《交通工程专业英语翻译》.docx

Design of the Alignment线形设计 The alignment of a highway is composed of vertical and horizontal elements. The vertical alignment includes straight (tangent) highway grades and the parabolic curves that connect these grades. The horizontal alignment includes the straight (tangent) sections of the roadway and the circular curves that connect their change in direction. 公路线形包括平曲线和竖曲线元素。竖曲线包括直坡线（切线）和连接这些直坡线的抛物线。平曲线包括公路的直线部分（切线）和连接两直线并转向的圆曲线。 The design of the alignment depends primarily on the design speed selected for the highway. The least costly alignment is one that generally takes the form of the natural topography. It is not always possible to select the lowest cost alternative because the designer has to adhere to certain standards that may not exist on the natural topography. 线形的设计取决于公路的设计速度。最经济的线形是沿着自然地形展线。现实中设计师往往不能选择造价最低的方案，因为他们必须遵循特定的技术标准，而这些标准在自然地形中也许难以达到。 It is important that the alignment of a given section has consistent standards to avoid sudden changes in the vertical and horizontal layout of the highway. It is also important that both horizontal and vertical alignments be designed to complement each other, since this will result in a safer and more attractive highway. 重要的是给定部分的线形必须符合规范来避免公路在水平和竖直布局上产生突变。同样重要的是设计的平曲线和竖曲线要相互协调，因为这样才能设计出安全并更有吸引力的公路。 One factor that should be considered to achieve compatibility is the proper balancing of the grades of tangents with curvatures of horizontal curves and the location of horizontal and vertical curves with respect to each other. For example, a design that achieves horizontal curves with large radii at the expense of steep or long grades is a poor design. Similarly, if sharp horizontal curves are placed at or near the top of pronounced crest vertical curves or at or near the bottom of a pronounced sag vertical curve, a hazardous condition will be created at these sections of the highway. Thus, it is important that coordination of the vertical and horizontal alignments be considered at the early stages of