基于制动减速度的高速公路停车视距研究

Study on Parking Sight Distance of Expressway Based on Braking Deceleration

为了研究《路线规范》中确定停车视距指标时采用设计速度的85%或90%与实际情况不符的问题,采用高速公路的实测各车道速度数据,分析了各车道的车辆运行速度分布特征。从运动学原理出发对汽车制动过程进行分析,将车辆制动过程分为驾驶人反应时间、制动系统协调时间及全制动时间3个时间段,建立了基于制动减速度的车辆制动模型,并对模型中驾驶人反应时间、制动减速度和运行速度等关键参数进行深入试验调查和分析研究。分别提出了平坡段小客车与货车在相对舒适和紧急制动两种情况下的停车视距建议值,并提出了不同纵坡条件下的货车停车视距修正值。结果表明:在平坡路段相对舒适情况下的停车视距与AASHTO中的规定值基本一致;紧急制动情况下的停车视距与我国规范值基本一致,比目前《路线规范》条文中采用折减后的设计速度计算停车视距的解释更加合理。纵坡对货车停车视距影响较大,因此纵坡段以货车停车视距为研究对象,并从安全角度考虑选择采用相对舒适的制动减速度得到的停车视距作为建议值,为《路线规范》规定的停车视距值的应用和解释提供了更好的依据。

In order to study the problem that 85% or 90% of the design speed used when determining the parking sight distance indicator in the Design Specifications for Highway Alignment does not match the actual situation, the measured speed data of each lane of expressway is used to analyze the distribution characteristics of vehicle running speeds in each lane. The braking process of the vehicle is analyzed by the kinematics principle, and the entire braking process of the vehicle is divided into driver reaction time, braking system coordination time and full braking time. A vehicle braking model based on braking deceleration is established. The key parameters in the model such as the driver’s reaction time, braking deceleration and vehicle operating speed are deeply investigated and studied. The values of stopping sight distance for cars and trucks under relative comfort and emergency braking in flat slope sections are suggested respectively, and the corrected values of stopping sight distance for trucks under different longitudinal slope conditions are also proposed. The result shows that(1) The stopping sight distance under relatively comfortable conditions on flat slope is basically the same as the specified value in AASHTO.(2) The stopping sight distance under emergency braking is basically the same as Chinese standard value, which is more reasonable than the interpretation of the stopping sight distance calculated by the reduced design speed in current Design Specifications for Highway Alignment.(3) The longitudinal slope has a great influence on the stopping sight distance of truck. Therefore, the stopping sight distance of truck is the research object for longitudinal slope section, and the stopping sight distance obtained by adopting relatively comfortable braking deceleration is selected as the recommended value from the perspective of safety. It provides a better basis for the application and interpretation of the stopping sight distance values specified in the Design Specifications for Highway Alignment.