SR 520 Trail Grade Separation

Rendering of artwork for SR 520 tunnel showing pedestrians in tunnel with palm trees and rainbow.

Project Overview

Washington State has provided funds to grade separate the 520 Trail from vehicles at NE 40th St. The project will construct a tunnel under NE 40th St near the westbound SR 520 ramps. During construction, a detour for trail users will be in place along NE 36th St, 150th Ave NE, and NE 51st St (SR 520 Trail Detour (PDF)).

Pedestrian and Bicycle Improvements

The tunnel will enhance safety by moving much of the pedestrian and bicycle traffic away from the vehicular traffic on NE 40th St. Travel times will also be reduced as tunnel users will not have to wait for the traffic signal. The tunnel is expected to attract additional walking and biking traffic to the area by increasing access to the freeway flyer stop, the Redmond Technology Light Rail Station, and Microsoft.

Trail Grade Plan View showing planned configuration

17-Day Closure of NE 40th Street

For 17 days in August 2020, NE 40th Street was closed at the west side of the SR 520 on/off-ramps. During this time, construction crews excavated the tunnel, installed the sides and roof, covered the structure and repaved NE 40th St. This full closure dramatically reduced the overall length of the construction project.