bilevel car vs double-deck railcar

bilevel car and double-deck railcar both are nouns.

Word	Noun	Adjective	Verb	Adverb
bilevel car	Yes	No	No	No
double-deck railcar	Yes	No	No	No

As nouns, bilevel car and double-deck railcar are synonyms defined as:

bilevel car and double-deck railcar: a type of rail car that has two levels of passenger accommodation, as opposed to one, increasing passenger capacity.

Other synonyms of bilevel car include bilevel rail car, bilevel railcar, double-deck carriage, double-deck rail car.

bilevel car (noun)	double-deck railcar (noun)
a type of rail car that has two levels of passenger accommodation, as opposed to one, increasing passenger capacity.	a type of rail car that has two levels of passenger accommodation, as opposed to one, increasing passenger capacity.