Sweden’s 1967 nationwide switch from left-hand to right-hand traffic was called Dagen H.
The Swedish phrase högertrafik means “right-hand traffic,” and the H in Dagen H refers to höger. The change occurred on 3 September 1967 after a major national preparation campaign. Sweden had driven on the left, but its surrounding countries used right-hand traffic, creating complications at international borders and for imported vehicles.
The switch required new road markings, redesigned junctions, altered bus doors, and large-scale public education. On the morning of the change, traffic was stopped so vehicles could move to the correct side under controlled conditions. The operation was implemented across the country rather than gradually by region.
Dagen H is sometimes confused with Sweden’s decision to change its road side, but the terms describe the same event from different angles: högertrafik names the new system, while Dagen H names the changeover day. Sweden has used right-hand traffic ever since.