King County Metro is spending $128.5 million on two RapidRide corridors under construction simultaneously: the future I Line through Renton, Kent and Auburn, and the J Line linking the University District, Eastlake, South Lake Union and Belltown in Seattle.

The I Line will add 17 miles of new RapidRide service in south King County when it opens in 2027. The agency positions the line as a response to demand for better north-south travel options in a corridor where riders will connect to the Renton Transit Center, Kent Transit Center and Auburn Station. The route will also tie into the existing RapidRide F Line, Sound Transit buses, the Sounder commuter rail line and local bus routes.

Construction activity on the I Line is currently concentrated at about a dozen bus stop sites across the three cities. Crews are installing sidewalks, curbs, gutters, ADA-compliant ramps and shelter footings, alongside underground electrical work, storm drainage and roadway paving. Most of this work began Sept. 9 and is scheduled to finish by Sept. 30, with the final Renton site running through Oct. 2.

The $128.5 million budget draws on $64.2 million from the Federal Transit Administration's Small Starts program, $9.6 million from the Federal Highway Administration, $6 million each from the Washington State Department of Transportation and the University of Washington, and $43 million from the city of Seattle — most of it from the voter-approved Levy to Move Seattle.

J Line past the halfway point

On the J Line, King County Metro reports construction is now more than halfway complete, a milestone the agency says means the most disruptive work is largely finished. Crews are completing the final sections of new street surface on Eastlake Avenue East after spending much of the project to date below the roadway.

The below-grade work included a full replacement of a 100-year-old water main in partnership with Seattle Public Utilities. Workers installed 9,000 feet of earthquake-resilient pipe, added 27 fire hydrants and coordinated 174 new service connections to nearby homes and businesses. Most storm drainage improvements across the project area are also complete, treating surface water along Eastlake Avenue East so it does not overwhelm sewer lines during major storms.

With utilities in place, crews have reconstructed and paved sections of the U District, Eastlake Avenue East and Fairview Avenue North.

The service case for the J Line rests on the density along its alignment. The University of Washington campus, which serves more than 50,000 students, gains a direct transit connection that the agency expects will offer students, staff and faculty an alternative to driving and parking. New stations will serve the UW clinic on Roosevelt Way Northeast and the Fred Hutch Cancer Center on Fairview Avenue North. The route then runs through South Lake Union and downtown Seattle, the city's principal employment hubs for tech, health care and service-sector jobs.

What riders and residents see next

The next construction phase brings the visible elements of the corridor upgrade: new bus stations with real-time arrival information and weather protection, brighter lighting, ADA-accessible sidewalks, and two miles of dedicated red bus priority lanes intended to cut travel times and improve schedule reliability. Concrete boarding islands will separate bus passengers from pedestrians at most locations, keeping sidewalk space available for businesses.

King County Metro has released measured progress for the J Line to date: 15,130 feet of repaired sidewalks, two miles of repaved streets, 3.7 miles of protected bike lanes, 177 improved crosswalks, 131 upgraded curb ramps, 33 intersections with new traffic signals and 190 newly planted trees.

Funding for the J Line comes from the voter-approved 2015 Seattle Transportation Levy, with support from King County Metro, WSDOT, the University of Washington, Seattle Public Utilities, the FTA and the FHWA.

The I Line remains the longer-dated deliverable: with stop infrastructure work in Renton, Kent and Auburn closing out by early October, the corridor is on track to enter service in 2027 and give south King County its first north-south RapidRide connection.