Abstract: In order to ensure that the brake failure vehicle can safely slow down and stop after entering braking slope bed in the design of highway escape ramps, the reliability theory was introduced, and the braking slope bed length calculation model of the escape ramps was established under the limit state condition. Then, the reliability function of the braking slope bed length was established based on the proposed model. The related parameters such as the entry speed, rolling resistance coefficient and the braking slope bed gradient were counted and their distribution rule was also analyzed. The Monte Carlo method was used to calculate the reliable probability of the braking slope bed length of the highway escape ramps with the main line design speed of 120, 100 and 80 km/h, respectively. According to the requirement of 95% reliability probability of highway pavement structure, the reliability design of the braking slope bed length of the highway escape ramps was carried out, and the recommended values of the braking slope bed length corresponding to different main line design speeds were given. The results show that: the design value of the brake ramp bed length of the refuge lane changes with the design driving speed, and the reliability probability corresponding to the mainline design speed of 120, 100 and 80 km/h is 39.55%, 46.68% and 54.03% respectively, with insufficient safety and reliability. The recommended safety values for the braking slope bed length corresponding to the main line design speeds of 120, 100, and 80 km/h are calculated based on the corresponding minimum safe design entry speeds of 126, 123, and 122 km/h, as well as the longitudinal slope and slope bed materials selected in the design.

Key words: highway engineering; traffic safety; escape ramps; reliability theory; reliability probability; braking slope bed

摘要： 在进行高速公路避险车道设计时，为保障制动失效车辆进入制动坡床后能安全减速停车，引入可靠度理论，根据极限状态确定避险车道制动坡床长度计算模型，基于该模型构建制动坡床长度的可靠度功能函数，对驶入速度、滚动阻力系数、制动坡床坡度等相关参数进行统计并分析其分布规律，采用蒙特卡罗法计算主线设计速度分别为120、100、80 km/h的高速公路避险车道制动坡床长度的可靠概率。以高速公路路面结构可靠概率95%为要求，对避险车道制动坡床长度进行可靠性设计，给出不同主线设计速度对应的制动坡床长度推荐值。结果表明：避险车道制动坡床长度设计值随着设计驶入速度而变化，120、100、80 km/h主线设计速度对应的可靠概率分别为39.55%、46.68%和54.03%，安全可靠程度不足。主线设计速度为120、100、80 km/h时对应的制动坡床长度安全建议值由对应的最小安全设计驶入速度126、123、122 km/h与设计选取的纵坡和坡床材料综合计算得出。

关键词: 道路工程； 交通安全；避险车道；可靠度理论；可靠概率；制动坡床