While roundabouts have already been proven to be an effective intersection treatment, there are many instances where low-clearance vehicles have problems using roundabouts. Low-clearance vehicles, such as lowboy trail...While roundabouts have already been proven to be an effective intersection treatment, there are many instances where low-clearance vehicles have problems using roundabouts. Low-clearance vehicles, such as lowboy trailer trucks, have problems, damaging the curbs and truck aprons at roundabouts when there is not sufficient ground clearance. This area has been generally neglected by designers and U.S. states. The latest roundabout manual has guidelines available to design various features of the roundabouts, but they are not specific for low-clearance vehicles. While some previous studies have identified roundabout locations with ground-clearance problems for lowboy trailers that have truck-apron heights that are greater than three inches, no published information is available about truck-apron heights based on three-dimensional analyses. This study addresses the ground-clearance problems for low-clearance vehicles at roundabouts by proposing a procedure where truck-apron heights, truck-apron slope, circulatory roadway slope, and approach roadway slope are analyzed to determine the optimum design measurements for a roundabout’s vertical profile in order to accommodate low-clearance vehicles without terrain conflict. The study procedure was demonstrated on standard single-lane roundabouts and double-lane roundabouts designed according to latest roundabout guide, and recommendations were provided for truck-apron heights and the grade for various features of the roundabouts. This research can guide transportation planners and decision makers when determining the optimum roundabout vertical-profile design when low-clearance vehicles are expected. The study uses TORUS software to design roundabouts, and the AUTOTURN and AUTOTURN Pro 3D software for generating two-dimensional and three-dimensional vehicle simulations as well as for conducting three-dimensional vehicle-clearance analysis.展开更多
文摘[目的]由于FORAN V70 R2.0(及以上版本)输出的JT模型中存在很多同名的特征节点,导致采用间隙分析软件对其进行分析时时间消耗加大且间隙分析结果难以处理。针对该问题,[方法]在研究FORAN导出的JT文件装配结构和蕴含信息(几何信息、材料属性信息等)的基础上,提出一种特征节点合并算法。该算法由坐标变换、模型节点更名、节点几何数据移动和材料属性处理4个步骤构成。然后,利用C++及JT Open Toolkit实现所提出的算法。[结果]结果显示,利用该算法处理后的JT模型只包含1个装配节点且保留了原始JT模型的内在信息,可为后期间隙分析提供有效的输入数据。[结论]大量的实例验证了所提出算法的有效性,处理后的JT文件大小可减少7%~20%。
文摘While roundabouts have already been proven to be an effective intersection treatment, there are many instances where low-clearance vehicles have problems using roundabouts. Low-clearance vehicles, such as lowboy trailer trucks, have problems, damaging the curbs and truck aprons at roundabouts when there is not sufficient ground clearance. This area has been generally neglected by designers and U.S. states. The latest roundabout manual has guidelines available to design various features of the roundabouts, but they are not specific for low-clearance vehicles. While some previous studies have identified roundabout locations with ground-clearance problems for lowboy trailers that have truck-apron heights that are greater than three inches, no published information is available about truck-apron heights based on three-dimensional analyses. This study addresses the ground-clearance problems for low-clearance vehicles at roundabouts by proposing a procedure where truck-apron heights, truck-apron slope, circulatory roadway slope, and approach roadway slope are analyzed to determine the optimum design measurements for a roundabout’s vertical profile in order to accommodate low-clearance vehicles without terrain conflict. The study procedure was demonstrated on standard single-lane roundabouts and double-lane roundabouts designed according to latest roundabout guide, and recommendations were provided for truck-apron heights and the grade for various features of the roundabouts. This research can guide transportation planners and decision makers when determining the optimum roundabout vertical-profile design when low-clearance vehicles are expected. The study uses TORUS software to design roundabouts, and the AUTOTURN and AUTOTURN Pro 3D software for generating two-dimensional and three-dimensional vehicle simulations as well as for conducting three-dimensional vehicle-clearance analysis.