Research On The Method Of Setting The Left Hard Shoulder Of Super Multi-lane Highway

As an important part of a super multi-lane highway with wide cross-section and complex traffic organization,the left hard shoulder can provide emergency space for accident or breakdown vehicles to avoid secondary accidents,and can also be used as a temporary lane when the road section is congested due to accidents or construction to improve the traffic capacity of the road section.The research on the reasonable setting method of the left hard shoulder is essential to improve the safety and flexibility of the super multi-lane highway.In this study,the influencing factors of the setting of the left hard shoulder were extracted by collecting the design data and accident data of super multi-lane highways at home and abroad.The data related to each influencing factor of foreign super multi-lane highways equipped with left hard shoulder were collected,and after Z-score standardization,the influence weights of each factor were determined by using principal component analysis to explore the correlation between each parameter of super multi-lane highways and the setting of left hard shoulder,and thus the conditions for setting left hard shoulder were proposed.The UC-win road software was used to construct two kinds of two-way ten-lane highway simulation scenarios with closed and open left hard shoulder,and a driving simulator was implanted to conduct driving simulation experiments with different widths of the left hard shoulder.During the experiments,vehicle operation parameters were collected,including lateral offset,speed,transverse swing angular velocity and other data,and the significant influence of the left hard shoulder width on vehicle driving stability was proved by ANOVA analysis of variance.The results of the mean and standard deviation show that the vehicle driving parameters perform best when the width of the left hard shoulder is 3m.Therefore,it is recommended that the recommended value of the left hard shoulder width for a two-way ten-lane highway is 3m.The length of the common super multi-lane highway section was selected as the research object,and the two-way ten-lane highway scenario with different continuous length intermittent left hard shoulder continuous deployment was constructed by UC-win road software,and the driving simulator was implanted to carry out the left hard shoulder continuous length comparison driving simulation experiment,and the speed and lateral offset parameters of the vehicle were collected during the experiment.The speed results show that as the continuous length of the left hard shoulder increases,the speed change process gradually tends to level off,but the performance is most satisfactory when the continuous length is 5km.The results of lateral offset show that the vehicle gradually shifts to the left side of the lane as the continuous length of the shoulder increases,and the vehicle is closest to the center of the lane when the continuous length is 10 km,but the overall lateral offset corresponding to 10 km length is not significantly different from 5km and 15 km.Therefore,considering the analysis results of speed and lateral offset,the proposed range of continuous length of intermittent left hard shoulder of two-way ten-lane highway is about 5km.Taking the scenario of congestion on the road section caused by an accident as an example,the Van Aerde traffic wave model under the influence of the accident is established based on the Van Aerde traffic flow model,combined with the transmission mechanism of traffic waves after the accident.Based on the traffic flow characteristics of the super multi-lane highway with the implementation of left hard shoulder guidance measures at different time nodes,the type and change characteristics of the traffic waves generated after the accident are analyzed to derive the accident impact area of the super multi-lane highway and further derive the traffic queue length caused by the accident.The accident impact area is divided into four consecutive induced areas according to the functionality,and the length range of different induced areas is calculated,and the layer induced strategy related to the dynamic use of the left hard shoulder of the super multilane highway is formulated.The geometry size,setting conditions and induction method of the left hard shoulder proposed in this paper enriches the research on the setting method of the left hard shoulder of the super multilane highway and provides a reference basis for the setting of the left hard shoulder.The dynamic induction strategy of the left hard shoulder can provide theoretical support for developing the left hard shoulder opening strategy and inducing vehicle diversion measures when accidents occur.