Graphical tool for comparing ratios proposed in the literature on traffic accidents.

Investigators of accidents use accident rates and ratios to measure risk of being involved in a traffic accident. This paper uses two examples to present a graphical technique, that summarizes scatters of points by ellipses, to help describe the accident involvement of drivers. The first appendix tells how the technique works and the second appendix summarizes other types of ratios used in the literature. The paper discusses how the technique may tie together ratios in the literature on accidents and ageing of drivers.