If you live in the United States, you are very used to driving on the left side of the road. In fact, much of the world does, with the places that don’t being former British colonies.

But back then, it wasn’t always that way.

Many countries back then adopted driving on the right side of the road, but one particular example here is Sweden. Before 1967, Sweden drove on the left side of the road, though people didn’t like it because many people were coming into Sweden from Norway and Finland, and those countries used right-hand driving. It was also dangerous.

Even though in a 1955 referendum, 83% of people voted to keep LHT (left-hand traffic), the parliament of Sweden approved a proposal by the prime minister on May 10, 1963, which would officially make RHT (right-hand traffic) the norm nationwide on September 3, 1967.

A campaign called Dagen-H (short for Högertrafikomläggningen, very catchy) was set up to do nothing more than to remind people this day would come. They put up ads, road markings, merch with the logo of the campaign, including underwear and milk cartons, and even started a contest to see who could make the best Dagen-H song.

And so, September 3, 1967, came, and it was chaos. Don’t believe me? Take a look at Wikipedia’s cover image for the article:

Okay, okay, maybe it wasn’t that chaotic. They had a system: they banned all non-essential traffic from 1 AM to 6 AM, and any vehicles on the road at the time had to stop at 4:50 AM to change lanes, then continue at 5 AM. For the cities of Malmö and the capital of Stockholm, it was different: Non-essential traffic was banned from 10 AM Saturday until 3 PM Sunday. Some other cities did 3 PM Saturday to 3 PM Sunday.

The changeover seemed to work, actually; the number of accidents reduced, and the next day, they were lower, but by 1969, they were back to pre-Dagen-H. Railways and metro systems, which continued to drive on the left side, were abandoned and replaced by buses. A similar incident occurred on May 28, 1968, when Iceland changed to right-hand drive, on a day known as H-dagurinn.

This goes to show that changing a standard norm can have some bad long-term effects. It is still Sweden’s largest logistical event ever.

I just hope nothing like this changes in the US, or we’ll have a real problem…