Like much of the public, Sound Transit leaders are sick of watching tracks and stations sit unused in Bellevue and Redmond. So, they are aiming to open an Eastside-only starter line in March.

Trains will make eight stops between Redmond Technology Station, which adjoins the Microsoft campus, and South Bellevue Station, which is equipped with a new 1,500-stall park-and-ride garage.

This will be the start of light-rail service on the Eastside, arriving as Sound Transit’s full extension there is burdened by massive construction delays in the former express lanes of Interstate 90, where trains won’t cross Lake Washington between Bellevue, Mercer Island and Seattle’s International District/Chinatown Station until 2025.

Contractors are rebuilding more than 5,000 defective concrete track ties, known as plinths, in the I-90 segment. The whole 14-mile, $3.7 billion route, approved by voters in 2008, was aimed at 2020 in the ballot measure but lost three years to planning disputes in Bellevue. It was supposed to open last month if construction had stayed on track.

Sound Transit’s governing board voted Thursday to advance $37 million for 2024 starter-line operations, following an earlier $6 million outlay for research, training and signal revisions. Full-speed practice trips would begin in November.

Passengers can expect service on the new line every 10 minutes for 16 hours a day, with trains that can hold a total of 400 people in two railcars. There aren’t enough workers and railcars yet for longer trains, which probably won’t fill anyway along this initial segment.

An estimated 6,000 riders per day are expected to use Eastside light rail next year. Commuters could travel between Redmond Technology Station and the Bellevue Downtown Station in 10 minutes.

John Chelminiak, a former Bellevue mayor, said he recalls discussing Sound Transit during his first City Council meeting in 2003. “That was 20 years ago. The rails are in. They’re ready to go. Let’s put the trains on the tracks, and get the East Link Starter Line moving,” he said. “It will build ridership, for when the whole thing is open.”

The political push for a starter line began last summer, led by transit board member Claudia Balducci, a Metropolitan King County Council member from Bellevue. Transit board Chair Dow Constantine, the King County executive, and member David Baker, a Kenmore City Council member, have been especially supportive, she said.

“I can’t remember a time when the agency has adapted as quickly, and thoroughly, as they did in this case,” Balducci said. “I really look forward to getting on a train and riding it in East King County.”

March 2024 remains a goal, not a certainty.

There is a risk that either the Federal Transit Administration won’t complete a required safety and readiness review by winter, or that there will be too few workers to complete the job, said a memo by Sound Transit CEO Julie Timm. On the other hand, she reported that 82% of the 116 operating positions have been filled by King County Metro, which runs the light-rail system.

If all goes as planned, the Bellevue opening would be followed by service between Northgate and Lynnwood six months later. At first, the Lynnwood line would operate at reduced capacity, until more railcars arrive from Siemens in Sacramento, Calif., and the I-90 trackways open, allowing trains to move between the new Bellevue maintenance base and Seattle.

Snohomish County’s three transit board members were previously worried that a Bellevue line would siphon people and time away from a prompt Lynnwood grand opening, but that dispute appears settled, and a fall 2024 startup might be only three months past the July 2024 target set when construction started.

The Lynnwood line’s four new train stops — at Shoreline South/148th, Shoreline North/185th, Mountlake Terrace and Lynnwood City Center stations within view of Interstate 5 — are projected to attract 25,000 to 34,000 daily passengers next year, Timm reported. Eventually, the Eastside trains are supposed to turn north after crossing Lake Washington, for double service through downtown Seattle and the University District to Lynnwood. A future station is being built at Northeast 130th Street in Seattle.

Everett Mayor Cassie Franklin pointed out that Lynnwood line ridership is eight times as high as the initial Eastside segment. The board passed her amendment that commits to supplying extra buses, in the event trains in Snohomish County and North Seattle become overcrowded.

Two more Eastside stations, at Marymoor Park and downtown Redmond, should open in spring 2025.

The unfinished south corridor from Angle Lake to Federal Way isn’t expected to open until 2026. It’s delayed mainly by unanticipated wetland soil, forcing builders to design a long-span bridge over the trouble spot.

Sound Transit is now preparing to celebrate its long-awaited T Line streetcar extension, winding from downtown Tacoma to the Stadium and Hilltop neighborhoods, scheduled to open Sept. 16.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com; on Twitter: @MikeLindblom. Staff reporter Mike Lindblom covers transportation for The Seattle Times.