Recently, I’ve been wondering why in some countries we drive cars on the right side of the road while in others we drive them on the left. There must be a good reason for this difference in practice because it appears to achieve the same result just in a mirror image: when we travel on the right side of the road we drive from the left side of the car and when we travel on the left side of the road we drive from the right side of the car. Seems like a ‘tomato’, ‘tomahto’ kind of thing. So I looked it up. Here’s a brief outline of the history.
It’s important to note that the vast majority of humans are right hand dominant. This trend naturally determined common practices for traffic direction.
The earliest organized foot traffic kept to the left because it was safer to have your right hand closer to your passer-by so you could draw your weapon on them if you needed to.
Similarly, swordsmen wouldn’t want to bump scabbards with one another in passing; scabbards were worn on the left side because swords were drawn with the right hand.
Horseback traffic traffic adopted this practice of keeping left for the same reasons of weapon wielding and furthermore because horses were mounted/dismounted from the left side of the horse. It made good sense to be mounting and dismounting your horse on the side of the road rather than in the middle of the road. And so left-hand traffic was favored for this reason. Think about bicycles and motorcycles today - people generally mount from the left side so it seems it would feel safer to be in left-hand traffic on a bike, doesn’t it?
So LHT (Left-Hand Traffic) seemed to make the most sense and became a common practice throughout Europe and Asia. With the arrival of horse-drawn carriages, traffic became faster on large roads and so with main traffic (carriages as well as those on horseback) riding and driving on the left, people traveling on foot on these roads kept to the right to face oncoming traffic. It was safer to be able to see fast-approaching traffic and take avoiding action than to be run over from behind. This is a common-sense practice for slower traffic that is still observed today.
It wasn’t until the Napoleon Era of the French Colonial Empire that RHT (Right-Hand Traffic) was introduced. There was an obvious class distinction in France between the left and right-hand sides of the roads. The aristocrats drove in their carriages on the left hand side of the road, forcing the citizens who could only afford to walk over onto to the right. Come the revolution in 1789, the aristocrats had a natural incentive to keep to the poor side of the road, to avoid drawing attention to themselves. Traffic on the right became much more common and once Napoleon came to power, he ordered his military traffic to take the right side of the road. From all the sources I looked into, it’s clear that he did this but it is unclear why. I read in a few places that it may have been because Napoleon himself was left-handed and RHT would have favored him when he walked in traffic because he would wield his sword with his left hand and more easily face a potential opponent passing him on the left. Sounds pretentious of him. Regardless, the French observed RHT and then imposed this rule on the countries they conquered.
At this point there arose the divide in traffic direction with the British Empire continuing to impose the traditional LHT and the French imposing their new RHT.
The revolutionary wars and Napoleon’s subsequent conquests spread RHT to Germany, Italy, Poland, Spain, Switzerland, Belgium, Luxembourg, and the Netherlands. The British maintained LHT in their colonies namely India, the southern African countries, Australia and New Zealand.
There are some outlier countries with stories of their own (like Japan), but for the most part it was the influence of the British and French empires that shaped the choice between RHT and LHT going forward. The second link in the sources below goes to an article that goes into detail about situations in specific countries.
In America, the French colonized the southern states and the Canadian east coast. The Dutch colonized New Amsterdam (present-day New York). The Spanish and Portugese colonized the southern Americas. So The British were a minority in shaping the traffic. Furthermore, with the formation of the United States of America, RHT was eventually favored to cast off all remaining links with its British colonial past. The first law requiring drivers to keep right was passed in Pennsylvania in 1792, and similar laws were passed in New York in 1804 and New Jersey in 1813.
Once the USA drove on the right, LHT was ultimately doomed because the automobile industry in the USA produced good reliable vehicles that the rest of the world wanted and they were cars designed for RHT (steering wheel on the left side). So from then on many countries changed out of necessity depending on where they could reliably get their automobiles. For example, in September 2009, Samoa switched from RHT to LHT because it was easiest to get their automobiles from Japan and New Zealand who produced cars designed for LHT (steering wheel on the right side).
Some interesting research has been done to compare the safety of LHT vs. RHT. Research in 1969 by J. J. Leeming showed that countries driving on the left have a lower collision rate than countries driving on the right, It has been suggested that this is partly because humans are more commonly right-eye dominant than left-eye dominant. In LHT, the predominantly better-performing right eye is used to monitor oncoming traffic and the driver’s side mirror. Furthermore, in a right-hand drive car with manual transmission, the driver has the right hand, which for most people is dominant, on the steering wheel at all times and uses the left hand (and left foot) to change gears and operate most other controls.
So which method do you prefer? LHT or RHT? It’s always good to try new things and get out of your comfort zone. Find out which method works best for you. I am merely jesting about this. If you do this, you will place yourself in danger of head on collisions with opposing traffic.