trial run vs road test

trial run and road test both are nouns.

Word	Noun	Adjective	Verb	Adverb
trial run	Yes	No	No	No
road test	Yes	No	No	No

As nouns, road test is a hyponym of trial run; that is, road test is a word with a more specific, narrower meaning than trial run:

Other hyponyms of trial run include field test, field trial, alpha test, beta test, trial balloon.

trial run (noun)	road test (noun)
trying something to find out about it	a test to insure that a vehicle is roadworthy