The Rio Grande Valley in December, where the air is cool, crisp, and clear. Looking geographically south toward Albuquerque, signal 8901 is a mere 10 miles from the city center, yet judging from the scenery there is no evidence of suburban sprawl. The reason? Signal 8901 is surrounded by the Sandia Indian Reservation, where agriculture is more important as a way of life than condominiums.

In the distance is signal 8902, which with signal 8901, shows the staggered pair layout of ABS overlap, where the extra quarter mile spacing would prevent a head-on in the event one train overlooked or misread a train order. Both trains would have approached their previous signals on a yellow,and would be prepared to stop at the next signal. In this case 8901 and 8902, which would be red. This staggered pair location is one of the few where both signals are visible from one spot. The Signal Department preferred to locate one signal at the top of a curve and the other at the bottom of a curve, so as to add additional protection to the curve. But in this stretch along the Rio Grande, there were no curves to offer.