Most of us are familiar with the re-gauging of the D&RGW Monarch Branch in 1955 and how it continued in operation until the mines played out. Did Rio Grande ever seriously consider re-gauging or dieselizing the narrow-gauge network from Alamosa? An EMD GA8 or GA12 in Rio Grande colors would be most interesting.
Or an Alco/MLW DL-535E like White Pass & Yukon operates…
They looked at it more than once, regauged what made sense, ran what they could. From the 1930’s on, the taxpayer subsidized trucking industries did-in the intermountain ltl/lcl business of the narrow gage network. (Monarch Branch was hardly the only line regaged by D&RG/D&RGW). A lot of what was re-gauged shrivelled-up anyhow.
The geometry and the bridges in places made regauging costs prohibititive. There wasn’t that much traffic to start with. (The narrow gauge lines that survive often do because the unique nature of the beast is so impressive and would have been cost prohibitive to regauge).
DRGW had a handful of NG diesel mice as it was.
A couple of the books by the late John Norwood (Rio Grande Narrow Gauge and Rio Grande Narrow Gauge Recollections) mentions plans over the years for regauging, and new alignments in some cases. I forget off hand which book, but one plan included a tunnel on Cumbres Pass with a new alignment.
There are also a few pictures of a U.S. Army diesel-electric being tested in the early 1960s.
Had some of the early plans actually happened, maybe (big maybe) some of those lines may have survived. However, I think a lot of the charm that made them interesting, and viable for what we have today as tourist operations, would’ve been lost.
Jeff