ring road vs highway

ring road and highway both are nouns.

Word	Noun	Adjective	Verb	Adverb
ring road	Yes	No	No	No
highway	Yes	No	No	No

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

ring road: a highway that encircles an urban area so that traffic does not have to pass through the center
highway: a major road for any form of motor transport

Other hypernyms of ring road include main road.

ring road (noun)	highway (noun)
a highway that encircles an urban area so that traffic does not have to pass through the center	a major road for any form of motor transport