Norfolk Southern closed down all but one of their RoadRailer corridors. The reasons include the age of the trailers and the lack of a builder for new ones or lack of enough business to justify building replacements.
The RailMate was a competing design using single-axle bogies (trucks) supporting the trailers. I've never seen photos/videos of them in revenue service beyond promotional material, but K-Line made O-Gauge models of them (I have four examples)
---PCJ