Every time I use the London Underground the same thought occurs to me - on the escalators, why do people always overtake on the left?
Why does everyone follow the same rule? How did this rule come into being? On British roads overtaking is done to the right, so why it is different on the Tube?
Rules like this are often called social conventions, or norms. Economists have long been interested in how they come about and what sustains them. Hopefully this will shed some light on the matter.
On escalators there are three possible social conventions. Firstly, overtaking is done to the left. Secondly, overtaking is done to the right. Thirdly, people can stand wherever they wish; overtakers have to weave their way through.
Clearly the third option is inefficient; slowing down the people in a rush. Thus there is a clear advantage to the first two options. However, they are equally efficient; there is no particular advantage to choosing one over the other. So why is the first one in operation?
Once a convention is in place it is easy to see how it will be self-sustaining: one does not benefit by deviating from the rule. But how did the rule come to be chosen in the first place?
It's important to remember that social conventions are not created by everyone sitting down and having a good old chin-wag about what would be most efficient. Rather, they're formed by many individuals doing that which they think (or guess) will benefit them the most in any given context.
The economist Robert Sugden points out that social conventions are often borrowed from other contexts. When it comes to guessing what one should do in a particular situation, we may follow a rule that we've seen working in a different situation. Thus the ease of transferability of a convention is important. But it is not obvious why overtaking on the left is more easily transferred from other contexts.
So I did some detective work...
According to Wikipedia, people were originally told to overtake on the left because the original escalator design made it marginally faster to be on the left hand side: if you were in a rush the left was the place to be. If I'm honest, I can't understand how one side could get you to there faster, but then I'm just a simple economist.
Devastatingly, Wikipedia implies that the overtake on the left rule was introduced by the authorities. If so, it is less of a social convention and more of a top-down law. Luckily, it's only Wikipedia.
Anyway, I hope this thought experiment has been interesting. Please do suggest any alternative explanations for why we overtake on the left...
Recommended listening:
Baker Street by Gerry Rafferty
Going back to medieval times and the invention of spiral staircases, they always have an anticlockwise rotation when viewed from above. (in those times, everyone was right handed) This meant that if a castle was invaded, the defenders coming down the tower would have the advantage of their sword carrying hand been on the wide side of the stairs ready to swing down on the attacker whilst the attackers right arm was restricted by the tight curve of the spiral.
ReplyDeleteExtrapolating this forward several decades, we now have a more equal share of lefties and righties but old habits die hard and I presume many people still keep their dominent (right) hand free, carrying luggage in the left hand. Therefore when approaching an escalator it would be more natural to stand on the right side with your free hand next to the handrail. This would then leave the left side free for overtakers who use the handrail less, carry less luggage and wouldn't mind switching anything they were carrying to their right hand to gain a performance boost.
Indeed it would be interesting to research whether their is correlation between people who regular overtake on escalators and people who carry their bag in their right hand. I could show an evolution of the overtaker to be for adept at using a left side handrail.
Hmmm...maybe it could be something to do with the signs that say keep-left...just a thought?
ReplyDelete