railroad car vs wheeled vehicle

railroad car and wheeled vehicle both are nouns.

Word	Noun	Adjective	Verb	Adverb
railroad car	Yes	No	No	No
wheeled vehicle	Yes	No	No	No

As nouns, wheeled vehicle is a hypernym of railroad car; that is, wheeled vehicle is a word with a broader meaning than railroad car:

railroad car: a wheeled vehicle adapted to the rails of railroad
wheeled vehicle: a vehicle that moves on wheels and usually has a container for transporting things or people

railroad car (noun)	wheeled vehicle (noun)
a wheeled vehicle adapted to the rails of railroad	a vehicle that moves on wheels and usually has a container for transporting things or people