trunk route vs trunk line

trunk route and trunk line both are nouns.

Word	Noun	Adjective	Verb	Adverb
trunk route	Yes	No	No	No
trunk line	Yes	No	No	No

As nouns, trunk route and trunk line are synonyms defined as:

trunk route (noun)	trunk line (noun)
line that is the main route on a railway	a telephone line connecting two exchanges directly
	line that is the main route on a railway