The number of elderly drivers has been increasing in Japan with the rapid progress of the nation's population aging. Securing safety for elderly drivers is an important issue in Japan. In this paper, authors conduct analysis on characteristics of accidents and violations caused by elderly drivers based on data for 2009. As there is a tendency that elderly drivers generally have less opportunity to drive vehicles than younger drivers do, it is necessary to conduct this analysis considering driving frequency when making comparison among age groups. Then, we calculated the normalized ratio (odds ratio) based on the number of rear-ended accidents in order to exclude the influence of driving frequency. As a result of the analysis, it was found that the likelihood of violations committed by elderly drivers was not particularly higher, while the likelihood of accidents caused by them was higher than younger drivers. The risk of causing an accident was judged to be about two times higher in elderly drivers than in the 35-44 year age group. Looking at each type of accident and violation, it is conjectured that they do not purposely disregard traffic signals or commit stop sign violations, but end up having accidents as a result of simply failing to notice them.
