A World-Famous Railroad Construction Achievement of the 19th Century
Located about eight miles west of Tehachapi, California, near Highway 58
In the 1870's the Southern Pacific (Central Pacific) Railroad sought to link their rails in central California to those in Southern California. The path was blocked by the rugged Tehachapi Mountain range, which acts as an east-west barrier between Bakersfield and Los Angeles. Since construction directly south was impractical, the Southern Pacific Railroad decided to go southeast to Mojave, through the Tehachapi Pass. The summit at Tehachapi Pass was 4000'. Construction from Bakersfield to Caliente was somewhat routine, but from that point on the elevation going east rises quickly. From Caliente to the summit (now the City of Tehachapi) the rise is 2,735 feet. The maximum grade permitted was 2.2%. By routing the track alongside the slopes of the Tehachapi foothills, engineer William Hood could envision completing the task. However, just east of Keene, there was an apparently unsolvable problem. An increase in elevation of nearly 80 feet was required, unattainable using typical designs .
The problem was solved by constructing a unique loop. Going southeasterly from Keene, a train first passes through an entry tunnel. The track then does a complete counterclockwise loop, passing over the entry tunnel before continuing easterly. (See sketch below). The loop is sized to have a length adequate to achieve the needed gain in elevation. The result is a loop 3,799' long, with a typical diameter of about 1210 feet. By continuing to gain elevation throughout the loop, engineer Hood was able to make up the needed elevation (about 77' rise in the loop). With modern freight trains, often more than a mile long, the locomotive passes over (or under, depending upon direction) the final cars of its own train!