Sound Transit LRV achieves world-first on Seattle’s floating bridge

A significant milestone was achieved on Sound Transit’s East Link Extension light rail project as, for the first time in history, a light rail vehicle (LRV) operated under its own power across the I-90 floating bridge. The LRV departed Mercer Island Station and traveled toward Seattle, drawing power from the overhead catenary system as it crossed Lake Washington.

The test was closely monitored by engineering teams overseeing traction power, catenary interaction, wheel-rail dynamics, and communication systems in real time. The LRV operated smoothly on its first attempt, validating the integration and performance of multiple systems working together under live conditions.

The Sound Transit LRV crosses the I-90 floating bridge (Photo courtesy of Sound Transit)

For more than seven years, Mott MacDonald has served as part of Sound Transit’s construction management consultant team, providing project management leadership, contract administration, and technical oversight. The team has been instrumental in coordinating complex systems integration - verifying traction power systems adapted to bridge movement, validating signaling and communications, assessing stray-current and cathodic-protection systems, and ensuring safe, reliable performance under dynamic bridge conditions.

“This milestone is more than an engineering success - it reflects the leadership, expertise, and innovation of our people, along with the persistence required to overcome challenges once thought impossible,” said Guil Pereira, Resident Engineer at Mott MacDonald.

The East Link Extension, part of Sound Transit’s system expansion program, will help meet the Puget Sound region’s rapid population and employment growth by providing faster, cleaner, and more reliable connections across Lake Washington. When it is completed in early 2026, the 2 Line will link Redmond, Bellevue, Mercer Island, and Seattle, enhancing mobility throughout the region.