Interstate 405 (Washington) - Route Description

Route Description

I-405 begins as a continuation of Washington State Route 518 (SR 518) at the junction with Interstate 5 in Tukwila and almost immediately after the change to I-405, a High-occupancy vehicle lane begins, and continues to almost the end of the highway. The freeway continues on an easterly path, passing the newly renovated Westfield Southcenter shopping mall and crossing the Green River before approaching an interchange with SR 181. After the exit, the former Longacres race track, now owned by Boeing, and new Sounder commuter rail station for Tukwila is passed, and I-405 starts to head north-east towards a cloverleaf interchange with SR 167 and Rainier Avenue, which is the first exit in Renton. After the interchange with SR 167, the freeway, after a series of infamous s-curves, which become a traffic bottleneck during rush hour, turns to a northerly direction and intersects SR 169 and one direction of SR 900. A hybrid diamond interchange/partial cloverleaf interchange serves the other direction of SR 900 and the Gene Coulon Memorial Beach Park and a new development called The Landing.

Climbing Kennydale Hill, I-405 intersects N 30th St and Kennewick Place NW, which serves north Renton, and Kennydale, before quickly descending to another hybrid diamond/partial cloverleaf interchange with NE 44th Street, which provides access to Newcastle. I-405 now closely follows Lake Washington, and enters a wooded section until an interchange with Lake Washington Boulevard and 112th Ave SE which serves both a park and ride station and the community of Newport Hills. The final interchange before I-90 is a diamond interchange serving Coal Creek Parkway.

Factoria Mall is east of I-405 as it approaches a full stack interchange with Interstate 90 which provides access to Seattle, Mercer Island, as well as the Eastgate neighborhood of Bellevue and Issaquah. Mercer Slough is west of I-405 as it heads towards downtown Bellevue. A 2008 construction project demolished the Wilburton Tunnel which formerly covered a portion of the freeway between Factoria and Bellevue.

The historic Wilburton Trestle passes I-405 as a diamond interchange with SE 8th Street connects the freeway to South Bellevue and the Lake Hills area. In quick succession is a short diamond interchange with NE 4th Street, a full cloverleaf with NE 8th Street, serving downtown Bellevue and Overlake Medical Center, and an HOV only left exit to the Bellevue Transit Center and NE 6th Street. SR 520 which provides access to Medina and Redmond, home of the Microsoft Corporation is the next interchange, with a half cloverleaf interchange with several fly-over ramps to allow complete access to and from SR 520.

Bridle Trails State Park borders the freeway on the east side, while Watershed Park and Northwest University are on the western side of the freeway as it approaches NE 70th Place, serving Houghton and Snyders Corner before approaching a full cloverleaf with former SR 908 serving Kirkland. An incomplete interchange with NE 116th Street comes before I-405 connects to Totem Lake via an interchange with NE 124th Street and an HOV only left exit to the Evergreen Hospital and NE 128th Street. NE 160th Street is the next interchange before I-405 crosses over the Sammamish River and connects to SR 522 which provides access to downtown Bothell and Woodinville. An interchange with NE 195th Street provides access to the local business park and the University of Washington Bothell branch.

Entering Snohomish County at mile post 25, I-405 enters a wooded area before coming to an interchange with the Bothell-Everett Highway (SR 527), which is the final interchange before I-405 terminates at an interchange between Interstate 5 and SR 525.

As of 2007, the most heavily traveled section of I-405 is near SE 8th Street in downtown Bellevue, with an daily average of 200,000 cars per day traveling through this segment. This number was slightly lower in 1997, with 190,000 cars per day, but has dramatically increased since the first measurement in 1967, with 32,600 cars per day traveling through Bellevue.