Sound Transit planning floating light rail bridge

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SEATTLE — Sound Transit is planning a first for light rail transit in the U.S.: a floating rail line. Beginning June 3, the agency plans to begin building a light rail line on a floating bridge on the center express lanes of Interstate 90. Sound Transit has spent $53 million on designs for the bridge to ensure it stays buoyant when light rail trains roll across it. Service on the East Link between Seattle, Bellevue, and Overlake is scheduled to begin in 2023.

According to the agency, the biggest challenge was designing the rails so they would move with the bridge on Lake Washington, which rises and falls two feet in a year. Engineers designed the tracks so they will cross hinges and sloping spans between the bridge’s fixed sections and the one-mile floating deck. The design will help the rail bed resist and absorb roll, pitch and yaw, rather than fight forces of the trains.

The entire 14-mile corridor from Seattle to Overlake, including stations, trains and signal systems, is budgeted at $3.7 billion, but the Interstate 90 crossing will cost far less than building another bridge. The lake is considered too deep to install columns for a fixed bridge, and also too deep for a tunnel under the lake or along the lake bottom.

NEWSWIRETrains News Wire

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