There is something truly satisfying about catching two (or more) moving trains in one photograph. Pictured climbing former D&RGW rails, two eastbound UP trains head through CP RG685 Castilla in Spanish Fork Canyon. The UP 5723 is leading an MRONY, Salt Lake City, UT to Denver, CO manifest while the UP 7028 leads a Long Beach, CA to Savage, UT coal empty. The manifest departed Ironton (near Provo) about 5 minutes ahead of the coal empty. Since main 2 is about a mile longer (and the train is heavier) the coal empty was able to catch up with and overtake the manifest by the east portal of the Thistle Tunnels. This is a good example of the flexibility of CTC and two main tracks. The D&RGW knew this and invested wisely in the technology many decades ago. Today UP dispatcher 78 is the benefactor of this flexibility, although there is far less train traffic along these rails for which to utilize it's potential.
