道路超高过渡方式分析、探讨

我国《公路路线设计规范》对超高缓和段的设计方式没有明确规定,工程实践中超高过渡大多是在缓和曲线上进行。从理论上讲,这种方式存在进入弯道开始路段外侧车道无法抵抗离心力的不足。美国AASHTO《绿皮书》《公路与城市道路几何设计政策》中对超高设计方式有详细的规定,各类超高过渡的共同特点是在进入弯道（缓和曲线或圆曲线）前先有1个直线过渡段,使外侧车道进入弯道即可抵抗离心力。经过实例计算、比较分析,认为AASHTO《绿皮书》超高过渡方式更加缓和,更有利于行车安全,文中还分析了AASHTO《绿皮书》超高过渡方法用于我国工程实践的条件和可能性。

Superelevation Transition Methods of Roadway

Presently the method of roadway superelevation transition（run-off） is not stipulated clearly in the Highway Route Design Specification in China.Most of the transition in practice is accomplished within the full-length of transition curve.However,this method bears the defect that the centrifugal force affects the vehicles at outside lanes when vehicles enter the beginning section of the curve.In the United States,there are detailed regulations in AASHTO Green Book（A Policy on Geometric Design of Highways and Streets,2004） where a straight-line transition segment is set before entering curve（transition curve or circular curve）.Thus,no centrifugal force occurs when vehicles enters curve and safer driving is obtained.This paper concludes that the transition method in AASHTO is completed more gently than that in Highway Route Design Specification.Through the calculation and analysis of an example,this paper also discusses the conditions and possible application of the AASHTO superelevation transition methods in China.