Originally much longer than its present 100.8 km (62.6 mi) length, more than half of Highway 4 was transferred to the responsibility of local governments in 1998.

It travels along a short 2.7-kilometre (1.7 mi) concurrency with Highway 401 from the community of Tempo to Wonderland Road.

Wonderland Road is a 4-lane arterial thoroughfare serving western London, with several big-box stores, a mall, and residential areas.

[3][4][5] Highway 4 continues north, passing through Arva, when the surrounding terrain returns to farmland.

The highway then curves slightly west, passing through Lucan before continuing north at Clandeboye.

Two months later, on May 11, it was extended south to Bedford Street (now Edith Cavell Boulevard) in Port Stanley.

[12][13][14] As part of a series of budget cuts initiated by premier Mike Harris under his Common Sense Revolution platform in 1995, numerous highways deemed to no longer be of significance to the provincial network were decommissioned and responsibility for the routes transferred to a lower level of government, a process referred to as downloading.