The railroad from Alamosa to Durango and on down to Farmington was all built originally to standard gauge clearance specs. The Silverton Branch was not. That is why standard gauge equipment, ie the 490 series engines and MOW equipment like the rotaries clear. (The rotaries can not now go back to Antonito as the floor of Rock Tunnel was raise in the center to improve drainage and prevent ice build-up in the spring. This was done after the D&RGW sold the line.) BTW the newer C&TS coaches are built on standard gauge flat cars. The D&S opened up clearances and now the 490s can go to Silverton.