I think it might have been a stephen king based film. There is a late teen boy who see's the devil and evil things. He is trying to get to his mother across the country because she is dying. He hitches rides the whole way. His alternate self tries to tell him to pay attention to certain details (smells, sounds, daates, etc.) the rides include a hippie, trucker, and old man. The old man was already dead supposedly!

There is a scene after he leaves a graveyard where a dog (possibly shepard) attacks him but it was a pre vision/ then the dog gets hit by a car.

Its was weird and confusing but worth seeing again. He does make it to his mom but she died.

~ I think it's "Riding the Bullet"