Most of the world drives on the right side of the road. Sunday,
3 September 1967, Sweden went from left-side driving to right-side driving. And
it really did happen overnight. During the weeks leading up to “Högertrafikomläggningen”
(it means “right-hand traffic organization” and was eventually shortened to “Dagen
H” or “H Day”), every intersection in the country was equipped with signage and
traffic lights facing in the opposite direction. These were covered with black
plastic until H Day. All non-essential traffic was banned late Saturday night,
while workers roamed the streets, removing the plastic. Sweden made the switch
because Norway and Finland, with whom Sweden shares borders, both drive on the
right. Also, 90% of Sweden drove cars with steering wheels on the left, making
head-on collisions more likely on narrow, two-lane roads. Incidentally, the U.S.
used to drive on the left side, too. Our switch was much more gradual,
happening between 1792 and 1850.