railroad engineer vs engine driver

railroad engineer and engine driver both are nouns.

Word	Noun	Adjective	Verb	Adverb
railroad engineer	Yes	No	No	No
engine driver	Yes	No	No	No

As nouns, railroad engineer and engine driver are synonyms defined as:

railroad engineer and engine driver: the operator of a railway locomotive

Other synonyms of railroad engineer include engineer, locomotive engineer.

railroad engineer (noun)	engine driver (noun)
the operator of a railway locomotive	the operator of a railway locomotive