Analysis On The Indicator Thresholds Of Roads' Grade Length And Gradient In Xinjiang Main Roads Safety Evaluation

The grade length and gradient of road profile are important indicators of road design. Known from the experiences home and abroad, the grade length and gradient of vertical section and the combination of both are of great effect on road safety. Because of the special topography, the long abrupt down-hills are unavoidable, especially in Xinjiang main roads through mountains, hills and plateaus, so the long abrupt downhill is universal phenomenon. At present, some roads have already become typical traffic accident "Black spot" or "Black belt", and the roads with unreasonable grade length and gradient target of vertical section or the combination of both account for significant proportion. This paper theorizes theoretical mode of brake warming forecast according to mechanical concepts, heat-transfer correlation theories and the law of conservation of energy, and applies observed brake temperature to adjust the mode, then adopts the regression relation mode of traffic accidents happened on main highways in Xinjiang to do further verification, fairly factual brake warming forecast mode will be achieved. In the end, the paper confirms the threshold value of the grade length and gradient of Xinjiang main highways based on the forecast achievement of brake warming forecast model, which provides new train of thought and reference for the road design and safety evaluation of Xinjiang main highways in the near future.