If you’re driving on I-5 north of Seattle to work the night shift, deliver cargo or visit friends this weekend, be prepared for overnight freeway closures.

Northbound I-5 will close at Mountlake Terrace Friday, Saturday and Sunday nights at 11 p.m. All northbound traffic must exit to Highway 104, where signed detours will lead traffic to northbound Highway 99. Lanes will reopen at 6 a.m. Saturday, 6:30 a.m. Sunday and 4:30 a.m. Monday.

Those overnight lane closures allow contractors to build temporary framework for a concrete light-rail bridge near Mountlake Terrace Station. A similar weekend-night job closed southbound I-5 lanes in November.

Traffic Lab is a Seattle Times project that digs into the region’s thorny transportation issues, spotlights promising approaches to easing gridlock, and helps readers find the best ways to get around. It is funded with the help of community sponsors Alaska Airlines, Kemper Development Co., Madrona Venture Group, NHL Seattle, PEMCO Mutual Insurance Company and Seattle Children’s hospital. Seattle Times editors and reporters operate independently of our funders and maintain editorial control over Traffic Lab content.

Southbound I-5 will close one night in downtown Seattle this weekend, from 11 p.m. Friday until 5 a.m. Saturday, for an inspection of fire-protection systems below the Washington State Convention Center.

A signed detour will divert drivers to the Stewart Street exit and surface streets, then return to I-5 at James Street. Or use the express lanes, which will stay open pointed south, to bypass downtown. Mercer Street and Yale Avenue onramps southbound will be closed.

Advertising

Also, the low-level West Seattle bridge will close Saturday from 8 a.m. to 1 p.m. as the city inspects a system that latches two swinging spans together. Only emergency vehicles may cross, while all other users, including pedestrians and bicyclists, must detour.

Since last spring, the bridge has been off limits anyway from 5 a.m. to 9 p.m., except for buses, trucks, first responders, preregistered van pools and maritime workers with permits.

Link light-rail trains will serve all stations, unlike last weekend, when University of Washington Station closed during late-night train tests in the UW-to-Northgate extension, which will open by September.

I-5 in Pierce County is also scheduled for overnight construction this weekend. Traffic will be reduced to one lane each direction at Joint Base Lewis-McChord from 11:59 p.m. Friday until 5:30 a.m. Saturday.