Lake City Way (SR 522) northbound in the commercial district of Lake City
SR 522, named Lake City Way within Seattle city limits, begins at an interchange with I-5 in the Roosevelt neighborhood of northern Seattle, east of Green Lake. The interchange only allows movements south towards Downtown Seattle on I-5, and includes a connection to the freeway's reversible express lane system. The highway travels northeast from the interchange, tunneling under the intersection of Roosevelt Way NE and NE 75th Street; the intersection itself is connected to SR 522 by a series of ramps to collector streets. Lake City Way continues northeast through Maple Leaf as a four-lane arterial street before turning north on its approach to Thornton Creek. After crossing the creek, the highway enters the Lake City neighborhood, passing several car dealerships. Lake City itself is a designated urban village, with mixed-use development and apartment buildings that are centered around the intersection of Lake City Way between NE 125th Street and NE 145th Street. At NE 145th Street, SR 522 intersects SR 523 and crosses into Lake Forest Park.
Beyond Seattle, the highway is named Bothell Way and follows the northern shore of Lake Washington. SR 522 intersects Ballinger Way (SR 104) at the central shopping center in Lake Forest Park, and is joined by the Burke-Gilman Trail, a multi-use trail running along the lakefront on a former railroad grade. Bothell Way continues east along the northern shore of Lake Washington through the city of Kenmore, located on the mouth of the Sammamish River and home to the Kenmore Air Harbor seaplane base. SR 522 travels upriver through a narrow valley that makes a sharp turn north towards Bothell. The highway turns east and continues downhill of the city's downtown business district, staying near the Sammamish River (and the Sammamish River Trail) and intersecting Bothell Way (formerly SR 527). Leaving Bothell, SR 522 then travels around the southern edge of University of Washington Bothell campus and intersects I-405, becoming a grade-separated freeway.
East of I-405, SR 522 enters Woodinville and follows Little Bear Creek as it turns north away from the city's downtown, intersecting SR 202. The freeway enters Snohomish County and intersects SR 9 south of the Brightwater sewage treatment plant. It continues through several sharp turns that follow the Eastside Rail Corridor, a former railroad grade that runs northeasterly through the predominantly rural area near
Grace. In Maltby, the freeway reaches an at-grade intersection with Paradise Lake Road (SR 524) and becomes a two-lane undivided highway. SR 522 travels northeast from Maltby, intersecting Echo Lake Road in a single-point urban interchange, and crosses the Snohomish River into Monroe. Within Monroe, the highway widens to a four-lane freeway with median separation and intersects Main Street in a dogbone interchange near the Monroe Correctional Complex. SR 522 cuts across suburban housing areas in Monroe, and crosses over US 2 and the BNSF Railway near the Evergreen State Fairgrounds. The highway makes a 180-degree turn south to intersect with US 2, where it terminates; the intersection also has a direct offramp for eastbound traffic from SR 522 to eastbound US 2.
The entire route of SR 522 is designated as part of the National Highway System, classifying it as important to the national economy, defense, and mobility. The State of Washington also designates the SR 522 corridor as a Highway of Statewide Significance, which includes highways that connect major communities throughout the state. The highway is the primary route for Seattle-area residents to access Stevens Pass and other parts of the Cascade Mountains. SR 522 is maintained by the Washington State Department of Transportation (WSDOT), which conducts an annual survey on the state's highways to measure traffic volume in terms of average annual daily traffic. In 2016, WSDOT calculated that 96,000 vehicles used SR 522 at its interchange with I-405 and 12,000 vehicles used it at its eastern terminus in Monroe, the highest and lowest counts along the highway, respectively.