Monday, February 19, 2007

So that explains it

For all 5 years that I taught my sophomore tutorial, we discussed a JEP paper on the economics of convention. While the paper discusses various models for how conventions form and change, it is centered around which side of the road we drive on. If I recall correctly (and I'll look this up tomorrow when I can access the article), the author argues that you need need to have a driving convention because you don't want to have to stop and negotiate who is going to pass whom on which side everytime you come across someone going in the opposite direction. However, in his description, it was arbitrary which side was chosen. As long as enough people got the message to pass on the left (or right), that equilibrium would persist -- until either enough people in a row deviated convincing everyone else that the equilibrium had changed or until groups with different conventions started interacting with each other and forced convergence to a new equilibrium.

In almost every class, the "its arbitrary" explanation was unsatisfying. Students thought there should be a reason one side was preferred to the other. I never had an answer, so I just encouraged us to move forward. Now, however, I have discovered there may, in fact, be a reason for different driving convention. According to this website (which also includes a spiffy color-coded map of different driving regimes):

As one might gather from the map, the story of left or right hand side driving is more than just a derivative of British Imperialism. Right-handedness, a trait shared by 85 to 90% of people, is the reason for the initial preference for left and for the switch to right side driving.

Throughout the ages, horsemen preferred passing each other on the left side, because this allowed them to hold on to the reins with their left hand while with their right they shook hands with or swords at passers-by (as the situation warranted).

In the late 1700s, teamsters in many countries switched to bigger freight waggons drawn by multiple pairs of horses. They would sit on the left rear horse, thus able to whip with their right hand. This allowed them better vision on their left-hand side, so they preferred the opposing traffic to cross them on the left – meaning they switched to driving on the right-hand side of the road. So nowadays, an estimated 66% of people worldwide live in right-hand side countries, and 72% of all distances are completed while driving on the right side of the road.

Britain was the main exception: smaller waggons meant the driver was able to sit on top of them, not needing to ride one of the horses. British drivers remained seated on the right-hand side, and thus kept driving on the left-hand side of the road. This British custom would be adopted in most if not all British colonies, at least initially.

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