Fiddling around on YouTube and looking at other videos linked to the Chevy on the FEC clip turned up this one.

http://www.youtube.com/watch?v=SxAqotcB_X8

I don't think this thing would really promote grade crossing safety, despite the comments at 0:45. Of note, though, is the older Rule 14L in effect at the time--two longs and two shorts, against the currently familiar two longs, a short, and a long we use today.

The problem that some railbus prototypes like this had was inadequate shunting, or completion of the track circuit between rails to activate signals, crossing signals, and the like. I'm willing to bet that was the issue with the crossing incident filmed here. The problem continued even with Budd RDCs, where rusty rail or an emergency stop on sand would break the circuit through the wheels and make single-car RDC runs not activate crossing circuits, or worse, disappear from signal circuits. The Pennsy-Reading Seashore Lines had to issue special instructions covering the operation of RDCs on rusty rail or making them pull forward after emergency stops as a result.

The Army tested a sort of locomotive version of this on the Claiborne and Polk Military Railroad in Louisiana during World War 2. Those of us who are interested in this operation have never seen a picture or any film, so if anyone out there knows about the Army tests, I would surely like to know about it, so that I can share it.