bilevel car vs railway car

bilevel car and railway car both are nouns.

Word	Noun	Adjective	Verb	Adverb
bilevel car	Yes	No	No	No
railway car	Yes	No	No	No

As nouns, railway car is a hypernym of bilevel car; that is, railway car is a word with a broader meaning than bilevel car:

bilevel car: a type of rail car that has two levels of passenger accommodation, as opposed to one, increasing passenger capacity.
railway car: a wheeled vehicle adapted to the rails of railroad

Other hypernyms of bilevel car include car, railcar, railroad car.

bilevel car (noun)	railway car (noun)
a type of rail car that has two levels of passenger accommodation, as opposed to one, increasing passenger capacity.	a wheeled vehicle adapted to the rails of railroad