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Dagen H: The Day Sweden Switched Traffic Sides (amusingplanet.com)
124 points by Clepsydra 11 days ago | hide | past | web | favorite | 81 comments

On most mining properties in North America and elsewhere, driving is strictly on the left. This is because haul trucks have such large blind spots to their right side, it's best to give them a clear view of the side of the road (which may be a sheer drop-off).

I've done a fair amount of driving on site, and it's a bit of a trip. Usually right after the main gate there is a cross-over point where you yield and switch sides. And don't forget to drive on the right after you leave for the day!


I heard somewhere that it used to be common in northern Italy to buy right hand drive cars (steering wheel on the right) for the same reason, it was better to have the driver at the edge of the road so that they could tell if they were too close to the edge on mountain roads with poorly defined edges and without crash barriers.

And the same in Sweden but the other way around - most cars had the steering wheel on the left even before driving on the right. Traditionally, it was better to be able to see where the narrow roads ended.

Interesting, I didn't know about the blind spot problem for trucks. Is there a reason we drive on the right in America, then? I kind of assumed we just randomly picked it because neither answer solves a problem with the alternative (or the country we copied randomly picked, I don't know the full history), but it seems like there's a pretty solid argument to always drive on the left (at least, there's no reason to drive on the right)

The fact that we drive on the right is the precise reason why trucks have less of a blind spot on the left. (We place the driver's seat closest to the center of the road, while on a mine site it's better to be close to the edge of the road.)

If we drove on the left and built cars accordingly, then you'd see mine site tricks driving on the right.

Left and right are not inherently different in any way (except I guess for people being right-handed more than left-handed, though has little effect.)

Fun story: I was surprised recently by visiting one country that did things a bit differently: Burma. They drive on the right and have for 50 or so years… but they use mostly left-hand drive cars. So you'll see the driver's seat close to the curb. Took me quite a few taxi rides to figure out what that uncanny feeling was. (Also, they're one of the few countries with a timezone offset by a half hour increment)

Burma is a fascinating story. They switched, like Sweden, but without planning.

The reason? A fortune teller said the country would be prosperous.

And now people exit the bus into the traffic instead of the sidewalk. Because nobody has the money to replace the buses or cars.

That is fascinanting. Can you provide a source for this story about a fortune teller?

They could switch sides of the road, instead of replacing the vehicles. Moving and rotating all the signs is probably cheaper and easier.

Replacing the vehicles is effectively free, if you do it slowly as you replace vehicles anyway.

> except I guess for people being right-handed more than left-handed, though has little effect.

Eye dominance is also a thing.

I'm from the UK so the steering wheel 'belongs' on the right hand side. However, I've driven thousands of miles across Europe and Canada.

The only time I ever struggled with driving on the other side (other than the occasional lapse while doing a U-turn on a very quiet street) was driving over the Alps in a manual hire car, driving a very narrow road with hundreds of switch-backs, where my weak hand (I'm right handed) wasn't used to the task of steering.

I can't say I've ever noticed any difference in vision.

If America drove on the left, the driver side would be on the right instead. This would only shift the truck blind spot to the other side meaning they would still drive opposite either way.

Why do you have to drive closer to the inside of the street?

Probably because you are routinely driving within a few feet of traffic coming the other way and it's easier to tell where the edge of your vehicle is when you're practically sitting on it versus sitting on the other side of the car.

So that you can see oncoming traffic when passing on a single/two-lane road

As the parent comment suggests, most people are right eye dominant so from a safety perspective keeping the dominant eye closer to the oncoming traffic is preferable. And even before cars, most right handed people mount horses from their right side, especially if they've a big sword on their left, and it is safer to mount from the side rather than the middle of the road. The story I learned when I was younger was that most of continental Europe, and the (at the time) pro-French US, shifted to the right because Napoleon was left handed, although it isn't quite that simple - see "Why do some countries drive on the left and others on the right?"[0].

[0] https://news.ycombinator.com/item?id=9869812 .

Edit: redundant

That’s discussed in the article

I talked to a guy at a gas station once with an exotic wrong way round car. He owned it because he was a car lover, but had come to prefer driving close to the kerb. He also enjoyed the lolz as other drivers did a double take when it appeared his dog was driving and he was the passenger.

These are special vehicles. Why aren't they built with the steering wheel on the right?

See also, the day the US changed its rail gauge: http://southern.railfan.net/ties/1966/66-8/gauge.html

I was in Sweden on the day they changed over. It was carefully planned. All of the signage was switched over night--old signs removed or covered and new ones revealed. I don't remember what was done for lane markings. Drivers had been practicing for months. Right-hand drive cars persisted for a while. Everything went surprisingly smoothly.

> I don't remember what was done for lane markings.

The Swedish Wikipedia article[0] mentions this. In conjunction with the change-over, lane markings went from yellow to white. This article doesn't mention it, but I recall reading that some roads had both colours during the transition.

0: https://sv.wikipedia.org/wiki/H%C3%B6gertrafikoml%C3%A4ggnin...

Thank you! Finally I get an explanation why in my youth some roads had yellow markings. I always thought the yellow markings was prettier.

A similar switch happened in 1970, when the Prime Minister of Myanmar suddenly and mysteriously decided that the country would switch to driving on the right-hand side of the road. The crazy thing is that the vast majority of vehicles today still have steering wheels on the right because the country has been buying used cars from Japan for years. Large vehicles like buses need a person acting as a spotter on the left side of the vehicle for safety! The Government finally mandated that, starting in 2017, imported vehicles must have steering wheels on the left side. Many drivers did not want to switch and thus there was a mad rush to buy cars in 2016, which the government was forced to counter by temporarily shutting-down imports.

Fascinating. For some interesting US history on the topic, see: https://www.fhwa.dot.gov/infrastructure/right.cfm

In particular I found this interesting: "[...] most American cars produced before 1910 were made with right-side driver seating, although intended for right-side driving [mirroring how horse-drawn carriages had been set up]. Such vehicles remained in common use until 1915, and the 1908 Model T was the first of Ford's cars to feature a left-side driving position."

Would be great to have - someday - everybody driving on the same side of the road. I wonder if space agencies have agreed to build space vehicles on a standardized side.

I moved from a country that drives on the right lane, to one in the Commonwealth, driving on the left lane. It's interesting the amount of adjusting it takes for you as pedestrian to get used to which side to make sure to look to before crossing, and as a driver (roundabouts are especially challenging in the beginning).

And not all cars here have the seats on the right side. You can find cars that were imported and have the driver seat on the left. Or old/classic cars too.

>>It's interesting the amount of adjusting it takes for you as pedestrian to get used to which side to make sure to look to before crossing

You should always look both ways regardless of which side a car is driving on. Reason is that bicycles sometimes drive in the opposite direction as cars. Also, sometimes cars, for whatever reason, will drive in reverse.

>You should always look both ways regardless of which side a car is driving on.

This is true, but when I finally went to a right-side country (Czechia) at age 29, I discovered that contrary to what I believed, I must not be, because I kept only looking right.

Concur. I believe that regardless of whether you look both ways or just one, if you're not expecting cars to be oncoming in a certain direction you're unlikely to see them.

When crossing two-way streets in countries that are opposite my own, I found it's trickier than it sounds due to some subtle subconscious thing even when you look both ways.

I think they're referring to places like roundabouts where you can cross halfway and the traffic only comes from one direction. Cars would never reverse off a roundabout and it's illegal and pretty dangerous to bike into a roundabout from the wrong direction.

The last percentage of risk is whether you bother checking for things that "can't" happen because "nobody would ever do that."

In primary school, we learned to look 'left, then right, then left again' before crossing. This is really muscle memory for me now.

That would have to be reversed in a country with left-side driving.

You are correct to worry about cars in reverse. I was nearly killed crossing the road when some idiot decided that going at 50km/hr in reverse up a one way street was a wise idea.

The order matters too and is different if people drive on the left or on the right

>> It's interesting the amount of adjusting it takes for you as pedestrian to get used to which side to make sure to look to before crossing, and as a driver (roundabouts are especially challenging in the beginning).

Agree, but I have to admit that I don’t have that issue anymore even if I change countries.

On the other hand I never remember that my native country has a strict policy on punishing jaywalking while UK doesn’t. It’s even harder to remember since the streets in the UK have way more traffic.

> I wonder if space agencies have agreed to build space vehicles on a standardized side.

Because space vehicles often need to share space roads?

Not generally, but note that the Mars Climate Orbiter[0] was lost due to an SAE-Metric conversion failure:

[0] https://spacemath.gsfc.nasa.gov/weekly/6Page53.pdf

What does that have to do with imaginary roads in space?

I would also not consider a planetary rover to be a “space vehicle”. Being on a planet is rather the opposite of space.

It makes me much more cautious crossing streets in London than in a typical US city. I simply don't trust my instincts about where traffic might be coming from.

I think self-driving cars will come sooner, in which case road handedness would be far less of an issue.

I can imagine a bad OTA update could someday result in some vehicles going rogue.

99% Invisible has a nice podcast on this:


Now I wish US can switch to the metric system with a similar endeavor, but surely it's impossible now.

There was an attempt in the 60s to convert to metric in US. If you are in SF bay area, go check this out:


That went into the 70s - when I was in school we learned both metric and imperial because the USA was in the process of switching. Wish we had followed through...

I don't think it is impossible, and many products wouldn't seem to change at all. 2L of milk visually looks like about a half gallon. (I am American and moved to Norway). Canned goods look to be around the same size. And so on.

Speed limits would take a bit of getting used to in some older cars, but I think most newer cars with digital dashboards would just switch over. Buying gas would take a little time, but it'll work out. A meter isn't all that different from a yard and rulers are cheap ways to measure centimeters. Signage and things will help folks do the conversion.

Temperature and distance, however, will take a bit longer. It has taken me a while to really understand how warm 10C is without having to convert the temperature, but I'm sure we can communicate such things. I still have no real handle on how far 100km is nor how long that would take to drive, though I know it is too far to walk.

Mostly, it would take legislation and money to start changing things (signs, for example) over. This would need to happen in 2 different stages so that for a decent time, both would be shown. Some things would just be immediately updated without issue.

Some of the sticker things probably needs to be funded as well - such as gas stations. I don't think they'd need to replace the entire pump, but it is a possibility especially for older stations.

Oh, and again, legislation needs to be there. In the current political climate, this is going to be a real hurdle and I can imagine it taking a patriotic tone much like the debate of teaching cursive writing.

> I think most newer cars with digital dashboards would just switch over.

I used to drive a 1986 Cadillac Eldorado which simply had a sliding switch to go from imperial to metric.

  There was an attempt in the 60s 
Late 70s, I think (Carter administration). I remember those. As a kid I wondered, "will they put in kilometer-marker signs like the mile-marker signs on state roads?" (the small white ones near road level).

It's inevitable that you will switch, you are just making it much more painful than it needs to be.

Did you notice that the SpaceX webcasts only use metric for the speed and altitude displays?

The only people that think it's painful are the folks who keep telling us we need to switch. We know the measurements we use pretty well, and even then there are plenty of things already measured in metric.

Plus, it's not like everyone else has fully switched. The UK still seems perfectly comfortable talking about weight in stones and all their cars measure speed in mph just like the US.

Yes nearly every country is in some sort of hybrid state. In Europe you have the UK with one foot in the empire, but other countries also mix in e.g inches for tv’s, car wheel sizes and so on. It’s almost not a measurement, it’s more like a size scale (you don’t measure your wheels in absolute terms but you know what 19” rims look like compared to 17”). Ironically we put mm sized tyres on these rims.

I think the US should try to switch one area at a time. Just like we will eventually measure Tv’s in metric (Australia does already I believe) the US could probably ease into metric by adding more and more areas that use it.

It's funny, as an Australian, TV's are probably the only think I know exclusively in inches.

At one point TVs were in centimetres and computer monitors were in inches, but now they've seem to have given up and sell both in inches (which is probably against some regulation somewhere).

I lived in Australia in 2002 and was surprised to see things like TVs be marketed in cm. Did that change? Makes sense to use the same marketing as manufacturers since model names will have inch sizes in them.

All screws here are metric, except for PC computer cases, harddrives etc. And screens, as mentioned. Everywhere the US influences global technology, the imperial units show up.

In the UK the metric system is used in business, construction, science etc. Really anything serious. Imperial measures seem to persist informally for things that are difficult to visualise, like body weight or speed. Or things that are customary like a pint. I will ask for a pint because that is how much beer I want to drink. Not because I actually care what unit it is in. And young people haven't got a clue how to add up pounds and ounces or inches and feet.

Ireland is 100% metric, yet you go into the grocery store and the butter is in 454g blocks.

That's because their main commercial partner (both because of geographical proximity and shared language which allows using the same packaging) isn't fully metric.

It used to be the same in Canada (or at least Québec) but I've heard that more products are sold in round metric quantities these days.

That's true for some sausages and jams, but all butter is sold in multiple of 250g in Britain.


Nearly all the butter you see here is labeled Irish, as is most of the other dairy and meat. The north has the opposite, most of the meat/dairy is labeled from NI. (With the exception of some of the branded stuff, like kerrygold butter which is available on both sides of the border. )

Even for TV size?

The US is already switching to metric by 1% per year.

The US military is metric (mostly).

The map in the article comes from (uncredited) the Wikipedia page 'Left- and right-hand traffic'. [0]

Btw, 35% of the world's population drive to the left, which is much larger than I thought.

0. https://en.wikipedia.org/wiki/Left-_and_right-hand_traffic

> 35% of the world's population drive to the left, which is much larger than I thought.

India would be a huge proportion of that.

There was a song at the time to help folks remember: “Håll dig till höger, Svensson” (Keep to the right, Svensson) [0]

[0]: https://youtu.be/6ODZtwkBYPs


>traffic accidents fell dramatically due to the extra caution people drove with

Feels like The Big Rewrite, but successful

Now UK and Japan can give it a try. ;-)

Not going to happen. UK and Japan are both island nations (as are Australia, New Zealand, and Indonesia), so there is no pressing need to change. And India is probably too large to change.

And Pakistan won't change because the camels wouldn't agree.

That's the story I heard, anyway. They were considering the change but then someone pointed out that the camel caravans continue through the night with the driver asleep on one of them and the camels know which side of the road they go on and if you tried to argue with them about it, well, they can be cantankerous, apparently.

That's hilarious. I wonder how traffic changes affect dogs and other animals that cross the road often?

Switching today would be virtually impossible. Just think of all the freeway interchanges that would have to be rebuilt, costing tens or hundreds of billions of dollars.

I think most interchanges would be fairly symmetrical. Although a lot of bellmouths at junctions would need to be changed to accommodate HGVs. And lanes approaching roundabouts would need to be moved.

Blame Napoleon

Of all things why does this keep getting posted here? Curious

It's an interesting question. A theory that occurs to me is that much of modern computing is the way it is due to network effects and historical baggage. We all fantasize of ways we could be doing things better, if only we could have a clean start. For us, the story of an entire country seamlessly jumping from a local optimum to a global one is practically pornographic.

See also: QWERTY keyboard

Debunked though?!

Interesting take, thanks.

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