The picture above is one of the rare instances when a camera is present for a singular, disruptive change in the order of things. Almost 50 years ago, Sweden braced for H-Day, the potentially catastrophic moment when everyone in the country started driving on the opposite side of the road. While the transition generally went smoothy, even the careful designs of Swedish planners couldn't prevent a few buckled corners.

Like the country's recent political drifting, the rightward change in traffic flow was driven largely by economic and border issues. At the time, Sweden was the only country in the vicinity with left-hand driving, creating traffic flow inconsistencies with neighbors Norway and Finland. Most Swedes drove left-hand drive vehicles like we have here in the States, making the original traffic arrangement a bit awkward as far as visibility.

In fact most cars driven in Sweden were American-made, but the market was still small enough that US manufacturers decided against making right-hand drive cars that would have been appropriate for the left-handed road rules. Instead, the rules changed and accommodated most cars already on the road.

Högertrafikomläggningen, as it's officially known (we'll just stick with H-Day), took place on September 3, 1967. Besides the obvious danger of people simply forgetting which side of the road they should drive on, planners had to deal with the tricky issues of one-way streets and the relocation of bus stops, not to mention the reversal of some 360,000 signs across the country.

Intersections had to be reconnoitered to allow traffic to merge. The morning of the change, all non-essential traffic was banned from the roads, in some places from 10 am that Saturday until 3 pm on Sunday. Any vehicles that were on the road had to come to a complete stop just before 5 am, and were then guided to the right-hand side of the road to stop again before they were allowed to proceed.

Sweden isn't the only country to switch sides, of course. As recently as 2009, Samoa made the left/right shift. The first officially established right-hand driving rule in the US was established in 1792, applying to the Philadelphia and Lancaster turnpike. Okinawa, while under US control, drove on the right until it reverted to the left in 1978, a few years after returning to Japanese sovereignty. In 1924, Canada, Poland and Spain switched to the right-hand side, and in 1928 Brazil and Portugal did the same. Austria made the switch gradually between 1919 and 1938. Britain, Ireland, Malta and Cyprus are the only European countries still sticking to the left.

H-Day (the "H" is for "Högertrafik," Swedish for "right-hand traffic") was actually the reversal of a 200-year-old driving regime, a left-side driving paradigm that held sway since 1734. It wasn't officially recognized as law until 1916, around the time cars started to become more commonplace.

Each year between 1920 and 1939 Swedish parliament argued whether they should make the switch to the scheme most of the continent was already using. Some think the long-standing lefty driving rule originated with the prevalence of right-handed swords. Whatever the reason, it was a relic from the age of horse carts and other pre-vehicle traffic. It was time for a change.

A nationwide referendum on the issue in 1955 generated fierce debate, with the proponents of change arguing the logical benefits of switching sides, while those who wanted a truly leftist Sweden appealed to tradition and emotion – perhaps not too dissimilar from the US's reluctance to convert from standard to metric measurement systems.

And like the US, the status quo was persistent, with 83 percent against against the change. Eventually though, Swedish parliament was swayed by extensive lobbying in 1963, and as part of the new order the Swedish National Traffic Safety Board was also established.

The monday after H Day, there were 125 non-fatal traffic accidents reported, down from the previous Monday average of 130 to 198. The drop was most likely due to risk-averse driving on what was anticipated to be a real carmageddon. So, while the number of motor insurance claims went down by 40%, over the next six weeks they returned to normal, and by 1969 the accident and fatality rates were back to their original levels.

Sweden's successful shift to the right was made possible through government hand-holding, with massive publicity and public education campaigns meant to prepare the population for at least a year in advance. Swedish TV even ran a songwriting contest to raise awareness. Just try not to tap your foot along to the winner (but not while driving, please).