Until April 1972 Nigeria drove on the left, a colonial inheritance shared with Britain and most of West Africa under British rule. The economic argument for switching was the country's overland trade with francophone neighbours — Niger, Benin (then Dahomey), Cameroon, Chad — all of which drove on the right; the political argument was a post-civil-war modernisation push under the Gowon administration.
The Federal Government's 'Keep Right' campaign began in 1971 with a Federal Ministry of Works task force chaired by Brigadier Hassan Usman Katsina. Steel-and-paint road markings were lifted, traffic islands rebuilt, road signs reversed, and 'Keep Right' billboards installed on every federal highway. A nationwide radio jingle ran for six months. The changeover was timed for 00:01 on Sunday 2 April 1972; commercial traffic was banned from 06:00 Saturday until 06:00 Monday on most federal roads to allow the switch.
Nigeria's switch was the largest 'H-Day' (right-hand-drive day) operation in Africa after Sweden's 1967 changeover. It was completed without serious accidents on the changeover weekend. The cost — re-fitting Lagos buses, reversing the steering of military and police vehicles, replacing road signs and markings — was estimated at ₦3.5m at the time. The campaign is one of the few large logistical operations of the post-war Gowon era that worked exactly as planned.