Completed in 1876, the Tehachapi Loop enables trains to gain or loose 77 feet of elevation at a 2% grade along the spiral loop. Trains longer than 4,000 feet will pass over themselves at the tunnel, a distance of about 0.73 miles.
I waited for a couple of hours for a train to come by, but no luck. Another guy was there, umbrella for shade, camera on a tripod, a train buff and clearly a veteran at shooting trains there. He told me there as a some track maintenance going on that was limiting the number of trains per day that day, so I should try to come back another day.
I was on holiday, and didn't have the luxury of returning later, so I shot this image and went on my way.