railing vs safety rail

railing and safety rail both are nouns.

Word	Noun	Adjective	Verb	Adverb
railing	Yes	No	No	No
safety rail	Yes	No	No	No

As nouns, safety rail is a hyponym of railing; that is, safety rail is a word with a more specific, narrower meaning than railing:

Other hyponyms of railing include bar, fife rail, guardrail, taffrail.

railing (noun)	safety rail (noun)
a barrier consisting of a horizontal bar and supports	a railing placed alongside a stairway or road for safety
material for making rails or rails collectively