police van vs police wagon

police van and police wagon both are nouns.

Word	Noun	Adjective	Verb	Adverb
police van	Yes	No	No	No
police wagon	Yes	No	No	No

As nouns, police van and police wagon are synonyms defined as:

Other synonyms of police van include black Maria, paddy wagon, patrol wagon, wagon.

police van (noun)	police wagon (noun)
van used by police to transport prisoners	van used by police to transport prisoners