Category Description: 18-wheeler trailers that ran on the tracks themselves.
Trailer Train's TTAX All-purpose Spine Cars
Railroad Model Craftsman 1991-10 pg. 62 Scale: Author: Jim Panza
This article describes these cars in great detail. No modeling information is included, but there are lots of photos and many detailed scale drawings, as well as a roster list.
Triple Crown Services (TCS) Part 1
Model Railroading 2005-12 pg. 48 Scale: (none) Author: David G. Casdorph
Covers the 48-foot Roadrailers. Lots of close-up photos of the prototype.