Some transportation challenges are measured not in miles, but in constraints. Crossing Lake Washington meant working with a structure that responds to its environment rather than resisting it.

When the Link 2 Line opened on March 28, 2026, riders experienced something no transit system had ever delivered before: light-rail vehicles traveling across a floating bridge. For passengers, the trip feels routine. For those of us who worked on the project, it represents years of careful engineering, testing and collaboration aimed at making something unprecedented operate safely and reliably every day.

The Crosslake Connection forms the final seven miles of the Link 2 Line, connecting downtown Seattle with Mercer Island and the Eastside communities of Bellevue and Redmond. It introduces a new high-capacity transit option for this critical regional corridor. One of the most remarkable features of this project is that these trains cross the Homer M. Hadley (HMH) Floating Bridge, a 1.2-mile structure that responds to wind, waves, temperature and traffic in ways fixed bridges do not.

That reality shaped every major design and construction decision related to the lake crossing.

Innovating Solutions on a Floating Structure

The HMH Floating Bridge carries Interstate 90 and the Link 2 Line across Lake Washington, a deep glacial lake separating Seattle from Mercer Island and the Eastside communities of Bellevue and Redmond. The HMH Floating Bridge rises and falls with lake-level changes, deflects under live loads, and responds to wind and waves acting across the bridge’s large surface area. But for rail systems, track gauge must remain consistent, ride quality smooth and movement within acceptable ranges.

The team’s solution to the challenge of floating bridge movement was a patented “track-bridge” system that spans each of the bridge’s four major expansion joints, accommodating the daily movements of the floating structure. The track bridge allows the rails to move with the bridge while distributing that movement over a sufficient length to provide safe, comfortable rail operations.

We knew early on that traditional rail solutions weren’t going to work here. The bridge moves—so the rail system had to move with it, not fight it.

To strengthen the structure and extend its lifespan, KPFF Consulting Engineers, part of WSP’s team, designed a retrofit that added 20 new external post-tensioning tendons, each exceeding 3,000 feet in length to the interior of the floating bridge. These tendons increase the bridge’s longitudinal strength and manage forces generated by train operations, highway traffic and environmental conditions.

To protect the floating bridge pontoons from stray current, WSP and team member David Evans and Associates implemented a noninvasive rail-attachment strategy that avoided drilling into the tops of the concrete pontoons. The team designed an attachment system consisting of precast concrete blocks that support the rails and are electrically isolated and epoxied to the bridge deck. This system utilized a novel approach with existing products to protect the bridge’s long-term health and meet the requirements of the bridge owner, the Washington State Department of Transportation.

Environmental considerations also shaped design decisions. Beneath the fixed approach spans, engineers developed a seismic retrofit strategy that eliminated in-water construction. This protected Lake Washington’s ecosystem while improving structural resilience and reducing construction scheduling complexity.

Testing and Proof of Performance

Designing a first-of-its-kind system demanded rigorous verification in the lab and the field.

To validate the track-attachment system design, WSP led extensive prototype testing of the precast block design in conjunction with the University of Washington. Prototype blocks were cyclically loaded through hundreds of thousands of load cycles, which confirmed that the design performed as intended—as a safe and reliable track attachment to the floating bridge.

During construction and operational testing, teams from WSP and KPFF measured real-time floating bridge deflections under light-rail vehicle live loads as trains passed. These measurements validated the analytical models developed by KPFF and demonstrated that the floating bridge structure performed as expected.

A New Era for Regional Mobility

The Link 2 Line is more than an engineering achievement. It’s also a substantial boon for thousands of daily travelers, offering faster and more reliable trips across Lake Washington and direct connections to jobs, universities, medical facilities and cultural destinations. New stations feature public art and architectural elements that reflect local identity, such as Judkins Park Station, which features artwork depicting rock-and-roll icon and Seattle native Jimi Hendrix.

The experience of crossing the lake by rail also is distinctly Pacific Northwest. Riders take in the expanse of Lake Washington with the Cascades and Mount Rainier beyond—a reminder that transportation can be both functional and inspiring.

Major infrastructure succeeds when it’s made with strong partnerships. From early design through testing and construction, the remarkable results of the Crosslake Connection required creativity, precision and commitment across a diverse team serving Sound Transit.

Now that the line is open, I measure the project’s success by the benefits it brings our local communities: safe, reliable and sustainable transportation.

Editor’s Note: Paula Hammond will resume writing her Transportation Troubleshooting column in August 2026.