“H Day”: The Night Sweden Switched to Driving on the Right

For much of the 20th century, a handful of European nations still drove on the left. Most of them made the switch to the right side early, when there were relatively few cars on the road, and the change went largely unnoticed. Sweden, however, waited until 1967—by then, in its largest cities, there were already more than 200 cars per 1,000 residents.

Fifty-eight years ago, on September 3, 1967, the country staged one of the most ambitious traffic experiments in history: “Dagen H,” or “H Day” (from höger, Swedish for “right”), when the nation shifted overnight to right-side driving.

Why Sweden Stayed Left for So Long

In the horse-and-carriage era, Sweden actually leaned toward right-hand travel—drivers would pass each other “left side to left side.” But when cars arrived, the country adopted left-hand traffic instead. By the late 1920s, the mismatch had become a problem, since all of Sweden’s neighbors—Denmark, Finland, and Norway—drove on the right.

Crossing the border could be dangerous. While major highways had crossover junctions to switch traffic from one side to the other, smaller crossings sometimes didn’t even have signs.

Drivers had to make the switch themselves—often with chaotic results. Dozens of accidents at the borders were reported each month.

The Swedish Road Paradox

By the mid-20th century, the situation was absurd: over 90% of the cars in Sweden had left-hand steering wheels—meant for right-side traffic—because most were imports, especially from the U.S. Even Swedish carmakers sold models with left-hand steering, since that’s what worked in neighboring Norway. Drivers simply got used to the awkwardness of sitting on the “wrong” side of their cars.

The Cost of Change

Between 1934 and 1954, Sweden’s parliament debated the switch at least seven times. Studies showed that converting the country’s entire road system would cost about $340 million—roughly half a billion in today’s money.

In a 1955 referendum, nearly 83% of Swedes voted against the switch. Still, by the early 1960s, the risks of left-hand driving with left-hand cars—especially during overtaking maneuvers—had become impossible to ignore. European institutions were also pushing for a unified standard. In 1963, the government set the date: Sweden would go right on September 3, 1967.

Unexpected Obstacles

The biggest challenges weren’t the cars—they were already suited for right-hand traffic—but the infrastructure. Every stoplight, road sign, highway exit, parking lot, and even roadside café had been designed for left-side driving.

Public transport posed an even greater problem. Swedish buses all had doors on the left, facing the curb. Most were retrofitted with new doors on the right; those that couldn’t be converted were sold abroad, many to Pakistan.

Preparing the Nation

The government launched a massive public awareness campaign. A pop song, “Keep to the Right, Svensson,” became a national hit and was played constantly on the radio. Schools, newspapers, TV, and driver’s ed programs all hammered home the message. Drivers even received mismatched gloves—red for the left hand, green for the right—to reinforce the habit.

By summer 1967, new road signs were in place, hidden under black covers until the big day. In August, Stockholm installed more new signs than it had previously had in total. Crosswalks were repainted, traffic lights reprogrammed, and road markings switched from yellow (as in the U.S.) to white, the European standard.

The Switch Itself

At 1 a.m. on September 3, traffic across Sweden came to a halt. Only emergency vehicles were allowed on the road. For five hours, workers uncovered new signs, repainted lanes, and reconfigured intersections—with the help of the Swedish army. In Stockholm, roads were closed for more than a day.

When traffic resumed at 6 a.m., police and traffic wardens directed cars through the unfamiliar new patterns. For the first few weeks, speed limits were lowered, and drivers were unusually cautious.

The Aftermath

Despite fears of chaos, “H Day” passed without a single fatal accident. Newspapers filled with photos of confused intersections and fender-benders, but most crashes were minor. In fact, accident rates fell sharply in the months immediately after the switch, as drivers remained on high alert.

Eventually, crash levels returned to normal—but Sweden no longer faced border problems, and traffic flowed more safely across Scandinavia. Trams switched to right-side traffic as well, though Sweden’s subways and railways still run on the left today.

A year later, in 1968, Iceland staged its own “H Day,” following Sweden’s lead.