Oh OK, well glad you are interested.
I sort of thought everyone who was interested in trains knew something about it (actually I am not a massive puff puff buff, or train enthusiast myself, but one of my mates is (full on), and that is how I know about it).
The Tehachapi Loop is a 0.73-mile (1.17 km) long spiral, or helix, on the Union Pacific Railroad Mojave Subdivision through Tehachapi Pass, of the Tehachapi Mountains in Kern County, south-central California. The line connects Bakersfield and the San Joaquin Valley to Mojave in the Mojave Desert. The line, which sees an average of almost 40 trains each day, is one of the busiest single-track mainlines in the world. One of the engineering feats of its day, the Loop was built by Southern Pacific Railroad to ease the grade over Tehachapi Pass. Construction began in 1874, and the line opened in 1876. Rising at a steady 2% grade, the track gains 77 feet (23 m) in elevation in the Loop. A train more than 4,000 feet (1,200 m) long passes over itself going around the loop.
Opened in Sept 2016, second track sections were added to help improve train traffic flow.
