Kusano Kristofer D, Gabler Hampton C
a Virginia Tech , Blacksburg , Virginia.
Traffic Inj Prev. 2015;16 Suppl 2:S109-14. doi: 10.1080/15389588.2015.1063619.
The U.S. New Car Assessment Program (NCAP) now tests for forward collision warning (FCW) and lane departure warning (LDW). The design of these warnings differs greatly between vehicles and can result in different real-world field performance in preventing or mitigating the effects of collisions. The objective of this study was to compare the expected number of crashes and injured drivers that could be prevented if all vehicles in the fleet were equipped with the FCW and LDW systems tested under the U.S. NCAP.
To predict the potential crashes and serious injury that could be prevented, our approach was to computationally model the U.S. crash population. The models simulated all rear-end and single-vehicle road departure collisions that occurred in a nationally representative crash database (NASS-CDS). A sample of 478 single-vehicle crashes from NASS-CDS 2012 was the basis for 24,822 simulations for LDW. A sample of 1,042 rear-end collisions from NASS-CDS years 1997-2013 was the basis for 7,616 simulations for FCW. For each crash, 2 simulations were performed: (1) without the system present and (2) with the system present. Models of each production safety system were based on 54 model year 2010-2014 vehicles that were evaluated under the NCAP confirmation procedure for LDW and/or FCW. NCAP performed 40 LDW and 45 FCW tests of these vehicles.
The design of the FCW systems had a dramatic impact on their potential to prevent crashes and injuries. Between 0 and 67% of crashes and 2 and 69% of moderately to fatally injured drivers in rear-end impacts could have been prevented if all vehicles were equipped with the FCW systems. Earlier warning times resulted in increased benefits. The largest effect on benefits, however, was the lower operating speed threshold of the systems. Systems that only operated at speeds above 20 mph were less than half as effective as those that operated above 5 mph with similar warning times. The production LDW systems could have prevented between 11 and 23% of drift-out-of-lane crashes and 13 and 22% of seriously to fatally injured drivers. A majority of the tested LDW systems delivered warnings near the point when the vehicle first touched the lane line, leading to similar benefits. Minimum operating speed also greatly affected LDW effectiveness.
The results of this study show that the expected field performance of FCW and LDW systems are highly dependent on the design and system limitations. Systems that delivered warnings earlier and operated at lower speeds may prevent far more crashes and injuries than systems that warn late and operate only at high speeds. These results suggest that future FCW and LDW evaluation should prioritize early warnings and full-speed range operation. A limitation of this study is that additional crash avoidance features that may also mitigate collisions-for example, brake assist, automated braking, or lane-keeping assistance-were not evaluated during the NCAP tests or in our benefits models. The potential additional mitigating effects of these systems were not quantified in this study.
美国新车评估计划（NCAP）目前对前方碰撞预警（FCW）和车道偏离预警（LDW）进行测试。这些预警在不同车辆之间的设计差异很大，可能导致在预防或减轻碰撞影响方面出现不同的实际现场表现。本研究的目的是比较如果车队中的所有车辆都配备在美国NCAP下测试的FCW和LDW系统，预计可预防的撞车事故数量以及受伤驾驶员数量。
为了预测可能预防的潜在撞车事故和严重伤害，我们的方法是对美国撞车事故总体进行计算建模。这些模型模拟了在一个具有全国代表性的撞车事故数据库（NASS - CDS）中发生的所有追尾和单车道路偏离碰撞事故。来自2012年NASS - CDS的478起单车撞车事故样本是进行24,822次LDW模拟的基础。来自1997 - 2013年NASS - CDS的1,042起追尾碰撞事故样本是进行7,616次FCW模拟的基础。对于每起撞车事故，进行了2次模拟：（1）系统不存在时；（2）系统存在时。每个生产安全系统的模型基于54辆2010 - 2014车型年的车辆，这些车辆是根据NCAP对LDW和/或FCW的确认程序进行评估的。NCAP对这些车辆进行了40次LDW测试和45次FCW测试。
FCW系统的设计对其预防撞车事故和伤害的潜力有巨大影响。如果所有车辆都配备FCW系统，在追尾碰撞中，0%至67%的撞车事故以及2%至69%的中度至致命受伤驾驶员本可避免。更早的预警时间带来了更大的益处。然而，对益处影响最大的是系统的较低运行速度阈值。仅在速度高于20英里/小时时运行的系统，其有效性不及那些在类似预警时间下速度高于5英里/小时时运行的系统的一半。量产的LDW系统本可预防11%至23%的车道偏离撞车事故以及13%至22%的严重至致命受伤驾驶员。大多数测试的LDW系统在车辆首次接触车道线时附近发出预警，带来了类似的益处。最低运行速度也极大地影响了LDW的有效性。
本研究结果表明，FCW和LDW系统的预期现场表现高度依赖于设计和系统限制。更早发出预警且在较低速度下运行的系统，相比那些预警晚且仅在高速下运行的系统，可能预防更多的撞车事故和伤害。这些结果表明，未来FCW和LDW评估应优先考虑早期预警和全速度范围运行。本研究的一个局限性是，在NCAP测试或我们的益处模型中未评估其他可能也减轻碰撞的防撞功能，例如制动辅助、自动制动或车道保持辅助。本研究未对这些系统的潜在额外减轻影响进行量化。
