Tehachapi Loop is an amazing feat of ingenuity to raise or lower a train a significant elevation in a very short distance. The project was completed in 1876, and has remained largely unchanged today.
When the train is going downhill, or generally to the northwest, it begins a descending arc in a clockwise direction. As it goes over a tunnel, it starts a 0.73-mile loop, tightening its spiral to encircle a hillock. As it completes the loop, 77 feet lower, the train circles under itself—through the tunnel that a long train might still be passing over. If the train is going uphill, or to the southeast, the process is reversed, with the engine entering through the tunnel, making the loop counter-clockwise.
If you don’t see a train immediately, have a little patience. An average of 36 trains per day use the loop.