On this date in 1967, after years of resistance, Sweden experienced the unpopular "H DAY" - still known as Högertrafikomläggningen" ("The right-hand traffic diversion") - when traffic switched from driving on the left side of the road to the right. Psychologists recommended a 4-year campaign to promote it, which even included "Dagen H" commemorative underwear and a song contest (the winner was Håll dig till höger, Svensson - "Keep to the right, Svensson" by The Telstars).

See the Swedish info-film at http://tinyurl.com/nqv5ckl