Highway 4 starts at an intersection with Highway 19A in Qualicum Beach, and immediately heads south 2km to an interchange with Highway 19. Just south of this, the highway meets a junction with Highway 4A in Coombs. The highway travels west from here to Cameron Lake. It travels along the shore of Cameron Lake for about 5km, then goes through MacMillan Provincial Park to Port Alberni. I exits Port Alberni to the west, crossing over the Somass River.