Crossing Tunnel. Southern Railway SOU 4501 (2-8-2 "Mikado", Baldwin #37085, 10/1911) was a mere 104 years old on Sunday, August 2, 2015 when it crossed Tunnel Boulevard in Chattanooga, Tennessee. As part of the Norfolk Southern “21st Century Steam” program, the steam engine was rebuilt from 2011 to 2014 and used on numerous excursions. The locomotive was brought to the Kentucky & Tennessee Railway in 1948 and later to TVRM in 1961. On this day, it was making the usual run of the length of the Tennessee Valley Railroad Museum line from Grand Junction Station to the East Chattanooga Depot and Soule Shop through the Missionary Ridge Tunnel, but is also used by the museum for longer interstate trips.