Effects of vehicle load characteristics on distributions of time-to-collision

Abstract

Time-to-collision (TTC), which is affected by vehicle load characteristics, is considered as an effective index for the risk assessment of the car- following process in collision avoidance systems. This research uses vehicle type, overweight and speeding to quantify vehicle load characteristics. Twelve types of car- following scenarios under free- flow conditions were decomposed with different load characteristics of the leading and following vehicles. The weigh-in-Motion (WIM) technique is applied to obtain traffic flow data that combines the load characteristics. The influence of vehicle load characteristics on TTC distribution in the 12 types of car-following scenarios was analyzed. The significance of TTC distribution was compared using KS test. Results show that the distribution of TTC cumulative frequency fits an exponential distribution. At the 5% level of significance, vehicle class and speeding do not show a significant effect on TTC distribution. Overweight of light vehicles has significant effect on TTC distribution. And overweight increases the potential conflict risk in the scenarios of a light vehicle following a heavy/light vehicle. In the case that the leading and following vehicles are not speeding, the potential conflict risk in the scenario of a light vehicle following a heavy vehicle is higher than the scenario of a light vehicle following a light vehicle. 受车辆荷载特性影响的碰撞时间(Time-To-Collision, TTC)，被认为是车辆避撞系统中跟驰过程风险评估的有效指标 . 本文以车辆类型、超重和超速指标量化表征车辆荷载特性，分解前后车辆不同荷载特性组合的 12 类跟驰场景 . 基于动态称重技术获取融合荷载特性的交通流数据，分析车辆荷载特性对自由流交通状态下 12 类跟驰场景 TTC 分布的影响，利用 KS检验对比 TTC 分布的显著性 . 结果表明：TTC 累计频率分布服从指数模型，在 5%置信度水平上，跟驰前后车的车辆类型对 TTC 分布无显著影响；前后车均为超重轻车显著增加了潜在冲突风险，超重增加了轻车跟驰重车，轻车跟驰轻车场景的潜在冲突风险；前后车不超速跟驰场景下，轻车跟驰重车的风险比例高于轻车跟驰轻车.