rail line vs railway line

rail line and railway line both are nouns.

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

As nouns, rail line and railway line are synonyms defined as:

rail line and railway line: the road consisting of railroad track and roadbed

Other synonyms of rail line include line.

rail line (noun)	railway line (noun)
the road consisting of railroad track and roadbed	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