scenic railway vs railway line

scenic railway and railway line both are nouns.

Word	Noun	Adjective	Verb	Adverb
scenic railway	Yes	No	No	No
railway line	Yes	No	No	No

As nouns, railway line is a hypernym of scenic railway; that is, railway line is a word with a broader meaning than scenic railway:

scenic railway: small railway in an amusement park
railway line: line that is the commercial organization responsible for operating a system of transportation for trains that pull passengers or freight

Other hypernyms of scenic railway include railroad, railroad line, railway, railway system.

scenic railway (noun)	railway line (noun)
small railway in an amusement park	the road consisting of railroad track and roadbed
	line that is the commercial organization responsible for operating a system of transportation for trains that pull passengers or freight