I-405 drivers to get triple-deck interchange at Kirkland

Sound Transit board members approved a $287 million deal Thursday to fund a unique triple-decker interchange on I-405 through Kirkland, where bus stations and pedestrians will share the road with ramps for freeway toll lanes.

Construction will be managed by the Washington State Department of Transportation under the agreement.

WSDOT will replace the cloverleaf I-405 interchange at Northeast 85th Street so it becomes part of the Express Toll Lanes system.

The new bus service — known as ST Ride or “Stride” — was promised by 2024 in the voter-approved, $54 billion ST3 ballot measure in 2016. Projects are late, in part because of funding delays for WSDOT’s related highway program.

Sound Transit could have approved the deal last year but postponed the vote until the board worked details of new project schedules across the region, said Claudia Balducci, a Metropolitan King County Council member from Bellevue. The transit agency faces a $6.5 billion funding gap, leading to delays in several rail and bus extensions.

Preliminary schedules call for Stride to open in 2026 for a Bothell-Kenmore-Shoreline route on Highway 522, and 2026 for Burien-Renton-Bellevue using I-405 and Highway 518. The I-405 route from Lynnwood to Kirkland and Bellevue is now aimed for 2027.

Bus ridership is projected at 19,200 to 25,800 daily passengers, using 11 stations along 37 miles of I-405 and 518. The Kirkland interchange accounts for just over one-fourth of the $1 billion budget for Stride on I-405. Other components include buses, a Bothell-area maintenance base, median stations, park-and-ride space and a planned Tukwila station at Highway 518.

Planners have also added a “kiss-and-ride lot” on the second level, where transit customers can be dropped off by friends or ride-hailing cars, said Sound Transit project director Paul Cornish.

It also gives Kirkland more access to the WSDOT Express Toll lanes, where currently there’s a 7-mile gap between Totem Lake and downtown Bellevue. Likewise, the Stride buses would roll for the last 7 miles toward the Bellevue Transit Center with no stops, unless they gain a station at 85th.

“It’s a great example, where we’re making highway improvements that do not add any general lane capacity to the system, but at the same time we’ll move more people than if we were adding general-lane capacity,” said WSDOT Secretary Roger Millar, a transit-board member.

The Kirkland interchange can be seen as using transit dollars to aid highway users. On the other hand, WSDOT’s upcoming Renton projects benefit buses, with new ramps and quick toll lanes, that otherwise wouldn’t happen under ST3. Illustrating the horse-trade underway, a board presentation mentioned that $260 million will “be reimbursed to Sound Transit” as credits for transit to use state right of way, and for fish passage improvements.

The site is part of WSDOT’s $4 billion program that adds toll lanes, exit-only lanes and improved bus access to I-405 and linked Highway 167, serving the suburban crescent around Lake Washington. Gov. Jay Inslee recently proposed using $300 million in federal pandemic recovery funds to help solve a $500 million funding gap, as I-405 costs soar.

Early documents predicted only 300 to 1,000 people per day would board Stride buses at isolated Northeast 85th Street. However, Kirkland is writing a plan to encourage infill development, such as apartments in the adjacent Rose Hill area, which supporters say will make Stride more popular. The city’s nearly completed plan calls for 8,152 housing units and 22,751 jobs near the station over 23 years, nearly quadruple current density.

At the new interchange, scheduled for 2026, pedestrian conditions will be superior to the 1970s-era cloverleaf because the shape includes walk-bike trails separate from the roadway, at a maximum 5% grade to the second level.

However, Sound Transit’s published design images show that transit users (or anyone who walks or bikes between western and eastern Kirkland) must share the second-level roadway with not only buses but also the drivers going to and from I-405 toll lanes, using crosswalks within a traffic oval that resembles a roundabout. Sound Transit board members didn’t ask questions Thursday about walking safety. Time is available during final design and bidding, if elected officials and advocates choose to take a closer look.