divided highway vs main road

divided highway and main road both are nouns.

Word	Noun	Adjective	Verb	Adverb
divided highway	Yes	No	No	No
main road	Yes	No	No	No

As nouns, main road is a hypernym of divided highway; that is, main road is a word with a broader meaning than divided highway:

divided highway: a highway divided down the middle by a barrier that separates traffic going in different directions
main road: a major road for any form of motor transport

Other hypernyms of divided highway include highway.

divided highway (noun)	main road (noun)
a highway divided down the middle by a barrier that separates traffic going in different directions	a major road for any form of motor transport