Article
Dagen H: the day 2 million Swedes started driving on the wrong side of the road — and accidents dropped
On September 3, 1967, Sweden did something no modern country had ever attempted: it switched from driving on the left side of the road to the right, nationwide, in a single morning. Within weeks, traffic accidents fell — not because people drove more carefully, but because they'd been driving the wrong cars for decades.
The problem that took 40 years to fix
Sweden had driven on the left since at least 1734, when the first ordinance on left-hand traffic was issued. A 1916 law reaffirmed it. By the 1950s, this put Sweden out of step with every neighboring country — Norway, Finland, and Denmark all drove on the right. Around 5 million vehicles crossed Sweden's borders annually, creating constant confusion at border crossings. [1]
The deeper problem was what Swedes drove. Most cars on Swedish roads were left-hand-drive vehicles (steering wheel on the left) — imported from continental Europe or built by Volvo and Saab for export markets. This meant the driver sat on the side closest to the center line. On narrow two-lane highways, overtaking required the driver to pull out into oncoming traffic blind, looking across the passenger seat. Head-on collisions were common. [1][2]
City buses were the opposite: right-hand-drive, with doors on the right — the correct configuration for left-side driving. But this meant bus drivers had the same blind-spot problem in the opposite direction. The whole system was a mismatch.
83% voted against it
In 1955, the government held a national referendum on switching to the right. The result was decisive: 83% voted to keep driving on the left. A violent scaremongering campaign had erupted about "the enormous waste of money the changeover would entail and, above all, the terrible bloodbath that would occur on the roads." [3]
But the numbers were moving against the status quo. Registered vehicles had shot up from 862,992 in 1955 to 1,976,248 by 1967. Road fatalities rose from 595 in 1950 to 1,313 in 1966. [2] On May 10, 1963, Prime Minister Tage Erlander's government pushed through a bill anyway, scheduling the switch for 1967. [1]
The four-year preparation
The Swedish Commission for the Introduction of Right-Hand Driving (Statens högertrafikkommission, or HTK) began a massive public information campaign. Every household received a 32-page pamphlet in up to nine languages. Television ran educational programs. A contest for songs about the change produced a hit: "Håll dig till höger, Svensson" ("Keep to the right, Svensson") reached number 5 on the Swedish charts and stayed in the top 10 for three weeks. [3]
The Dagen H logo — a leaning blue "H" on a yellow background — appeared on milk cartons, cups, socks, underwear, and bags. Children learned to look left through cartoons featuring Donald Duck and Dennis the Menace. [3]
On the infrastructure side, the work was staggering: approximately 360,000 street signs had to be replaced or relocated — 20,000 in Stockholm alone. Every intersection was equipped with an extra set of traffic signals wrapped in black plastic, to be unveiled on the day. A parallel set of road markings was painted in white and covered with black tape. Sweden's roads had previously used yellow lines. [1]
Vehicles needed their headlamps swapped from left-traffic to right-traffic units. One reason the government pushed ahead despite the unpopularity was that Swedish cars still used inexpensive, standard-size round headlamps — the trend toward expensive model-specific headlamps spreading through Europe would have made a later change far more costly to vehicle owners. [1]
The morning of the switch
Sunday, September 3, 1967. All non-essential traffic was banned from 1:00 AM to 6:00 AM. At 4:50 AM, every vehicle still on the road had to come to a complete stop. Drivers carefully changed to the right-hand side of the road, then stopped again — giving everyone time to reposition and avoid head-on collisions. At 5:00 AM, they were allowed to proceed. [1]
In Stockholm and Malmö, the ban lasted from 10:00 AM Saturday until 3:00 PM Sunday, giving work crews time to reconfigure intersections. Some 2,000 soldiers, 6,000 civil police, 50,000 school police, and 150,000 volunteers were on duty across the country. Construction workers labored through the night making final alterations. [4]
The Guardian's motoring correspondent, reporting from Stockholm that morning, described "cheering crowds" and "a solid jam" as sightseers and television crews swamped the roadway. "With military helicopters buzzing overhead, order was eventually restored," he wrote. Even the elk-hunting season had been brought forward a week so hunters wouldn't add to the traffic problem. [4]
The surprising result: accidents dropped
The doomsayers had predicted a bloodbath. Instead, the opposite happened. In the weeks following Dagen H, traffic accidents and fatalities dropped significantly. [1][5]
Why? Several factors converged. Strict speed limits were imposed alongside the switch: 40 km/h (25 mph) in built-up areas, 90 km/h (58 mph) on motorways. Drivers were advised to keep headlights on day and night. Everyone was hyper-vigilant, acutely aware that the rules had changed. [4]
But the deeper reason was structural. For years, Swedes had been driving left-hand-drive cars on the left side of the road — meaning the driver sat on the side closest to oncoming traffic, with a poor view when overtaking. Switching to right-side driving put the driver on the correct side for their left-hand-drive vehicle. The blind spot when overtaking on two-lane highways essentially disappeared. [2]
As one expert put it, "You would be sitting on the opposite side to what made sense… and you were looking down into the ditch." After Dagen H, they were looking at the road ahead. [2]
The effect didn't last forever — as drivers relaxed and returned to normal habits over the following months, accident rates gradually crept back toward pre-switch levels. But the immediate drop was real, and it demonstrated something counterintuitive: a massive, disruptive change in behavior, executed with meticulous planning, can produce a safer system than the one it replaced. [5]
Why it matters
Dagen H is often cited as a case study in logistics and behavior change — and it is. But the more interesting lesson is about alignment. Sweden's system was misaligned: the cars, the roads, and the rules were pulling in different directions. The switch didn't create a perfect system; it aligned the pieces that were already there. The accident drop was a one-time alignment dividend, not a permanent safety gain.
That pattern repeats everywhere. A system where the incentives, tools, and rules are mismatched produces worse outcomes than any one piece would predict. Aligning them — even through a disruptive change — can unlock a temporary but real improvement. The question is whether you seize the window.
Sources
- Wikipedia, "Dagen H" — https://en.wikipedia.org/wiki/Dagen_H
- BBC Worklife, "A 'thrilling' mission to get the Swedish to change overnight" (2018) — https://www.bbc.com/worklife/article/20180417-a-thrilling-mission-to-get-the-swedish-to-change-overnight
- Popular Science, "In 1967, 2 million Swedes started driving on the other side of the road" (2026) — https://www.popsci.com/technology/sweden-switch-sides-of-road/
- The Guardian, "Dagen H: the day Sweden switched to driving on the right – archive, 1967" (2022) — https://www.theguardian.com/world/2022/sep/07/dagen-h-sweden-switches-to-driving-on-the-right-1967
- Hagerty Media, "Dagen H: The day Sweden's drivers crossed a line" — https://www.hagerty.com/media/automotive-history/dagen-h-the-day-swedens-drivers-crossed-a-line/