I tried downloading some of Gunderson's content, but some of the dependencies were missing with a question mark: Unknown Location.
I found and successfully downloaded and added some non-articulated wellcars with yellow TTX/Trailer Train markings by josheh. Some were empty, some were double stacked and others had single container loads. These will still work great as a I have an industrial siding with an intermodal station, an animated workling container forklift by vulcan and some intermodal truck trailers by btvfd to use with my various Freightliner/Columbia/Classic/FL Day Cab tractors by yukonzoom and Kenworth tractors by willem2. Btvfd's intermodal container trailers aren't scaled well to any of the tractors as there is a big gap between the trailer kingpin (hitch) area and the fifth wheel plate on the tractors but they will do: they don't look too horrible at a distance. Washbash/Duraplate 53' trailers, and I have numerous models, by davesnow scale much better with my various author's tractor content. Thank's Dave!
Incidentally I just learned a new term: wellcar. When I had Googled 'intermodal railcar' to see if there was another name for them, the word wellcar was introduced and I was able to use 'wellcar' to find more intermodal train content via the DLS. I think the Brits and Aussies use a different type of car (or wagon) to handle container loads than does American roads. I once saw a video of some young boys who jumped trains for kicks like hobos. The wellcars with no floors unlike boxcars are very dangerous to ride on and the freight jumpers had to tie themselves firmly to the car's sides with belts or ropes or experience sudden violent death from falling into the menacing fast-moving rail ties below. Plus the open wellcars provide no shelter from harsh weather.