State Route 99 Tunnel, Road tunnel in Downtown Seattle, US
The State Route 99 Tunnel is an underground road passage beneath Downtown Seattle that stretches 2 miles and provides four traffic lanes. It connects the SoDo neighborhood with South Lake Union by running under the city.
The project started after a 6.8 magnitude earthquake in 2001 damaged the Alaskan Way Viaduct. This event prompted extensive studies to find a better transportation solution for the city.
The tunnel boring machine was named after Bertha Knight Landes, Seattle's first female mayor from the 1920s. This choice became a way to honor a pioneering figure in the city's past.
Vehicles travel through the two levels of the tunnel, with traffic managed by modern control systems. Visitors should know that using the tunnel simplifies connections between the southern and northern parts of the city.
The construction required the world's largest tunnel boring machine, measuring 52 feet across. This giant machine worked for years to cut through rock and soil beneath the city.
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