Research On Analysis Method Of Expressway Weaving Area Capacity

Weaving area is an important facility in the expressway system, which is used for vehicle lane switching. Given to the fact that the capacity of the weaving area is smaller than road section, level of service will decrease and congestion often occurs. This paper studied the capacity of the weaving area, in order to more accurately evaluate the weaving area level of service, design better geometry, and at the same time improve the operation efficiency and safety standard.Based on literature review of existing analysis methods, this thesis studied and compared the accuracy, feasibility, computation efficiency and implementation efficiency of the capacity analysis methodologies presented in ‘the ninth five-year’ capacity analysis manual, ‘the 11 th five-year’ capacity analysis manual, China highway capacity manual and US highway capacity manual 2010, recommended freeway weaving area traffic capacity analysis method.Despite HCM2010 breaks the limitation of physical length, presented a more logical, freer and clearer weaving area traffic capacity analysis method. Study result reveals that the methods in HCM 2010 are not subject to various limitations and have a high study value. Meanwhile, because of the lack of the impact of flow factors, the predicted speed in weaving area was found higher than non-weaving area. This is contradicted to the weaving area operation feature. Based on these findings, this thesis reorganizes and improves the model based on the data from the expressway-weaving area, which is proved to be more accurate through validation.Considering the fact that when traffic volume is high enough, speed becomes less sensitive to the change of volime, thus traffic density should be used as the factor for level of service evaluation, instead of speed. During evaluation process, it is difficult to measure the density, so as to evaluate the weaving area directly. Therefore, this thesis analized the traffic load degree(v/C) distribution under different density conditions, and found that the same density level can correspond to various load degree, and a same loading degree can correspond to various traffic density conditions. It is difficult to clearly distinguish the level of service for weaving area with one single index, the same goes to the description of boundary condition. In this thesis, traffic load degree is used as main factor and density is used as second main factor to provide a more detailed and better clarifies level of service categorization criteria.