Exactly 50 years ago a momentous event in the history of road traffic took place. Sweden was the last major country to switch from left-hand traffic to right-hand traffic. That definitely had something to do with car lighting.

September 3, 1967 was a Sunday, just like in 2017. As usual at the weekend, most roads were quiet so traffic was flowing freely. Except in Sweden. From 1 o’clock in the morning most cars were banned from the roads. At 4.50 even the cars with special permits had to stop. Following a signal on the radio, they were only allowed to start again at 5 o’clock – but then on the right-hand side of the road. Sweden had switched from left-hand traffic to right-hand traffic, which was common in all its neighboring countries and in the whole of mainland Europe.

It was an unprecedented undertaking. Many thousands of intersections had to be converted. Traffic signs were moved to the other side of the road. Yellow road markings were changed to white so that road users were constantly reminded of the new rule, particularly in the countryside where traffic was quite light.

To this day, September 3, 1967 is called H Day, named after the first letter of the Swedish word “Hogertrafikomlaggningen”, which means switching to right-hand traffic. On that day traffic was restricted and only very limited speeds were permitted. Owners of private cars could use the day to remove two stickers from their vehicles. The stickers covered part of the headlights – the part which enhances dipped beam on the right side of the road. Swedes had to buy new headlights for right-hand traffic to prepare for this moment. Since about 1960 low beam has been asymmetrical, illuminating your own side of the road more than the opposite lane. From September 5, 1967 the old headlights for left-hand traffic would have dazzled oncoming traffic quite considerably. The new ones for right-hand traffic on the other hand would have been annoying for oncoming drivers in the weeks before the switch. That’s why the sections of the diffuser that are responsible for the asymmetrical part of the light distribution were covered. “Must not be removed before September 3, 1967”, it said on the opaque self-adhesive sticker.

Overall, the switch to right-hand traffic was still quite cheap. This was also the case for replacing the headlights. Only two round low-cost standard types fit almost all cars. Designers hadn’t gone crazy about lights yet and didn’t insist on each model having its own headlights. Today modifying some cars would mean a total loss.

There was one key feature that made the introduction of right-hand traffic a lot easier. Even during times of left-hand traffic, cars in Sweden always had the steering wheel on the left. That was because of the large market share of American cars which weren’t available as right-hand drives. And because getting out of the car by the curb seemed so convenient.

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