Research On Flexible Concession Period Of PPP Rail Transit Project Based On Dynamic Buffer

In order to alleviate the huge financial pressure and improve the efficiency of project operation,the PPP model is being widely adopted in the field of rail transit.The scientific and reasonable setting of the concession period is an important prerequisite for the success of PPP rail transit projects.The concession period of traditional rail transit projects is generally determined directly by decision makers.But this method does not fully consider the impact of various uncertain factors in the future project operation on the concession period,and it is difficult to effectively utilize the advantages of PPP public-private cooperation and encourage social capital to improve project operation performance.Therefore,a reasonable flexible concession period model can not only effectively deal with various uncertain factors affecting the concession period,but also better inspire social capital to give full play to the advantages of technical management endowments,which has important theoretical and practical significance for the success of PPP rail transit project.In view of this,this paper proposes a study that is flexible concession period for PPP rail transit projects based on dynamic buffering according to the critical chain theory.The main research contents are as follows:(1)The definition of influencing factors of PPP rail transit project concession period.Twenty-four key influencing factors were identified from forty-seven uncertain factors affecting the concession period by using the method of questionnaire survey,and the six common factors and their weights on the concession period was obtained by using the factor analysis method;thirty-two main factors were identified from forty-eight factors affecting project performance,so the performance evaluation index system of PPP rail transit project was constructed.(2)The initial buffer model for flexible concession periods for PPP rail transit projects.Firstly,the basic operation period of the project was clarified by using the coupling net present value method and the data of the demonstration project.Next,in order to solve the problem of large scale and long periods of PPP rail transit project,and fully considering the impact of various uncertain factors on its concession period,the idea of setting a buffer in the critical chain project management theory CCPM was introduced to cope with this impact.Then,according to the characteristics of various factors influenced in the concession period on the degree of dynamic changes in the operating stage,drawing on the cut-and-paste method under the idea of variable rights,and considering the subjective weight of the influence of uncertain factors on the concession period,the coefficient of sensitivity and phase,the initial buffer model for flexible concession periods for PPP rail transit projects was built.(3)Dynamic management of buffer zone for flexible concession period of PPP rail transit project.Firstly,according to the relevant standards and existing research results of urban rail transit service quality and satisfaction evaluation,the PPP rail transit project performance evaluation index system was constructed from the aspects of equipment service,operation efficiency,safety capability,sustainability,operation energy consumption,operation cost and operation time.Then,according to the actual impact of these factors on project performance and buffer zone,a dynamic adjustment strategy of concession period buffer zone was introduced.Finally,after comparing the actual performance with the set threshold,through a mathematical model with rewards and punishments,the length of the buffer zone is dynamically managed to motivate social capital to take advantage of technical management.(4)Combining the proposed research method with the engineering example of the PPP rail transit project in K City,it is verified that the method can not only effectively deal with the influence of various uncertain factors on the calculation of the elastic concession period,but also can be used as an effective method for social capital.Incentives are more conducive to promoting the success of PPP rail transit projects,and also provide a theoretical basis for the government to scientifically decide the concession period.