Crash risk of ESC-fitted passenger cars

Objective: We examined both fatal and injury at-fault crashes of a population of passenger cars fitted with electronic stability control (ESC). Crash rates were calculated in relation to both registration years and mileage. Crash rates were also calculated for a non-ESC car population and crash rate ratios were calculated to compare the crash risk between ESC-fitted and non-ESC-fitted passenger cars. Methods: Passenger car models with and without ESC were identified (ESC-equipped cars: 3,352,813 registration years; non-ESC-equipped: 5,839,946 registration years) and their vehicle information for the period 2009–2013, including mileage (ESC-equipped vehicles: 89.3 billion kilometers; non-ESC-equipped: 72.4 billion kilometers), was drawn from the national Vehicular and Driver Data Register. The registry of Finnish road accident investigation teams was accessed and all fatal at-fault crashes among the cars in the study populations (ESC 97; non-ESC 377) for the period 2009–2013 were analyzed. The motor insurance database includes at-fault crashes leading to injuries and was utilized for analyses (ESC: N = 8,827, non-ESC: N = 21,437). Crash rates and crash rate ratios were calculated to evaluate crash risk of both ESC-equipped and non-ESC-equipped passenger cars. Poisson regression was used to model crash involvement rate ratios both per registration year and per mileage for vehicles with ESC and without ESC, controlling for age and gender of the vehicle owner and vehicle mass. Results: Passenger cars fitted with ESC showed lower crash rates than non-ESC-equipped cars in all crash types studied. In general, the difference in crash rates between ESC-equipped and non-ESC-equipped vehicles was greater when the crashes were compared to the mileage rather than registration years. The mileage-proportional crash rate of ESC-equipped cars was 64% (95% confidence interval, 61%; 67%) lower in run-off-road crashes resulting in injury and as much as 82% (65%; 91%) lower in fatal run-off-road crashes when suicides and disease attacks were not taken into account. Conclusions: Our results show that modern passenger cars provide a significant crash risk reduction, which depends on both ESC and passive safety features introduced. Results also show that exposure evaluation in terms of registration years (or vehicle population) instead of true mileage can provide an overly pessimistic view of the crash risk.研究目标：本研究针对配备电子稳定控制系统（Electronic Stability Control, ESC）的乘用车群体，分析其有责致死事故与有责受伤事故。分别以注册年数与行驶里程作为暴露基准计算碰撞率；同时针对未配备ESC的乘用车群体计算碰撞率，并通过碰撞率比对比配备ESC与未配备ESC乘用车的碰撞风险。 研究方法：本研究筛选出配备与未配备ESC的乘用车车型，其中ESC配备车辆共计3,352,813个注册年数，未配备ESC车辆共计5,839,946个注册年数；本研究获取了2009-2013年的相关车辆信息，包括行驶里程（ESC配备车辆：893亿公里；未配备ESC车辆：724亿公里），数据来源于国家车辆与驾驶员数据登记系统（Vehicular and Driver Data Register）。本研究调取了芬兰道路事故调查团队的登记数据库，对2009-2013年期间研究群体车辆中发生的所有有责致死事故进行分析，其中ESC配备车辆涉及97起，未配备ESC车辆涉及377起。同时利用包含有责受伤事故的汽车保险数据库开展分析，其中ESC配备车辆的事故样本量N=8,827，未配备ESC车辆的事故样本量N=21,437。本研究计算碰撞率与碰撞率比，以评估配备与未配备ESC乘用车的碰撞风险；采用泊松回归（Poisson regression）构建模型，分别以注册年数与行驶里程为基准，拟合ESC与非ESC车辆的碰撞涉事率比，并控制车辆所有者的年龄、性别以及车辆质量这三个混杂变量。 研究结果：在所有研究涉及的碰撞类型中，配备ESC的乘用车碰撞率均低于未配备ESC的车辆。总体而言，以行驶里程为基准对比时，ESC配备车辆与未配备车辆的碰撞率差异，比以注册年数为基准对比时更为显著。在不考虑自杀行为与疾病突发导致的事故时，以行驶里程为基准的ESC配备车辆涉伤驶离道路碰撞事故率较未配备车辆低64%（95%置信区间：61%~67%）；在驶离道路导致的致死事故中，该降幅更是高达82%（95%置信区间：65%~91%）。 研究结论：本研究结果显示，现代乘用车可显著降低碰撞风险，该防护效果同时依赖于ESC配置与搭载的被动安全配置。此外，研究结果表明，若以注册年数（或车辆保有量）而非实际行驶里程作为暴露量评估基准，会对碰撞风险得出过于悲观的评估结果。