Just after lunch in Fowler, Colorado -- Mexican food, and good! -- we’ve come upon RSD 2159 just setting out for La Junta with a rattletrap collection of work cars. We poke alongside, shooting out the windows when the 2159 begins to accelerate….to 40, to 45, to 50. At 65 we’re forced to abandon the chase on this two-lane highway and the 2159 pulls ahead. We wonder: Can an RSD5 run that fast? What’s the permitted speed for a work train on this line, which sees some of Santa Fe’s fastest passenger runs? It’s an impressive performance by a 10-year-old road switcher headed for retirement.