Winding through the "Natural Crossover" at Frost, in the Victorville Narrows, is BNSF Railway train Z-NYCLAC7-18L. This Priority UPS-LTL Intermodal piggyback train is heading from New York NY to Los Angeles CA on December 20, 2014. For the BNSF leg of this journey, the power is BNSF ES44C4s 7113 and 6911 and Dash 9-44CWs 5512 and 4460.
In the days when this line was signaled as double-track, current-of-traffic (Rule 251), the line between San Bernardino and Frost, over Cajon Pass, was laid out for left-hand running so that eastbound trains used the easier gradients uphill from San Bernardino. Santa Fe built a “natural crossover” at Frost where the westbound line climbed up and over the eastbound line as the tracks curve from northeastward to northward. Because there is no longer a real need for the “natural crossover”, there is also a set of crossovers, with the usual signals, at Frost (MP 38.0), just at the north end of the ramp up to the crossover bridge. (Victorville, California)