double-deck carriage vs bilevel railcar

double-deck carriage and bilevel railcar both are nouns.

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

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

double-deck carriage 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 carriage include bilevel car, bilevel rail car, double-deck rail car, double-deck railcar.

double-deck carriage (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.