Research On Signalized Intersection Capacity In Conditions Of Ice And Snow

During the snowing, the snowflakes would affect the driver’s sight, reduce friction coefficient of pavement, make the vehicle traffic environment worse, lesson the driving comfort and make the operation complicate; After the snowing, the road will froze which makes the braking operation complicate and lesson the comfort during the signal intersection traffic light conversion; It’s easy for the driver to be uncomforTable, just like nervous and visual fatigue, etc. While the traffic efficiency and traffic security is lower than the normal pavement. The researches at home and abroad show that the study on the Signal intersection capacity in the snow have an important role on the improving road planning, preventing and fighting natural adversities and improving the efficiency of the network.According to snowfall intensity, basic features of the ice and snow road under the conditions of normal weather, light snow, moderate snow, heavy snow and extremely heavy snow are studied respectively. Based on the survey data, the influence of the ice and snow conditions on the road traffic capacity is analyzed as well with the establishment of the relationship mode between the visibility under snow condition and the snowfall intensity, friction coefficient, as well as the visibility between the snowfall thickness, friction coefficient, and the freezing intensity. Meanwhile, the traffic flow rate mode on the ice and snow conditions is built.The ice and snow conditions can be divided into three types, namely, snowing, freezing and ice-snow mixture. The traffic flow feature mode of the signal intersection under such condition is analyzed on this basis. Through traffic survey and data analysis, the road features under different ice-snow conditions and the traffic flow features of signal intersections are studied, which includes the rate, road friction coefficient and crossing gap under ice-snow conditions. As a result, a comparative study is carried out for the corresponding features under ice-snow conditions and normal weather conditions.Based on the intersection signal control, we respectively studied cycle length and split optimization method. According to the snow and ice conditions of queue length to determine the basis, we introduce matrix needed to determine the optimal signal intersection. Therefore, we established the signal timing of the cycle length and green light time optimization solution in the ice and snow condition. And considering the actual difficulties of driving and vehicle running characteristics under the snow and ice conditions，locus method is used to optimize the yellow light time and vehicle speed characteristics, and complete intersection signal timing optimization scheme under the condition of ice and snow. Take a typical intersection-Huaihe road in Harbin and Songshan road, Hongqi street-Huaihe road data for examples, we use the VISSIM simulation software, make the simulation study on the optimization scheme.For the signal intersection capacity in the snow and ice conditions, we consider the snow and ice conditions as a starting point and base on the signal timing optimization, analyzing the main factors which influence the intersection capacity, including climate, lane function and width. On this basis, respectively, based on HCM method and stop line method, we correct the signal intersection capacity calculation. Based on the HCM method, we overall consider the factors which affect signal intersection capacity in the ice and snow condition and calibrate the overall parameters which affect the signal intersection capacity in the snow and ice conditions. On the basis of stop line method, we calibrate variable parameters, respectively study on variable parameters according to snow weather and frozen conditions and present parameter values in the different conditions. Through the revised model, we calculate the traffic capacity of signal intersection, compare various capacities under the condition of ice and snow, and compared with normal signal intersection traffic capacity in the normal weather.Calibration signal intersection delay model under the condition of ice and snow, which mainly reflected in the visibility and the friction coefficient’s impact on service level, and use it as a signal of an important index of evaluating intersection service level. Through the analysis of survey data and esTablelishing signal intersection traffic arrival rate correction coefficient in the ice and snow condition according to actual situation, its main evaluation factors are visibility and friction coefficient, and finally calibrate under the different weights the correction coefficient of each parameter. On the basis of existing main service level evaluation system, based on the hierarchical analysis，we esTablelish signal road intersection service level’s evaluation index system, at the same time we introduce the selecting process of each index in the evaluation system and evaluation standard. And use the method for Huaihe road, Hongqi street and compare and overall evaluate the intersection signal timing optimization in operation condition, and validate intersection service level after the signal timing optimization under the condition of ice and snow road.