中文摘要：

针对公路最小直线长度多次规范修订时的不明确以及在实际应用中存在的问题,收集国内外相关资料进行对比,发现各国的规定值有差异,也确定了我国指标值的出处;其次,考虑车辆运行时,超高过渡、加减速及驾驶员操作的需要,采用力学、运动学的方法,从理论上推导出满足以上要求的最小直线长度模型;再次,考虑驾驶员舒适性要求,建立各种线形组合下的三维模型,借助透视图分析方法,建立满足舒适性要求的最小直线长度模型;最后,综合以上几方面给出了最终的最小直线长度模型。研究结果表明：对于同向曲线之间的最小直线长度,满足视觉舒适性要求是最主要的,且其值随着半径的增大而减小;对于反向曲线之间的最小直线长度,超高过渡和离心加减速度变化率是控制因素,但两个最小长度值均比现有规范值小。该结论得到某国道改造项目的验证,并有助今后规范的修订。

英文摘要：

The highway minimum tangent lengths in the recent versions of Design Specification for Highway Alignment present uncertainty that leads mixed guidance in application.To solve this problem,first,different data of the minimum tangent lengths in some representative countries were collected and compared,and found out the source from where the minimum tangent lengths of China came.Second,using mechanics and kinematics theories,three minimum tangent length models were established,considering the superelevation runoff,acceleration-deceleration transition rate and driving operation demand during the travel.Then,in terms of driving comfort,the minimum tangent length model was established by perspective method on the basis of 3D model of different combinations of horizontal and vertical alignment.Based on the above all,the comprehensive minimum tangent length model was established.It is concluded that（1） for the minimum tangent length on curves in the same direction,visual comfort requirement is the key factor,and the value decrease as the radii increase;（2） for the minimum tangent length on curves in opposite directions,superelevation runoff and centrifugal acceleration-deceleration transition rate are dominant factors.Both the two minimum lengths are less than that in the specification.The conclusions were tested and verified available by a national arterial highway reconstruction project and is useful for the future revision of the Specification.