The Rule of the Road, 1919-1986: A Case Study of Standards Change

In 1919, 104 of the world’s territories drove on the left and 104 on the right. Between 1919 and 1986, 34 of the keep-left territories changed to keep-right. No territories shifted in the opposite direction. This paper tests and largely sustains the counterintuitive hypothesis that the reason all changes were in one direction was less that there was any difference between keep-left and keep-right as rules, and more that the geographical position of many keep-left territories happened to put them under pressure to change from keep-right neighbors. This paper also discusses six other potential explanations of change, most of which played some role as well. Finally, it shows that the rule of the road is an example of standardization and convention. The explanations of change proposed for the rule of the road are familiar from many other cases of standardization.