Trends in aggressivity and driver risk for cars, SUVs, and pickups: Vehicle incompatibility from 1989 to 2016

Objective: When 2 vehicles of different sizes collide, the occupants of the smaller vehicle are more likely to be injured than the occupants of the larger vehicle. The larger vehicle is both more protective of its own occupants and more aggressive toward occupants of the other vehicle. However, larger, heavier vehicles tend to be designed in ways that amplify their incompatibility with smaller, lighter vehicles (by having a higher ride height, for example). A 2012 study by the Insurance Institute for Highway Safety (IIHS) concluded that fatalities caused by design incompatibility have decreased in recent years. The current study was conducted to update the 2012 IIHS analysis and to explore trends in vehicle incompatibility over time. Methods: Analyses examined deaths in crashes involving 1- to 4-year-old passenger vehicles from 1989 to 2016 collected from the Fatality Analysis Reporting System (FARS). Trends in driver risk were examined by comparing driver death rates per million registered vehicle years across vehicle type and size. Trends in aggressivity were examined by comparing partner driver death rates across vehicle type and size. Results: Cars and SUVs have continued their trend toward reduced incompatibility. In 1989–1992, SUVs were 132% more likely to kill the driver in a partner car compared with when a car crashed with another car. By 2013–2016, this value had dropped to 28%. Pickups and cars remain just as incompatible in 2013–2016 as they were in 1989–1992, however (159% vs. 158%). Remaining pickup incompatibility may be largely due to excess curb weight rather than to shape or design features, because light pickups were just 23% more likely to kill the driver in a partner car compared with when a car crashed with another car. Conclusions: The trend toward reduced fleet incompatibility has continued in the latest crash data, particularly for cars and SUVs. Although pickup–car incompatibility has also decreased over time, pickups remain disproportionately aggressive toward other vehicles, possibly due to their greater average curb weight. Reducing the weight of some of the heaviest vehicles and making crash avoidance technology fitment more widespread may be promising means to reduce remaining fleet incompatibility. Identifying the source of remaining incompatibility will be important for safety improvements going forward.

研究目标：当不同尺寸的两辆机动车发生碰撞时，小型车辆驾乘人员的受伤概率高于大型车辆驾乘人员。大型车辆既能更好地保护自身驾乘人员，同时对对方车辆驾乘人员的碰撞攻击性更强。然而，更大更重的车辆往往在设计上会放大与小型、轻型车辆的兼容性缺陷——例如采用更高的离地间隙。美国公路安全保险协会（Insurance Institute for Highway Safety, IIHS）2012年的一项研究指出，因设计兼容性缺陷导致的死亡事故近年来有所减少。本研究旨在更新2012年IIHS的分析结果，并探究车辆兼容性缺陷随时间的变化趋势。

研究方法：本分析针对1989年至2016年间、车龄1至4年的乘用车辆碰撞致死案例展开，数据取自死亡分析报告系统（Fatality Analysis Reporting System, FARS）。通过对比不同车辆类型与尺寸的每百万注册车辆年数对应的驾驶员死亡率，分析驾驶员碰撞风险的变化趋势；通过对比碰撞对方驾驶员的死亡率，探究车辆碰撞攻击性的变化趋势。

研究结果：轿车与运动型多用途汽车（SUV）的兼容性缺陷仍呈持续降低趋势。1989-1992年，SUV与轿车碰撞时，造成对方轿车驾驶员死亡的概率较轿车之间碰撞时高出132%；至2013-2016年，该数值已降至28%。不过，皮卡与轿车之间的兼容性缺陷在2013-2016年仍与1989-1992年基本持平（分别为159%与158%）。当前皮卡与轿车的兼容性缺陷主要可能源于其过重的整备质量，而非外形或设计特征：轻型皮卡与轿车碰撞时，造成对方驾驶员死亡的概率仅较轿车之间碰撞时高出23%。

研究结论：最新的碰撞事故数据显示，整体车队的兼容性缺陷改善趋势仍在持续，尤以轿车与SUV领域最为显著。尽管皮卡与轿车的兼容性缺陷也随时间有所降低，但皮卡对其他车辆仍呈现出不成比例的高攻击性，这可能与其更高的平均整备质量有关。降低部分重型车辆的重量，并更广泛地配备碰撞避免技术，或是减少当前车队兼容性缺陷的有效途径。明确当前兼容性缺陷的根源，对未来的交通安全改进至关重要。