Research in 1969 by J. J. Leeming showed countries driving on the left have a lower collision rate than countries driving on the right. This research is questioned in Peter Kincaid's book on the rule of the road,[citation needed] but some countries that have switched to driving on the right, such as Sweden), have seen their long-term accident rates increase by more than any increase in traffic volume[citation needed]. It has been suggested, but not proven, that this is partly because it is more common to be right-eye dominant.[12][13][14] Traffic flows in a clockwise direction when driving on the left which enables right eyed people to use the right eye to see oncoming traffic. When overtaking (passing) on a right-side-driving road, the right-eyed driver looks in the wing mirror (side mirror) with the left eye and also views the oncoming traffic with the left eye which is not suited to the majority right-eyed people.