On this day in 1967, Sweden changed what side of the road people drove on overnight.
Swedes had driven on the left since the 1700s, because that’s the side on which carriages were driven. But both countries bordering Sweden, Finland and Norway, drove on the right side. Plus, most cars in Sweden had the driver sitting on the left side of the vehicle.
Policymakers wanted a change, but the public vehemently rejected the idea in a 1955 referendum, with 82.9 percent of votes against reversing the direction of traffic. In 1963, Sweden’s government plowed forward anyway.
After months of preparation, workers finished up the switch in the early hours of Sept. 3, 1967, known as “Dagen Högertrafik” meaning “righthand traffic diversion day,” or (mercifully) “H Day” for short. For more on H Day, read the articles here and here.