Safety Analysis On The Interchange Exit Ramp Of Mountainous Urban Road

There is generally a low alignment index,insufficient sight distance,short interwoven section,high transportation density,complicated-running traffic flow and multi-traffic conflict points on interchange exit ramp of mountainous urban road.The driver has to handle all types of information in a short time,visual and mental load increased significantly when vehicles running on exit ramp area,leading to frequent traffic accidents.According to analyze driver's visual characteristics and traffic safety analysis of interchange exit ramp on mountainous urban road,we can determine the safety level of each section of the interchange exit ramp area and provide a reference for the planning and design of the interchange exit ramp of mountainous urban road.Firstly,through an access to literature,the pilot questionnaire as well as a traffic survey of some typical interchange in Chongqing,analyze and derive the causes of the accidents,the traffic safety factors of interchange exit ramp of mountainous urban road,and derive geometry data of the exit ramp,provide the basis for the construction of visual load forecasting model and safety evaluation of interchange exit ramp on mountainous urban road.Secondly,describes the driver's vision theory and data analysis methods,conducted an actual vehicle eye test on interchange exit ramp of mountainous urban road to obtain driver's visual data,analyze the distribution of the driver's viewpoint using the frame statistics and accordingly divided the driver gaze region;statistical analyze the eye movement parameters such as regional number of fixations,fixation duration,,the pupil area change rate of the driver and the horizontal rotation angular mean velocity of the driver's head and so on,then conclude driver's interest region and gaze characteristic change rule in interchange exit ramp.Then,selecting the horizontal rotation angular mean velocity of the driver's head as the visual load evaluation index of interchange exit ramp on mountainous urban road.;using K-S test and Pearson correlation coefficient method to make a correlation test between the radius of ramp,deceleration lane length,rotation longitudinal slope of ramp,operating speed and the horizontal rotation angular mean velocity of the driver's head;constructed an visual load forecasting model of interchange exit ramp based on radius of ramp,deceleration lane length,rotation longitudinal slope of ramp,operating speed through driver's viewing angle,and verify the reliability of the model.Finally,selecting the horizontal rotation angular mean velocity of the driver's head as the safety index of interchange exit ramp;using 3? principle which set in the statistical to determine load visual comfort threshold and safety threshold,and divide visual load into low visual load,moderate visual load and high visual load,analyzes vehicle running safety of each section of the test interchange exit ramp area,and determine the dangerous sections;the visual load forecasting model of the exit ramp was put into an example of the application;combining visual load threshold,the horizontal rotation angular mean velocity of the driver's head and the relationship between various influencing parameters,some recommendations was put forward from the alignment design of the exit ramp and ramp design speed angle.