in front vs ahead

in front is not an adjective while ahead is an adjective.

Word	Noun	Adjective	Verb	Adverb
in front	No	No	No	Yes
ahead	No	Yes	No	Yes

As adverbs, in front and ahead are synonyms defined as:

Other synonyms of in front include before.

in front (adjective)	ahead (adjective)
	having the leading position or higher score in a contest

in front (adverb)	ahead (adverb)
at or in the front	at or in the front
	ahead of time; in anticipation
	in a forward direction
	leading or ahead in a competition
	to a different or a more advanced time (meaning advanced either toward the present or toward the future)
	to a more advanced or advantageous position
	toward the future; forward in time