Traffic Lab is a Seattle Times project that digs into the region’s transportation issues to explore the policies and politics that determine how we get around and how billions of dollars in public money are spent.
Under a nearly full moon and the gaze of giddy rail fans, Sound Transit accomplished a necessary feat, by running an electric-powered railcar across the I-90 floating bridge.
The first trip, completed early Tuesday from the Eastside to Seattle, lumbered along at walking speed, then reversed direction back to Mercer Island.
After that, operators went back-and-forth on the eastbound track “not once, but many times at speeds up to 55 mph,” said executive project director Tony Raben, in an email to colleagues. Similar overnight trips, on the westbound rails, were scheduled again for early Wednesday.
“Let’s carry this momentum forward with confidence and optimism,” Raben’s message said.
Next comes a season of practice trips, before the public can finally ride across Lake Washington between Bellevue and Seattle. Sound Transit is on pace to open the I-90 crossing, and stations at Mercer Island and Judkins Park, in spring 2026. Four-car trains, labeled as the 2 Line, will travel all the way from Redmond to Lynnwood, sharing track in North Seattle with the older 1 Line.
The lake crossing is expected to not only transform transit in the region, but make history as the world’s first light rail system to run on a floating bridge.
It’s a challenge the Washington State Department of Transportation and Sound Transit’s consultants have worked on since 2005, when they drove trucks loaded with 600 tons to confirm the bridge would stay buoyant under heavy trains. Besides that, they must ensure train wheels stay secure on fixed rails even though the bridge shape fluctuates.
Three dozen supporters brought cameras and pizza to witness Monday night’s event, the vibe similar to Blue Angels fans at Seafair who show up in Seattle’s East Portal Park, which perches over the west lakeshore and freeway.
At nearly the same moment the railcar first entered the I-90 bridge from the Mercer Island side, 11:49 p.m., a thick shower of sparks streaked high above the park, from an apparent meteor or satellite junk.
“The little train that could!” a witness shouted several minutes later, when the Siemens-brand railcar arrived and vanished into the Mount Baker Tunnel. Applause broke out. Transit-board member Claudia Balducci of Bellevue received a double high-five. “It’s surprisingly exciting, for a 10 mph train trip,” she said.
Construction has been plagued by problems that have delayed by almost three years the 2023 expected start of service. Before that, the East Link program missed its promise on the 2008 ballot to operate by 2020.
The night’s test runs were devised partly to demonstrate that Sound Transit can control stray current, which might otherwise penetrate the concrete track ties and highway decks, corroding steel rebar. That in turn would weaken the bridge pontoons over decades, and jeopardize WSDOT’s plan for the I-90 Homer Hadley Bridge, built in 1989, to last 70 more years.
“The results confirmed that our protection systems are performing as designed — preventing stray current or capturing it before it enters the bridge,” Raben reported.
Among other nuances, transit engineers kept the trackway dark, the better to measure any electric arcing between the overhead power lines and the railcar. The first trip showed virtually no arcing, a positive sign.
Engineers are also monitoring eight flexible track joints, where the fixed bridge spans meet the pontoons, and lake levels fluctuate 2 feet per year. High-strength seismic dampers, which undergird the roofs of Seattle stadiums, are being adapted to rail, called a “brilliant solution” locally and being watched worldwide.
Many years ago, the question arose whether trains must go slower, perhaps 35 mph. Engineers even scrapped an early joint design that depended on too many moving parts. But since the mid-‘10s, project managers have expressed confidence trains can go full speed, as demonstrated a few times Tuesday morning.
Commuters and politicians have dreamed of trains over the lake since at least 1970, when the corridor appeared in the Forward Thrust series of public works ballot measures, but failed to pass.
It showed up again in the regional vision maps when Sound Transit formed in the early 1990s, but didn’t get funded until the ST2 sales-tax measure of 2008 — with a promised start by 2020. The I-90 segment will be almost six years late, for many reasons, chiefly a route dispute in Bellevue and later, a contractor’s rebuild of 5,400 concrete track ties Sound Transit considered too weak. A final step was certifying with WSDOT that devices to control stray current, including fine-tuned monitors inside the hollow pontoons, were fully reliable.
With I-90 rails not operable yet, the agency is running a 10-station Eastside starter line from South Bellevue to downtown Redmond, carrying just over 10,000 daily passengers.
Sound Transit towed a railcar across the I-90 bridge in May, at low speed, to test its clearances. As the I-90 segment missed a July goal for an electrically powered trip, CEO Dow Constantine and the governing board moved the three-station Federal Way extension ahead in line. Federal Way Link’s grand opening is scheduled for Dec. 6.
The new tracks were built in the former express lanes of I-90, which the federal government intended to someday carry high capacity transit.
Sound Transit’s corridor budget is $3.7 billion, from Redmond Technology Station to International District/Chinatown Station. Of that, contracts for the cross-lake segment total $765 million, not including trains and signals, but main builder Kiewit-Hoffman is seeking a potential $250 million more, a Seattle Times analysis found, and recent project reports warned of possible overruns.
When finished, the full 2 Line is supposed to carry 50,000 daily passengers, but that target remains uncertain, due to work-from-home trends, competition from employer-funded private transit, and weak commuter bus demand. But light rail riders have gradually increased since the pandemic, to a total 111,000 per day in July, as new stations opened on both sides of the lake.
After the celebrations in Federal Way, followed by the new link over I-90, a construction lull and a sober task confront Sound Transit: how to deal with a newly revealed $30 billion long-term funding gap, that jeopardizes projects in Tacoma, Everett, West Seattle or Ballard in the 2030s and 2040s.