491 just arrived in Farmington at sunset. Ahead of these guys is several hours of switching - most of it in the dark, then the hard long slog back to Durango - in the dark. These guys won't be home until after midnight.
If business was really heavy, an eastbound crew would be called as the train rolled northbound through Aztec. The eastbound crew (called about midnight) would go on duty, get their engines, caboose and the few eastbound cars in Durango Yard, then head down to Carbon Junction to await 491's arrival. The eastbound crew would take 491's train of empty pipe gons and empty dill mud boxes and head for Chama, arriving mid morning the next day..
The Narrow Gauge ran 24/7 back then.