Research On The Identification Of The Accident-prone Position For The Large Longitudinal Slope Of Xinjiang Wuyu Expressway And Traffic Security Guarantee Measures

With the promoting of policies of China's western region development and the Belt and Road Initiative,the focus of China's expressway construction has been transferred to central and western mountainous regions day by day.Because the geographic and geomorphic conditions there are more complex than plain regions,road sections of long and great longitudinal gradient in mountainous regions account for a large proportion of the expressways.While characteristics such as great elevation differences,harsh climatic condition and great difficulty of vehicle operation arrangement result in a sharp increase in operation risk of road sections with long and great longitudinal gradient,with frequent accidents occurring,therefore,it has become a problem required to be solved urgently as to how to guarantee traffic safety of road sections with long and great longitudinal gradient.Although a great number of practice and research have been carried out at home and abroad on traffic safety guarantee of road sections with long and great longitudinal gradient,they are not systematic enough.Particularly,the study on identification of locations prone to accidents is rare.Therefore,it is necessary to carry out studies on identifying locations prone to accidents of road sections with long and great longitudinal gradient of the expressway and on traffic safety guarantee measures,to provide technical support for sustained and healthy development of the expressway in China.This paper conducts research on traffic safety of large longitudinal slope sections.It takes design documents for Urumchi-Yuli expressway as the research object,evaluate travelling safety of large longitudinal slope sections based on operation speed and linear parameter,puts forward a set of identification techniques for accident black spots on large longitudinal slope sections based on braking temperature prediction and driving simulation technology which can give out a set of scientific and efficient safety assurance measures with comprehensive consideration on the influence on traffic safety caused by the synergistic effect among man,vehicle and road.Main research works of the paper are as following:First,by investigation and analysis on large longitudinal slope sections of the typical expressway in Sinkiang region – Urumchi–Sailimu expressway,accident mechanism for large longitudinal slope sections is revealed;then,methods such as theoretical analysis areapplied to analyze the influence of cold highland area environment on traveling safety on large longitudinal slope sections,thus to lay a foundation for follow-up researches.Secondary,the traveling safety evaluation method for large longitudinal slope sections based on design indexes is researched.Traveling safety of large longitudinal slope sections of Urumchi – Yuli expressway is evaluated by taking linear parameters such as horizontal radius,stopping sight distance and resultant gradient as evaluation indexes,as well as comparing design values and limiting values of linear parameters,verifying the coordination between measured values of operation speeds for adjacent road sections.Then,accident black spots on large longitudinal slope sections are identified by braking temperature prediction and driving simulation test.Taking braking temperature as index,physical model and energy conservation model are built respectively to calculate temperature distribution characteristics of brake under the braking mode of exhaust braking and unassisted braking;by taking wheel path deviation and safe driving speed as indexes,as well as applying of driving simulation technique based on eight degree of freedom simulation platform,tests of passing sections with different gradients and line forms in different speeds are designed to analyze the influence on wheel path caused by change of curve radius,and then return to analyze relationship between travel speed and gradient,thus to give out safe speed for longitudinal slope sections in various line forms.Based on the above,accident black spots on large longitudinal slope sections of Urumchi –Yuli expressway are identified accurately.Finally,advantages,disadvantages and adaptations of traffic safety precautions for multiple similar large longitudinal slope sections of expressways all over the country are investigated and analyzed.By comprehensive use of the above research achievements,a set of safety precautions suitable for Urumchi-Yuli expressway in Sinkiang is put forward.Research results of this paper can provide theoretical support for design,operation management and system monitoring for expressways in cold highland areas,as well as to lay foundation for construction of traffic safety guarantee system.