A few times in the past week, I thought of the story I barely remembered about a country that switched which side of the road they drove on. It seemed unimaginable that an entire country could decide at a certain point in time to just change sides of the road. But a number of countries have done it. The one I was remembering was Sweden, which changed over on September 3, 1967.
Details are in the Changing from one side to the other section of the abundantly researched Which side of the road do they drive on? page. Another summary of who drives where and why is at Why Don't We Drive On The Same Side Of The Road Around The World?