roadway vs carriageway

roadway and carriageway both are nouns.

Word	Noun	Adjective	Verb	Adverb
roadway	Yes	No	No	No
carriageway	Yes	No	No	No

As nouns, carriageway is a hyponym of roadway; that is, carriageway is a word with a more specific, narrower meaning than roadway:

roadway: a road (especially that part of a road) over which vehicles travel
carriageway: one of the two sides of a motorway where traffic travels in one direction only usually in two or three lanes

roadway (noun)	carriageway (noun)
a road (especially that part of a road) over which vehicles travel	one of the two sides of a motorway where traffic travels in one direction only usually in two or three lanes