A three-car rollover crash on northbound Interstate 5 just north of Mercer Street snarled Seattle's Thursday morning commute, blocking multiple lanes near milepost 167 and sending one person to the hospital with head pain. One vehicle flipped onto its roof during the roughly 9 a.m. collision, and its occupants self-extricated safely.
The Washington State Department of Transportation reported that the crash blocked three right lanes on northbound I-5 near Mercer Street, while the Washington State Patrol described it as a three-car rollover and said the right two lanes were shut down. KOMO News reported that KOMO News confirmed the Washington State Patrol urged drivers to use caution through the area as crews worked the scene.
Seattle Fire Department crews arriving on scene found multiple vehicles involved, including the overturned car, but found that its occupants had already self-extricated safely. Firefighters evaluated three patients at the scene and reported all three were in stable condition, with just one suffering an injury, before downgrading their response. According to KING 5, dispatchers had initially received reports of occupants trapped inside the overturned vehicle, but arriving firefighters quickly confirmed that was not the case.
A Notoriously Dangerous Stretch of Freeway
The crash site sits within a corridor characterized as particularly hazardous. A legal analysis by Elk & Elk uses 2015–2024 WSDOT data and cites a previous study based on NHTSA fatal-crash data from 2000–2019 that identified the stretch of I-5 between exits 161 and 169 — which includes the Mercer Street exit at milepost 167 — as the deadliest 10-mile stretch of freeway in Seattle.
Citywide, the numbers underscore how common these incidents are. The Advocates reported that WSDOT collision portal data show Seattle recorded 6,108 traffic crashes in 2025, including 25 fatal collisions and nearly 1,200 crashes resulting in confirmed injuries, according to The Advocates.
Thursday's rollover was far from the first serious incident near this interchange. KIRO 7 reported a crash near Mercer. And in December 2022, a crash involving two U.S. Navy buses on I-5 near Mercer Street injured 18 people on a Monday morning, blocking two right lanes and the Stewart Street off-ramp, per MyNorthwest.
Construction Adds to the Squeeze
Any lane closure along this stretch carries outsized consequences because of how much traffic the corridor carries. WSDOT estimates that approximately 240,000 vehicles travel daily across the I-5 corridor through downtown Seattle near the Ship Canal Bridge, making morning lane closures highly disruptive to regional traffic flow.
That disruption is compounded by ongoing construction. Under WSDOT's 2026 Revive I-5 project, northbound express lanes now operate 24 hours a day to cushion mainline lane reductions, meaning even a relatively minor northbound crash can trigger severe backups.
Washington's Seat Belt Law
Firefighters evaluated three patients at the scene, with one suffering head pain. Under RCW 46.61.688, Washington enforces a primary seat belt law that lets officers stop unbuckled drivers directly, with violations carrying a $124 traffic infraction penalty, according to the Brumley Law Firm.
Thursday's rollover added another entry to the long list of collisions that have disrupted one of Seattle's busiest and most accident-prone highway corridors.
