour recommendations or traffic advisories.
Impact on the community
While the temporary lane reductions may cause inconvenience for commuters, the long‑term goal is to improve traffic flow and safety on a key east‑west corridor in King County. The widening project aims to accommodate growing traffic volumes, support local businesses, and enhance connectivity between the Issaquah area and the broader Seattle‑Tacoma region.
Original reporting: Renton Reporter — read the source article.
