I came across this film about the RDC this evening. I found it interesting. I can't help but wonder, if the railroads were able to convert most of their passenger trains to RDCs, would they have fared better, financially.
As you can see in the film, they were and are very versatile. A single train can be split in two at a point where two final destinations were required. There would not be a need for locomotive changes as each unit is self propelled.
Along with baggage/mail RDCs, I am sure diners, sleepers, lounge cars and every other type of passenger car could have been made using RDCs.
Maybe just wishful thinking on my part, but wouldn't it have been good for the railroads to have survived on an individual basis.