Research On Safety Design Of Main And Side Road Exits In Urban Expressway

Urban expressway transect layout generally set the main and side roads, monolithic ground is its base form. At present the settings of main and side road exit generally consult the design standard of interchange ramp exit.The field investigation shows that the traveling track is S-shape. Vehicle control is difficult, causing rear-end collision and hitting lateral zonation of traffic accidents easily. Urban expressway design code in China is mainly based on the main design speed, lacking of the design speed of side road, traffic volume of main and side roads, drivers’ characteristics and other factors.This paper studys on the security setting of the exit of the ground main and side road, exporting to reduce traffic accidents and improving the safety level of urban expressway operation.First of all, chosing four exits of main and side road in Nanjing jiangbei avenue and jiangdong expressway as field investigations.Through data analysis, it concluds that the running speed distribution rule of main and side road,and the distribution features of the vehicle out of speed and out of position.Secondly, according to the driving characteristics of main and side roads exit area, the paper conducts the analysis of the vehicle deceleration and driver’s psychological characteristic affecting driving safety.Again, applying UC-win/Road test driving simulation platform to retardation test, it extracts from speed and maximum speed reduction. Stduying traffic volume and length of the gradual deceleration affecting safety through the analysis of variance,it suggests the gradual length value.The shortest safe deceleration distance calculation model is set up, and it suggestes safety length value of deceleration lane.Then, the drving test is carried out on the basis of drivers’ physiological characteristics. It establishes the composite indicator to represent drivers’ physiological characteristic by using principal component analysis (pca). According to the comprehensive index safety threshold, the paper establishes the logistic regression model of exit design index and driving operation safety, recommending the exit width and the wedge end ramp rate value.Finally, according to the standard and the safety recommendations made by the research, the two VISSIM simulation models are set up. Comparing the delay time and the number of conflicts, it verifies the validity of research results in this paper.Research results obtained in this paper have some reference value for design and safety evaluation of urban expressway in the future.