Calculation Method for the Reasonable Length of Underground Ring Road Weaving Segment
The development of underground ring roads has become a new initiative to relieve traffic pressure in the urban core.In order to optimize the design of the underground ring road,the reasonable length of the weaving segment was studied with capacity and traffic simulation analysis.Firstly,considering several influencing factors,the calculation method for the length of underground ring road weaving segment was constructed,and each parameter was calibrated.Secondly,taking the underground ring road in the T5 station business district of Airport New City of Xi Xian New Area as an example,the results of Vissim simulation before and after the construction of underground ring road were compared,as well as the traffic conflicts between the original project design and the design obtained by the proposed method through Surrogate Safety Assessment Model(SSAM).Finally,the recommended value of the length of underground ring road weaving segment under general conditions was given.The results show that:a)the length obtained by the calculation method has a small error(less than 4.2％)with the simulation results,which proves that the proposed method could calculate the length efficiently;b)compared with the original design,the traffic conflict rate is reduced by 73.2％,which testifies that the length obtained by the method is more reasonable;c)with the construction of the underground ring road,the travel time is reduced by 39.6％maximum,the delay is shortened to within 2 s,and the maximum decrease of queue length is 88.1 m,which indicates that the construction of the underground ring road could improve the level of service using the calculation method.The design based on the proposed method can improve the traffic safety of the underground ring road and reduce the congestion in the urban core.
traffic engineeringunderground ring roadthe capacity of weaving segmentthe length of weaving segmenttraffic simulation
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