《人车特性》PPT课件.ppt
第5讲 人车特性（3）,Chapter 2 Road User and Vehicle Characteristics,2.1 交通系统组成概述2.2 人的特性2.3 车辆特性2.3.1 设计车辆2.3.2 车辆转向性2.3.3 车辆制动性2.3.4 车辆加速性2.4 停车距离及应用,Chapter 2 Road User and Vehicle Characteristics,3,2.3.3 车辆制动性,制动性是汽车行驶时能在短时间内停车且维持行驶方向稳定性和在下长坡时能维持一定车速的能力；可用刹车距离db 来衡量：注：其中S的单位为ft/s假设末速度为0,4,将2-5中S的单位换算为mi/h，并将减速度a用摩擦力系数F代换：,5,考虑纵坡对摩擦力的影响，并设初速度为Si，末速度为Sf：,6,根据美国道路设计标准，湿路面上车辆减速度的标准值为11.2ft/s2，代入(2-6):计算实例见P4142（Once the brakes are engaged）,7,刹车距离公式的用途：交通事故分析；估计实际的摩擦系数；,8,交通事故分析实例(P42):An accident investigator estimates that a vehicle hit a bridge abutment at a speed of 20 mi/h,based on his or her assessment of damage.Leading up to the accident location,he or she observes skid marks of 100 ft on the pavement(F=0.35)and 75 ft on the grass shoulder(F=0.25).There is no grade.An estimation of the speed of the vehicle at the beginning of the skid marks is desired.,9,2.1 交通系统组成概述2.2 人的特性2.3 车辆特性2.3.1 设计车辆2.3.2 车辆转向性2.3.3 车辆制动性2.3.4 车辆加速性2.4 停车距离及应用,Chapter 2 Road User and Vehicle Characteristics,10,2.3.4 车辆加速性,11,主要考虑的是加速距离：注：初速度为零,12,加速距离对比实例(P42):Consider the distance required for a car and a truck to accelerate to 20 mi/h.,13,2.1 交通系统组成概述2.2 人的特性2.3 车辆特性2.4 停车距离及应用2.4.1 安全停车视距2.4.2 反应视距2.4.3 其他视距2.4.4 交通信号的黄灯时间与全红时间,Chapter 2 Road User and Vehicle Characteristics,14,2.4 停车距离及应用,总停车距离反应距离+刹车距离：,15,2.1 交通系统组成概述2.2 人的特性2.3 车辆特性2.4 停车距离及应用2.4.1 安全停车视距2.4.2 决策视距2.4.3 其他视距2.4.4 交通信号的黄灯时间与全红时间,Chapter 2 Road User and Vehicle Characteristics,16,2.4.1 安全停车视距,停车视距：车辆行驶时遇到前方障碍物而必须采取制动停车时所需要最短行车距离；停车视距停车距离时，车辆是安全的；道路安全的重要条件：在道路上的任何一点的视距都大于等于停车视距。,17,计算停车视距的实例（P43）：Consider a section of rural freeway with a design speed of 70 mi/h.On a section of level terrain,what safe stopping distance must be provided?,18,视距不足的实例（P42-43）：What could happen,for example,if a section of this roadway provided a sight distance of only 500 ft?It would now be possible that a driver would initially notice an obstruction when it is only 500 ft away.If the driver were approaching at the design speed of 70 mi/h,a collision would occur.,19,2.1 交通系统组成概述2.2 人的特性2.3 车辆特性2.4 停车距离及应用2.4.1 安全停车视距2.4.2 决策视距2.4.3 其他视距2.4.4 交通信号的黄灯时间与全红时间,Chapter 2 Road User and Vehicle Characteristics,20,2.4.2 决策视距,决策视距：基于不同反应时间得出的，满足不同路况的视距。如果需要停车，用式（2-9）计算视距；如果不需要停车，可用式（2-10）计算视距：,21,计算决策视距的实例（P44）：Consider the decision sight distance required for a freeway section with a 60 mi/h design speed approaching a busy urban interchange with many competing information sources.The approach is on a 3%downgrade.For this case,AASHTO suggests a reaction time up to 14.5 s to allow for complex path and speed changes in response to conditions.,22,2.1 交通系统组成概述2.2 人的特性2.3 车辆特性2.4 停车距离及应用2.4.1 安全停车视距2.4.2 决策视距2.4.3 其他视距2.4.4 交通信号的黄灯时间与全红时间,Chapter 2 Road User and Vehicle Characteristics,23,2.4.3 其他视距,会车视距；错车视距；超车视距；交叉口视距,24,2.1 交通系统组成概述2.2 人的特性2.3 车辆特性2.4 停车距离及应用2.4.1 安全停车视距2.4.2 决策视距2.4.3 其他视距2.4.4 交通信号的黄灯时间与全红时间,Chapter 2 Road User and Vehicle Characteristics,25,2.4.4 交通信号的黄灯时间与全红时间,自学,26,专业词汇,turning characteristicsdesign vehicleturning roadwayintersection curboverhead clearanceshouldersuperelevationcurb setbacksectionapproach,27,专业词汇,gradeupgradedowngradesight distancestopping sight distancehorizontal curvevertical curve decision sight distancepassing sight distance,28,课后作业,习题：2-3，2-4，2-5，2-6笔译：P43左栏第3段（Unfortunately,there is not much that can be done about this disparity in terms of design and control）预习：5.1，5.2,
