The original Atlantic & Pacific line that eventually became the Atchison, Topeka & Santa Fe's Arizona mainline was built quickly and cheaply, as was pretty much standard with railroads in the American West in the nineteenth century. When the need for better grades and alignments became obvious over the ensuing years the Santa Fe often chose to add a second track on a better alignment rather than build entirely new double-track segments.
This location east of East Seligman, Arizona, provides a classic example. The westbound signals are the distant signals for East Seligman ahead; hence the double targets. The eastbound signals carry a round "G" placard below the lenses indicating that these are permissive signals not requiring a stop on red on the upgrade (but the engineer had better be ready to stop on a dime if necessary).
