A Link light rail vehicle successfully crossed the I-90 floating bridge under its own power in Seattle, marking the first time in the world that a train powered across a floating bridge.

Train Crosses Floating Bridge

The test was conducted on the Homer M. Hadley Memorial Bridge, which carries Interstate 90 across Lake Washington. Sound Transit described the event as a “historic milestone,” as powering trains across a floating bridge is considered one of the most complex challenges in rail engineering.

According to Interesting Engineering, this feat has challenged engineers for decades. The East Link project began in 2016 and was originally scheduled to open in 2023. Though budget and technical setbacks pushed the timeline back, this successful test crossing marks a major milestone in the effort to link Seattle and its Eastside communities.

During the test, a single light rail train made several trips across the bridge. Beginning at speeds of about 5 miles per hour, crews gradually increased speed until the train reached its full operating speed of 55 miles per hour. The late-night timing of the test also allowed engineers to observe expected electrical arcing between the train and its overhead power lines.

In the coming months, tests will continue to be conducted between Mercer Island and Judkins Park. Sound Transit 2’s Line, which will connect downtown Seattle, Bellevue, and Redmond Technology Station at Microsoft’s headquarters, is scheduled to open in early 2026.

The project will make commutes for workers at Microsoft, Google, Meta, Amazon, and other companies much faster and more reliable, as current commutes can take between 20 minutes and two hours, depending on traffic patterns.

The first part of the 2 Line opened in early 2025, stretching over three miles and carrying over 10,000 passengers daily. This portion of the line is in Downtown Redmond and takes passengers from Marymoor Park to Downtown Bellevue in just 15 minutes.