The effect of vehicle countermeasures and age on human volunteer kinematics during evasive swerving events

Objective: Emergency maneuvers such as evasive swerving often precede a crash. These events are typically low-acceleration, time-extended events where the inertial forces have the potential to cause changes to the occupant’s initial state (initial posture, position, muscle tension). The objective of this study was to systematically quantify the kinematics of pediatric and adult human volunteers during simulated pre-crash evasive swerving maneuvers and evaluate the effect of age and two vehicle-based countermeasures. Methods: A novel laboratory device was designed to expose subjects to non-injurious loading conditions that mimic real-world evasive swerving events. A four-cycle oscillatory lateral pulse with a maximum acceleration of 0.72 g (0.53 g for the first lateral movement in the first cycle) was applied. Forty seat belt restrained subjects across four age groups – 9-11 years (n = 10), 12-14 years (n = 10), 15-17 years (n = 10) and 18-40 years (n = 10) – were exposed to a series of test conditions (baseline, pre-pretensioned seat belt, sculpted vehicle seat with and without inflated torso bolsters) while their kinematics were captured using 3 D motion capture and muscle activity was recorded. Reaction loads were collected from the shoulder belt and footrest. Data are presented for the first cycle only. Results: Pre-pretensioning the shoulder belt before the onset of acceleration had the greatest restraining effect on the head and trunk for all age groups. In the pre-pretensioning trials, compared to baseline, subjects exhibited 34% and 33% less head excursion, into and out of the shoulder belt respectively. Similar reductions were observed with pre-pretensioning for trunk excursion (45% and 53% reductions, in and out of the belt respectively). Inflating seat torso bolsters reduced lateral kinematics relative to baseline but to a lesser extent than the pre-pretensioner (Head Out of belt: 11%; Head Into Belt: 32% and Trunk Out of Belt: 15%; Trunk Into Belt: 27%). Although there was no overall effect of age on the magnitude of lateral displacement, different age groups employed various neuromuscular strategies to control their kinematics. Conclusion: A pre-pretensioner was an effective vehicle countermeasure during evasive swerving maneuvers as it substantially reduced lateral head and trunk displacement for all age groups. Providing lateral restraint via a sculpted vehicle seat was less effective as the geometry of the torso bolsters when inflated did not provide substantial lateral support.

研究目的：紧急避让转向等应急驾驶操作通常发生在碰撞前。此类事件多为低加速度、时程较长的过程，惯性力可能改变乘员的初始状态（初始姿势、位置及肌肉张力）。本研究旨在系统量化模拟撞前避闪转向动作过程中，儿童与成年人体受试者的运动学（kinematics）特征，并评估年龄因素与两种车载防护措施的影响。

试验方法：本研究设计了一款新型实验室装置，可在无损伤加载条件下模拟真实场景中的避闪转向事件。该装置施加了四周期振荡侧向脉冲，最大加速度为0.72g（第一周期的首次侧向运动加速度为0.53g）。共招募40名经安全带约束的受试者，分为四个年龄组：9~11岁组（n=10）、12~14岁组（n=10）、15~17岁组（n=10）及18~40岁组（n=10）。受试者依次参与多组测试工况：基准工况、预紧式安全带（pre-pretensioned seat belt）工况、带/不带充气式躯干支撑垫的造型座椅工况。试验过程中，采用三维运动捕捉系统采集受试者运动学数据，并同步记录肌肉活动信号；同时采集肩带与脚踏板的反作用力数据。本研究仅呈现第一周期的试验数据。

试验结果：在所有年龄组中，加速度触发前预紧肩带对头部与躯干的约束效果最优。与基准工况相比，预紧安全带工况下受试者朝向肩带与背离肩带的头部偏移量分别降低34%与33%；躯干偏移量同样出现类似降幅：朝向肩带与背离肩带时分别降低45%与53%。充气式躯干支撑垫相比基准工况可降低侧向运动学响应，但效果弱于预紧式安全带：朝向肩带的头部偏移量降低32%、背离肩带降低11%；躯干偏移量则分别降低27%（朝向肩带）与15%（背离肩带）。尽管年龄因素对侧向位移的整体幅度无显著影响，但不同年龄组采用了各异的神经肌肉策略来调控自身运动学响应。

结论：预紧式安全带在避闪转向动作中是一种高效的车载防护措施，可显著降低所有年龄组受试者的头部与躯干侧向位移。通过造型座椅提供侧向约束的效果相对有限，原因在于充气后的躯干支撑垫几何结构无法提供充足的侧向支撑。