凝冰路面弯道路段停车视距计算方法

Calculation method for the vehicle stop-range visibility on the curved road with black ice

考虑到我国公路路线设计规范中停车视距计算未涉及弯道参数及路面凝冰引起的路面摩阻系数降低等严重危害车辆行驶安全的因素,以AASHTO模型为基础,通过分析弯道路段车辆行驶时的受力、路面摩阻系数、超高、圆曲线半径等因素推导了凝冰路面弯道路段停车视距计算模型,得出了最不利情况下凝冰路面弯道路段停车视距参考值。当路面发生凝冰现象时,若车辆以交通安全法规规定的冰雪路面最高车速30 km/h行驶,通过对比该行驶速度下凝冰路面弯道路段停车视距与我国规范规定的停车视距可知,没有发挥道路的最大通行能力。以现有道路设计采用的停车视距反算出在役路面发生凝冰现象时的安全行车控制速度,为凝冰路面弯道路段车辆安全行驶控制提供参考。

The present paper takes it as its goal to establish and dedicate a calculating formula to the safe running speed in accordance with the visibility of the stopping distance model. As a matter of fact,the safe running speed for the different kinds of vehicles has been decided by means of the stopping visibility distances for the existing road design. And,in case when the black ice appears on the road surface,the calculation method for the visibility stopping distance in our national highway routine design specification fails to include such important factors as the curve parameters and the road surface friction coefficient deterioration due to the black ice which may bring about serious risks for the vehicle travelling. Rather,the calculation model of the stopping visibility distance should have been deduced based on the AASHTO model by analyzing the force of the vehicle running on the curved road section with the iced pavement,its friction coefficient,its super-elevation and curve radius,all of which can only be determined by referring to the ice-covering visibility stopping distance under the worst case of such sections. Therefore,for the different speeds designated,if the travelling vehicle runs at a maximum speed of 30 km/h as is stipulated by the China state traffic safety regulations on the pavement with black ice when the surface is frozen at a speed of 30 km/h,the road surface cannot be said to display its maximum safety traffic potential capacity,for the friction coefficient between the tire and the paved surface of the curved ice surface section has only 0. 1.And,comparing the stopping visibility distance of the curved road section with the iced pavement under such a speed,the vehicle can not be said to display its maximum potential with the corresponding stopping visibility distance calculated according to the traffic specification as has been China state official regulated.Thus,the analysis results of the function image of the barking distance model in the stopping sight distance under different curve parameters prove that the centripetal force and the superelevation cannot counteract the centrifugal force of the traffic vehicle running at a high speed at the curved road section with the iced pavement under the low friction coefficient,rather it is the traffic vehicle that tends to be sideslipped. Based on the above performed sufficient analysis in accordance with the calculation formula for the safe running speed of the stopping sight distance model,the present paper has worked out the safety controlling speed of the traffic vehicles by means of the visibility stopping distance for the existing road design when the black ice appears on the pavement surface.