Comparison of automated vehicle struck-from-behind crash rates with national rates using naturalistic data.

Automated vehicle developers in California are required to submit records of crashes and distances traveled in autonomous mode for all vehicles in their fleets. Several studies have investigated this database to compare automated vehicle crash rates with national rates. Although automated vehicles are struck from behind in 73 % of their autonomous mode crashes, this is the first study to compare automated vehicle struck-from-behind crash rates to national rates using equivalent crash definitions. Rear-end collisions have substantial public health and economic impacts, representing a third of all collisions and $3.9 B in annual economic costs. In this study, automated vehicles in autonomous mode were found to be struck from behind at 4.8 times the rate of human-driven vehicles in a naturalistic driving study. When controlling for driving environment, the rates for AVs were 5.0 times higher for urban driving and not significant for business/industrial driving, although these results are for different manufacturers, complicating the results. Automated vehicles were more likely to be struck when stopped than when moving compared to human-driven vehicles, suggesting that automated vehicles' decisions about where and when to stop or remain stopped at intersections are more plausible contributing factors than unexpected rates of deceleration.