| Longitudinal slope is one of the key index for road alignment design in more snow and ice city, which affects the cost of road construction, traffic safety and capacity. This paper research longitudinal slope indicators for city roads ground and elevated ramp under snow and ice conditions, from the view of road level of service, traffic safety, vehicle dynamic performance, relied on Natural Science Foundation of Heilongjiang Province; It proposes a suggested values for the design indicators which can become a reference for city road alignment design and road network reliability in more snow and ice area.Through qualitative analysis of various physical properties of snow and ice roads, we classify the types according to the state of ice and snow road surface. Firstly, we measure the speed of longitudinal sections under snow and ice conditions, friction coefficient of various types of road surface of ice and road longitudinal grade index. Then, analysis was taken to the distribution characteristics of the speed on longitudinal sections under snow and ice conditions, relationship between friction coefficient and types of ice and snow road surface , tire structure,tread pattern and speed and relationship between Gradient and speed. Finally, the relationship model of slope and speed was built.According to the design basis of the maximum longitudinal slope, the maximum slope length, we propose three kinds of method for longitudinal design indicators of road surface under ice and snow conditions: when vehicle going uphill, slope length indicators design considering service level of Longitudinal sections and the size of the different speed between different size of vehicles.; when vehicle going downhill, the slope length design should take to the driver's heart rate. Finally, combine these three methods to determine the slope length limit of longitudinal ground road under snow and ice conditions. According to traffic theory and consider the fact that the vehicle traction was restricted by the road friction conditions of snow and ice surface, we establish the maximum climbing ability model of vehicle under snow and ice conditions to calculate the mass / power ratio which expressing the maximum climbing ability for different type of vehicle and different road surface under snow and ice. Besides, we calculate the park slope parking of different type of vehicle under different snow and ice conditions and give an recommended value for maximum longitudinal slope of road length and slope in more snow and ice city.Based on the traffic characteristics of the elevated road up-ramp, with the adhesion limit between wheel and ice road when the vehicle start acceleration on the ramp and the fact that the maximum longitudinal slope of on ramp shall not exceed the maximum climbing gradient when the vehicle travel with I taps under snow and ice condition, we get the maximum longitudinal Limit on ramp under snow and ice condition. According to the traffic characteristics of the elevated road down-ramp and consider the changes of friction coefficient on snow and ice road surface, we research the longitudinal index of ramp from the road safety point and propose that the length of slope for elevated road down-ramp should be greater than 2 times of the stopping sight of the recommendation, so the maximum longitudinal limit of elevated road down-ramp in the snow and ice conditions was got.In addition, with the complex interwoven features existed on connection of elevated and surface roads, this chapter particularly focus on the minimum distance limit between longitudinal foot of a elevated road ramp and the intersection on ground. Calculation model of minimum distance between raised foot of the elevated road up-ramp and the intersection corner cutoff on ground was proposed, as well as the optimization method for minimum distance between longitudinal foot of a elevated road ramp and the intersection on ground based on VISSIM.
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