Between the city of Whittier and Alaska's interior looms Maynard Mountain, known for subzero, 150-mph winds, but, thanks to engineers, the port has vital highway access to the other side.
Rather than go over, around, or blast a way through, they modified a railroad tunnel for use by motor vehicles.
At 2.5 mi., the Anton Anderson Memorial Tunnel is North America's longest dual-use tunnel.
Because it's only one-lane wide, computers control the direction of traffic and prevent vehicles from being inside at the same time as a train. Jet engine fans help clean the tunnel's air, and the entryways are specially built to withstand avalanches.