island vs safety isle

island and safety isle both are nouns.

Word	Noun	Adjective	Verb	Adverb
island	Yes	No	No	No
safety isle	Yes	No	No	No

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

island: a zone or area resembling an island
safety isle: a curbed area in a roadway from which traffic is excluded; provides safe area for pedestrians

Other hyponyms of island include kitchen island, safety island, safety zone, traffic island.

island (noun)	safety isle (noun)
a zone or area resembling an island	a curbed area in a roadway from which traffic is excluded; provides safe area for pedestrians
a land mass (smaller than a continent) that is surrounded by water