"Cars" is a Greyhound term they used since forever for their bus/coaches. Drivers all used the term, and the dispatchers and management as well. Merely a Corporate Culture kind of thing. There was a touring company owned by Greyhound Corp. called California Parlor Car that ran up the coast road #1 along the cliffs, on the really scenic/scary portion, to Hearst Castle, Big Sur, Monterey etc. They used Greyhound drivers who were working Cal Parlor Car, as a separate company/division, still wholly owned by the Corp. They also only used 35ft Coaches (MC5) due to the winding nature of the road. I've driven that road on a few charters and it's truly one of the Sportiest drives around. I even took my J coach through the Devils Slide area once or twice and that was a real thrill for sure.Also it might help to remember the original GMC designation for the new model Rear engine Coaches starting with, I'm not sure(?), the P(arlor) G(as) G(??) 3751(?), as P(arlor car) D(iesel) XX(passenger capacity) XX(model number). PD 410X, PD4501, etc. They called them Parlor Cars and I guess Greyhound took it and ran with it.