On 3rd September 1967, Sweden changed their traffic rules. People now had to drive on the right-side instead of the left. The day is called Dagen H or Högertrafikomläggningen (“The right-hand traffic diversion”).
It resulted in chaos on many roads because the change was implemented overnight. The day is remembered for an iconic photo taken at Kungsgatan, Stockholm, which clearly shows the confusion on the road.
Image Source: By Jan Collsiöö, Public Domain, https://commons.wikimedia.org/w/index.php?curid=3713432
