bores between the extension's three stations. The southernmost section of the extension passes under the University of Washington campus and required several mitigation measures to reduce electromagnetic interference for laboratory equipment, including rubber dampeners on floating slabs of track and the relocation of sensitive equipment at four facilities. The Northgate extension opened on October 2, 2021, adding three stations to the line's north end. Route The northern terminus of the 1Line is Northgate station, located adjacent to the Northgate Mall along Interstate 5 in North Seattle. The line heads south along an elevated guideway that dives into the Northgate Link tunnel in the Maple Leaf neighborhood. The tunnel travels southeast through Roosevelt, serving a station near Northeast 65th Street, and south to U District station before reaching the University of Washington campus. The tunnel travels southeast under the campus to University of Washington station, located near Husky Stadium, from which it heads south in the University Link tunnel, crossing under the Montlake Cut of the Lake Washington Ship Canal and State Route 520 before taking a turn to the southwest. The tunnel climbs Capitol Hill and passes under Interlaken Park and Volunteer Park before turning due south to enter Capitol Hill station on the east side of Broadway. The tunnel makes a gradual turn to the west, dipping as far south as East Union Street, and crosses under Interstate 5 at Pine Street. It merges into the Downtown Seattle Transit Tunnel within the Pine Street Stub Tunnel, where it formerly merged with buses from Convention Place station. The downtown transit tunnel, formerly shared between light rail trains and buses, travels west under Pine Street through Westlake station and south on 3rd Avenue through University Street and Pioneer Square stations in Downtown Seattle. The tunnel ends at International District/Chinatown station, adjacent to King Street Station (served by Amtrak and Sounder commuter rail), and the 1Line travels south through SoDo along the east side of the SODO Busway. The SoDo section has two stations, Stadium and SODO, and includes several gated crossings. From SODO station, the track ascends to an elevated guideway traveling east along South Forest Street, passing the line's railyard and maintenance facility. The elevated trackway passes over Airport Way and comes to rest on an embankment under Interstate 5, entering the Beacon Hill tunnel. The Beacon Hill tunnel travels approximately under Beacon Hill, serving a station at Beacon Avenue