Seasonal Variations in the Age-Related Collision Risk of Ontario Drivers

Studies of age-related collision risk have not considered how collision risk varies by season. In 1994, the Ministry of Transportation of Ontario conducted an exposure survey which gathered year-round data to ensure that seasonal variations in collision risk could be measured and analyzed. Three-day trip logs were mailed to a stratified random sample of 11,250 Ontario drivers. The logs were mailed out at the rate of 938 per month. The survey was conducted from December 1993 to November 1994. The mean daily kilometrage for six age groups was estimated, and seasonal collision rates per 1 million km driven were calculated. Drivers aged 80 to 89 show the most dramatic fluctuations in collision risk. The winter collision rate of 22.4 is over three times higher than the rate observed in the fall (6.7). The collision rate in spring (13.4) is twice that observed in the summer and fall. When the youngest and oldest age groups are compared, it is evident that the collision risk of 80- to 89-year-old drivers is 2.0 times higher in winter and about 1.5 times in spring. The youngest drivers, however, have a collision risk that is substantially higher than the oldest drivers in summer and fall.