中文摘要：

驾驶员在追尾临撞工况下的避撞过程可以分为多个阶段（如制动前、制动后），而在每一阶段中，又存在多个分析角度（如制动快慢、制动力度）及不同的关键时刻与特征值，因此系统描述驾驶员的避撞行为需要多种参数．对多种避撞行为参数进行降维处理，并探究工况紧急程度对每类参数的综合影响．利用同济大学8自由度高仿真驾驶模拟器，研究驾驶员在不同前车减速度（0．30g，0．50g，0．75g）和不同初始车头时距（1．5s，2．5s）下的避撞行为，全面记录了驾驶员危险感知、油门释放和刹车制动等避撞行为参数．利用主成分分析对众多参数进行降维处理，将避撞行为特征划分为感知反应、制动延误、制动力度3个方面，并通过多元方差分析探究车头时距、前车减速度及二者交互项对这3个方面的影响．结果表明，驾驶员感知反应受到车头时距和前车减速度同时影响，制动延误受到车头时距、前车减速度以及二者交互项的影响，制动力度则仅受到前车减速度的影响．在变化趋势上，随着工况紧急程度的增加，驾驶员的感知反应越快，制动延误越短，而制动力度越大．

英文摘要：

The process of collision avoidance under rear-end scenarios can be divided into several stages （e. g., pre-brake and post-brake ）. In each stage, different analysis perspectives （e. g., brake delay and brake intensity） exist, and different key time moments and measurements can be defined. Therefore, lots of parameters are involved in systematically describing drivers ＇ collision avoidance behaviors. Studies that focused on a certain parameter can only give information on a specified parameter rather than the underlying behavioral patterns behind the parameters. This study did dimension reduction analyses for the multiple parameters of collision avoidance behaviors, and investigated the impacts of situational urgency on each type of parameters. The high fidelity Tongji University driving simulator was used to test drivers＇ collision avoidance behaviors under different initial headways （1. 5 s, 2. 5 s） and different lead vehicle （LV） deceleration rates （0.30g, 0.50g, 0.75g）. Parameters characterizing drivers＇ hazard perception, throttle releasing and braking process were recorded. Dimension reduction analyses on collision avoidance behaviors was conducted with principal component analysis, which generalized collision avoidance behaviors into three aspects., perception response, braking delay and braking intensity. Multivariate analysis of variance was applied to investigate how initial headway and LV deceleration affect these three aspects. Results showed that perception response was affected by both initial headways and LV deceleration; braking delay was affected by initial headway, LV deceleration and their interaction simultaneously; and braking intensity depended solely on lead vehicle＇s deceleration. As situational urgency increased, drivers responded faster and braked to maximum more quickly, and braked harder.