Horizontal alignment greatly affects the speedof vehicles at rural roads. Therefore, it is necessary toanalyze and predict vehicles speed on curve sections.Numerous studies took rural two-lane as research subjectsand ...Horizontal alignment greatly affects the speedof vehicles at rural roads. Therefore, it is necessary toanalyze and predict vehicles speed on curve sections.Numerous studies took rural two-lane as research subjectsand provided models for predicting operating speeds.However, less attention has been paid to multi-lane highwaysespecially in Egypt. In this research, field operatingspeed data of both cars and trucks on 78 curve sections offour multi-lane highways is collected. With the data, correlationbetween operating speed （V85） and alignment isanalyzed. The paper includes two separate relevant analyses.The first analysis uses the regression models toinvestigate the relationships between V85 as dependentvariable, and horizontal alignment and roadway factors asindependent variables. This analysis proposes two predictingmodels for cars and trucks. The second analysisuses the artificial neural networks （ANNs） to explore theprevious relationships. It is found that the ANN modelinggives the best prediction model. The most influential variableon V85 for cars is the radius of curve. Also, for V85 fortrucks, the most influential variable is the median width.Finally, the derived models have statistics within theacceptable regions and they are conceptually reasonable.展开更多
弯道交通事故高发,车辆超速行驶、潮湿路面抗滑性能不足及离心力作用所造成的车辆侧向滑移是其主要事故类型。明确潮湿弯道车辆最大安全行驶速度对于保证弯道安全驾驶至关重要,由于轮胎-水流-路面之间的相互作用机理复杂,涉及变量较多(...弯道交通事故高发,车辆超速行驶、潮湿路面抗滑性能不足及离心力作用所造成的车辆侧向滑移是其主要事故类型。明确潮湿弯道车辆最大安全行驶速度对于保证弯道安全驾驶至关重要,由于轮胎-水流-路面之间的相互作用机理复杂,涉及变量较多(包括弯道几何参数、路面表面特征、轮胎运动特性、水膜厚度等),目前还没有从抗滑模拟角度获取降雨工况下弯道最大安全行驶速度的工程实践。基于固体力学和流体力学,建立轮胎-水流-路面耦合的侧偏抗滑模型,并依据抗滑测试值对模型预测准确性进行验证。以侧偏抗滑模型为基础,结合侧滑机理分析,得到所验证沥青路面在不同弯道半径、超高和水膜厚度下的最大安全行驶速度,并与美国国家公路与运输协会(American Association of State Highway and Transportation, AASHTO)设计速度进行对比。结果表明:现有设计速度规范对雨天环境因素考虑不足,当降雨强度较大时,车辆以AASHTO设计速度行驶会发生侧向滑移。该结果验证了所建立侧偏抗滑模型求解最大安全车速的方法对识别具有高滑移风险的雨天环境状况和低抗滑性能路面的有效性,并可为弯道路面摩擦管理和混合料设计提供新手段。展开更多
文摘为了研究平、竖曲线路段绿化植物的防眩效果,提出了平直路段防眩植物株距和高度的计算方法,并计算了不同植物冠径和防眩角条件下的株距,以及不同道路横断面和交通组成条件下的防眩植物高度.对平曲线路段,提出了改进的防眩植物株距计算方法,计算了防眩角修正值;对竖曲线路段,提出了改进的防眩植物高度计算方法,计算了凹曲线路段防眩植物高度增高值,提出了凸曲线植物下沿防眩改善措施.研究结果表明：相对平直路段,平曲线路段防眩植物株距应减小0.3～3.8 m;凹曲线路段防眩植物高度应增加0.03～0.43 m.
文摘为了研究车辆在单曲线上行驶时的运动学行为和驾驶行为,在ADAMS软件环境下创建了小客车的动力学模型,进行了切弯和跟弯两种驾驶模式的单曲线行驶试验.根据仿真输出的转向盘角度变化,将转向过程划分为进弯、维持和出弯3个阶段,分别得到了车辆进弯和出弯时的转向长度和转向时间,以及这2个参量与弯道半径、转角和车辆轴距的关系.研究结果表明:当弯道转角不超过某个临界值时,转向盘转角、转向时间以及转向长度随着弯道转角的增大而增大,并且切弯时更显著;当弯道半径不超过550 m时,转向长度随弯道半径增大而增大;不同驾驶模式会导致转向长度出现显著差别,切弯时的稳定转向长度约为跟弯时的2倍;切弯模式的"稳定转向时间-弯道半径"曲线先升后降,呈抛物线形状,而采用跟弯模式时该曲线呈单调下降趋势,2种模式的平均转向时间为3.75 s.
文摘Horizontal alignment greatly affects the speedof vehicles at rural roads. Therefore, it is necessary toanalyze and predict vehicles speed on curve sections.Numerous studies took rural two-lane as research subjectsand provided models for predicting operating speeds.However, less attention has been paid to multi-lane highwaysespecially in Egypt. In this research, field operatingspeed data of both cars and trucks on 78 curve sections offour multi-lane highways is collected. With the data, correlationbetween operating speed （V85） and alignment isanalyzed. The paper includes two separate relevant analyses.The first analysis uses the regression models toinvestigate the relationships between V85 as dependentvariable, and horizontal alignment and roadway factors asindependent variables. This analysis proposes two predictingmodels for cars and trucks. The second analysisuses the artificial neural networks （ANNs） to explore theprevious relationships. It is found that the ANN modelinggives the best prediction model. The most influential variableon V85 for cars is the radius of curve. Also, for V85 fortrucks, the most influential variable is the median width.Finally, the derived models have statistics within theacceptable regions and they are conceptually reasonable.
文摘弯道交通事故高发,车辆超速行驶、潮湿路面抗滑性能不足及离心力作用所造成的车辆侧向滑移是其主要事故类型。明确潮湿弯道车辆最大安全行驶速度对于保证弯道安全驾驶至关重要,由于轮胎-水流-路面之间的相互作用机理复杂,涉及变量较多(包括弯道几何参数、路面表面特征、轮胎运动特性、水膜厚度等),目前还没有从抗滑模拟角度获取降雨工况下弯道最大安全行驶速度的工程实践。基于固体力学和流体力学,建立轮胎-水流-路面耦合的侧偏抗滑模型,并依据抗滑测试值对模型预测准确性进行验证。以侧偏抗滑模型为基础,结合侧滑机理分析,得到所验证沥青路面在不同弯道半径、超高和水膜厚度下的最大安全行驶速度,并与美国国家公路与运输协会(American Association of State Highway and Transportation, AASHTO)设计速度进行对比。结果表明:现有设计速度规范对雨天环境因素考虑不足,当降雨强度较大时,车辆以AASHTO设计速度行驶会发生侧向滑移。该结果验证了所建立侧偏抗滑模型求解最大安全车速的方法对识别具有高滑移风险的雨天环境状况和低抗滑性能路面的有效性,并可为弯道路面摩擦管理和混合料设计提供新手段。
