研究目的：山区高速公路为适应地形,常被迫采用连续长大纵坡。国内外针对长大纵坡设置在规范中提 出诸多限制，然而因载重车辆下坡制动失效引发的交通事故仍层出不穷。据调查,法国长大纵坡路段交通事故发生率明显低于我国，这大部分得益于其规范的合理性和有效性。本文通过案例的归纳，分析载重车辆下坡制动性能损失的原因，并参考法国现行标准以及相关规定，提出长大纵坡风险指标及降低行车风险而采取的措施,为国内高速公路设计提供参考。
研究结论:对高速公路下坡度大于3%路段,纵断面设计中避免在大坡道间频繁插入缓和坡道。当高差达到130m时,建议设置避险车道。同时需要增设预告标志,并在有条件的段落建议设置慢行车道，以便有效降低行车风险和保护司乘人员安全。
Research purposes: To adapt the terrain condition of mountainous area, the large longitudinal slope often has to be built to the highway in mountain area. For building the large longitudinal slope, there are many restrictions stipulated in the specifications at home and abroad. However, the traffic accidents caused by the braking failure of the heavily loaded vehicle in down slope still happen from time to time. The investigation shows the incidence of the traffic accident happened in the large longitudinal slope in France is much lower than China because the French specifications are more rational and effective. Based on inducting and analyzing the cases, this paper analyzes the reason for the braking failure of the heavily loaded vehicle in down slope, presents the risk indicators of the large longitudinal slope based on referencing the current French specifications and relevant provisions and gives the measures for reducing the driving risks for the purpose of providing the reference to highway design.
Research conclusions: In the highway's section with the large longitudinal slope of more than 3%, the gentle slopes should not be designed frequently. The emergency lane should be built when the elevation difference of one large longitudinal slope reaches at 130 meters. In addition, the warning signs should be added and the slow lane should be built in the conditional section to reduce the driving risk and protect the driver and the other people.
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