One of the technologies that enables the Union Pacific to carry such a formidable flow of traffic over an obstacle like Sherman Hill on just two tracks is CTC (Centralized Traffic Control) with its associated bi-directional signaling. These signals seen at Otto also feature the "Darth Vader" shields in use on both the Union Pacific and Denver & Rio Grande Western long before they became a fixture in the east.
Incidentally. did you notice the distant freight on the Harriman Cutoff at right?
