Starting in 1928 with Portugal, close to 40 countries have changed the side of the road traffic drives on.  There have been several reasons countries have switched sides, mostly to conform with neighbors, as it increases safety at borders, but also due to new colonial governments (Taiwan switched when China took over in 1946) or freedom from colonial powers, like in the case of Gambia, Nigeria and others.  One of the most interesting reasons to switch sides was given by Burma, in 1970, when on the advice of a wizard the Burmese switched from left to right.   Burma may have used unorthodox logic (or lack there of) to justify their switch, but they were keeping with the logical tradition of joining the majority of the world on the right side of the road.  Only Mozambique has switched from the right side of the road to the left, due to the fact that the majority of their neighbors including South Africa,  drive on the left, however their old colonial overloads (the Portuguese)  switched to the right back in the 20’s so Mozambique was one confused country.   

Now another country is bucking the trend, becoming confused and joining the minority, and its not doing this due to transnational boundaries- it doesn’t have any.  It’s not doing it for safety reasons, all logic indicates this move will be quite dangerous, actually.  In fact based on what information is available the decision to switch sides was based on very little information at all, making Samoa more like Burma in the way this decision was made. 

Check out the great map from Wikipedia for an illustration.

About 66% of the worlds population drives on the right hand side of the road.  On the map below  red represents right hand side and blue .. well those are the left handers.