BAKERSFIELD, Calif. (CN) — On a sunny early summer afternoon, I’m leaning over the wood railing at the Tehachapi Loop Overlook hoping for a train. Twenty minutes have passed, and I’m about to leave before I get sunburned when I hear a horn blast in the distance. Then another.
Several minutes later, a train pulled by three orange BNSF locomotives rounds the top bend of the loop.
To my surprise, another train emerges from the tunnel at the bottom of the loop at the same time. As the two trains near each other, the one coming down the loop comes to a stop and allows the one going up to pass.
“Wow, two trains at once,” my husband, who grew up in Tehachapi, says. “I don’t think I’ve seen that before.”
As one of the busiest rail corridors in the United States, seeing multiple trains on the Tehachapi Loop at once is actually quite common according to Daniel Cronquist, senior engineer with AECOM in Bakersfield and a fellow with the American Society of Civil Engineers.
Though Union Pacific owns the railroad after its acquisition deal with Southern Pacific was finalized in 1996, BNSF has trackage rights. Anywhere between 30 to 50 freight trains use it each day, with various sources listing various numbers.
Due to this heavy traffic, Union Pacific and BNSF teamed up with Caltrans in 2013 to improve the line with segments of double-tracking and improved siding. Completed in segments with and finally finished in 2020, the upgrades allow more — and longer — trains on the line.
The train that stopped on the loop to let the other train pass by was using this double-tracking. The choice of which train slows down to let the other pass depends on the railroad corporations, which factor in variables like cargo and scheduling demands to determine which train gets priority, Cronquist said in a phone interview.
Once the train going up the loop disappears behind the mountainside, the train going down continues on its way. Roughly 30 minutes later the last shipping container vanishes into the tunnel.
Built in the 1870s to connect the Central Valley and Southern California lines of the Southern Pacific Railroad Company, the roughly 3,800-foot Tehachapi Loop is the brainchild of civil engineer William Hood and his assistant engineer Arthur De Wint Foote.
The engineers knew they needed to go east from Bakersfield through the Tehachapi Mountains toward Mojave, but the difficult terrain and the need to make a steep rise in elevation at a grade the train engines of the time could manage posed significant problems.
Hood's solution was to design a loop. After exiting an approximately 430-foot tunnel, a train circles clockwise around a conical mound at the center of the loop, gaining 77 feet in elevation over a gradual incline at what Brett Hansen, writing for the American Society of Civil Engineers in a 2010 article, called a "steep but manageable" 2.2% grade. Any train longer than 3,800 feet — about 56 box cars — passes over itself going around the loop, always a thrill for trainspotters.
After its completion in 1876, the loop was the first of its kind in the world. Today it is considered "one of the seven wonders of the railroad world," according to the historical marker erected in 1953 when the loop was designated a California Historical Landmark. A little over 30 years later, the loop was designated a National Civil Engineering Historic Landmark in 1998 by the American Society of Civil Engineers (ASCE).
Though Hood and Foote typically get all the glory for this marvel of engineering, the loop and the Tehachapi Line itself would not exist without the blood and sweat of the roughly 3,000 Chinese workers who "cut through solid and decomposed granite using nothing more than picks, shovels, horse-drawn carts, and blasting powder,” the 1998 dedication plaque for the loop states.