I wonder if BeaNSnifF still uses them on the end of intermodal doublestackers in a trailing position.
I’ve seen well cars with doublestackers, trinity spines, and 85’ or 89’ flatcars mixed in from time to time.
I think you see less TOFC because foreign made products are brought over in containers.
Sure, if you can stack two containers then you can carry more of them. The RR’s recognized that over 40 years ago and began designing well cars which could carry two containers stacked. In 1977 SP & ACF developed the first double stack car which began the revolution.
http://www.railgoat.railfan.net/spcars/byclass/flat/f070-81.htm
Prior to that there were containers being carried on flat cars, COFC. That practice continued for a long time, but efficiencies caused them to be fewer and fewer over time.
And yet in much of the North East and Mid Atlantic well cars run with only one container because of bridge and tunnel clearances too expensive to increase.
Sheldon
There is also a lot of purely domestic intermodal traffic. International container ships are largely set up for 20’ and 40’ ISO containers. 53’ high-cube containers are pretty much North American domestic only. (There may be a few limited exceptions.)