dual carriageway vs divided highway

dual carriageway and divided highway both are nouns.

Word	Noun	Adjective	Verb	Adverb
dual carriageway	Yes	No	No	No
divided highway	Yes	No	No	No

As nouns, dual carriageway and divided highway are synonyms defined as:

dual carriageway and divided highway: a highway divided down the middle by a barrier that separates traffic going in different directions

dual carriageway (noun)	divided highway (noun)
a highway divided down the middle by a barrier that separates traffic going in different directions	a highway divided down the middle by a barrier that separates traffic going in different directions