nonsmoking car vs passenger car

nonsmoking car and passenger car both are nouns.

Word	Noun	Adjective	Verb	Adverb
nonsmoking car	Yes	No	No	No
passenger car	Yes	No	No	No

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

nonsmoking car: a passenger car for passengers who want to avoid tobacco smoke
passenger car: a railcar where passengers ride

Other hypernyms of nonsmoking car include carriage, coach.

nonsmoking car (noun)	passenger car (noun)
a passenger car for passengers who want to avoid tobacco smoke	a railcar where passengers ride