Innovative Tubular Structure to Support Northgate Pedestrian and Bicycle Bridge


The Northgate Pedestrian and Bicycle Bridge will span Interstate 5 at 100th Street N, connecting a dense hub of transit-oriented development at the Northgate Transit Center with North Seattle College and adjacent residential neighborhoods. Long identified as a missing link in the transportation network of the rapidly developing Northgate neighborhood, which includes bus and planned light rail connections, the structure will be one of the longest pedestrian bridges in the country at a total length of 2,060 feet. As the most visible pedestrian overpass in Seattle, the bridge will make an iconic visual impact with its highly efficient tubular structure that morphs organically in response to sensitive ecological habitat and complex urban conditions. The bridge’s X-shaped cross members enclose a 20-foot wide walking surface, integrating guardrails, throw barriers, handrails, lighting, and drainage systems into a singular form. To make this daring design possible, the LMN Tech Studio developed a series of custom cast-steel nodes at the intersections of each member, making the assembly lighter and stiffer, with more accurate and efficient construction.

LMN’s design for the bridge has reached a 30% completion milestone, with construction expected to be complete in 2018.