In Australia, is injury less in recent cars than in earlier cars? Evidence from comparing the injury severities of two drivers in the same collision.
Comparison of the severities of injury to the two drivers in the one collision is useful because speed of the impact is the same for the two drivers. Using the dataset of routinely-reported crashes in South Australia, 1991-2008, a multiple logistic regression was carried out, the dependent variable being the ratio of the probabilities of the drivers of car 2 and car 1 being killed, conditional on exactly one of them being killed. The independent variables were the difference between the two cars in their build years, the difference between the drivers’ ages, and an allowance for whether the vehicles fell within a narrow definition of car. Statistically significant effects were found for all of these. In a similar regression with the probabilities referring to the drivers being seriously injured, an effect of car year was again found.