double-deck railcar vs bilevel railcar

double-deck railcar and bilevel railcar both are nouns.

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

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

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

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

double-deck railcar (noun)	bilevel 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.