Some countries drive on the left side of the road largely due to historical and cultural reasons dating back to times when people traveled on horseback. Knights and horse riders preferred to keep to the left so their dominant right hand was nearer to an approaching opponent for greeting or defense, and it was safer to mount horses from the left side (the curb side rather than the center). This tradition was maintained primarily in Britain, and when the British Empire expanded through colonization, many of its colonies adopted left-side driving as well. In contrast, much of continental Europe and other regions shifted to driving on the right side due to influences from Napoleon Bonaparte, who was left-handed and preferred right-side driving to keep his left hand free for sword use. France and the territories it influenced adopted driving on the right. The British remained driving on the left, and many of their former colonies still drive on the left today. Changing the side countries drive on is difficult and costly, so many countries stick with the system they inherited. Some countries like Japan drive on the left due to British influence on their early railways, though they were never colonized by Britain. Others have switched sides for practical reasons like regional conformity or vehicle import advantages. In summary, countries drive on the left mainly due to British colonial influence and longstanding traditions from horseback travel, while others drive on the right largely because of Napoleonic influence and subsequent continental European adoption. This split persists largely due to the logistical challenges of switching road systems and the legacy of historical choices.