Transitioning rail to a floating bridge that is constantly bobbing and swaying at the whims of the water required a first-ever solution for Sound Transit. Linking Seattle to points east across Lake Washington, the nearly one-mile-long Interstate 90 floating bridge—one of the world’s longest—was earmarked to receive light-rail service to connect Seattle and Bellevue. But settling on a finished solution wasn’t simple.
The issue centered on how Sound Transit could install rails on a bridge that uses accordion joints to transition from a fixed structure to a floating structure that, due to water levels, rises and lowers as much as 2 ft.