British Columbia provincial highway 4, known locally as the Alberni Highway and the Pacific Rim Highway, is the longest east-west main vehicle route on Vancouver Island, with a total length of 163 km. The highway to Port Alberni was completed in 1942, and has been designated as Highway 4 since 1953.

Route details

Highway 4's eastern terminus is at an intersection with Highway 19A in Qualicum Beach, where the highway is known as Memorial Avenue. The highway starts off travelling due south for 2 km to an interchange with Highway 19. Another 2 km south of the interchange with Highway 19, Highway 4 meets a junction with an older Alberni Highway segment, now known as Highway 4A, at the small community of Coombs. Highway 4 veers directly west upon meeting this junction.

The majority of Highway 4's length is composed of a two_lane configuration. An abandoned spur of the E&N Railway parallels Highway 4 all the way from the coast to the city of Port Alberni.

West of Coombs, Highway 4 travels for 11 km before meeting the body of water known as Cameron Lake. After Highway 4 leaves Cameron Lake, it begins to wind its way through MacMillan Provincial Park, which includes the well-known area of Cathedral Grove. 20 km west of Cameron Lake, Highway 4 reaches a spur that travels into the city centre of Port Alberni. Highway 4 actually goes through land belonging to the city of Port Alberni starting 2 km west of the main spur into the city and lasting 5 km, after which Highway 4 finally leaves Port Alberni via a bridge over the Stamp River. The ensuing segment of highway from the Stamp River to the small community of Tofino on the west coast of the Island was opened to traffic in 1961.

6 km west of the Stamp River crossing, Highway 4 reaches the shore of Sproat Lake, following the lake shore west for 24 km. Highway 4 goes through Sutton Pass another 10 km later and turns toward the south-southwest. This bearing of Highway 4 continues for 23 km before reaching the southeast shore of Kennedy Lake. Highway 4 then follows the shore of Kennedy Lake southwest for 19 km, then reaches a junction with a spur into the settlement of Ucluelet 5 km later. At the Ucluelet junction, Highway 4 then makes a ninety_degree turn towards the northwest. 1 km later, Highway 4 enters the Long Beach arm of Pacific Rim National Park. Highway 4 goes through the national park for 22 km northwest, finally terminating 11 km later at Tofino.

British Columbia provincial highway 4A is the previous alignment of Highway 4 east of Coombs. The '4A' designation was originally assigned in 1968 to the current section of Highway 4 between Coombs and Qualicum Beach. The 4 and 4A alignments east and north of Coombs, respectively, switched designations when the Parksville to Mud Bay section of the Inland Island Highway was completed in 1996. This older spur of Highway 4 terminates in the east at Parksville, 10 km from Coombs.