Optimization On Train Timetable For Urban Rail Transit Considering The Occupation Of Turn-back Route

In recent years,the frequency of headway of China’s urban rail transit lines is much higher than before with the increasing demand for passenger flow.Dense train services put forward higher requirements for the turn-back efficiency of turn-back stations.As an important node of the line in operation,the turn-back capability of turn-back stations directly affects the service level of the whole line.From the perspective of operation,this paper optimizes the occupation duration and assignment of trains’ routes inside the turnback stations in the process of traditional train timetable compilation.The main contents of this paper are as follows:(1)By analyzing the current operation status of domestic urban rail transit lines,the significance of this research is explained.Also,this paper summarizes the research results of domestic and foreign literature on the optimization of train timetable,calculation of turn-back capacity and train routing assignment.The research direction and innovation of this paper are clarified.(2)Taking the typical station types that trains turn back in front of and behind the platform as the research object,the turn-back process of different modes and the computation of turn-back intervals are summarized.The bottleneck of turn-back in special operation mode is analyzed as well.Based on the turn-back principle and cumulative 0-1 variables,the mathematical model of turn-back operation is constructed for these typical turn-back stations.(3)The optimization models of train timetable considering the occupation of turnback route under the operation modes of full-length and short-turn routing and express/local trains are constructed respectively.The former model takes the maximizing line capacity as the objective,comprehensively considering all kinds of constraints related to train operation and connection.The arrival and departure times,headway and turnback route of each train at different stations are optimized simultaneously.The latter model aims at maximizing the line capacity and minimum turn-back buffer time.The arrival and departure times of express and local trains at each station and each track inside the turn-back stations are calculated by reasonably adjusting the headway and overtaking pattern between the express and local trains.In addition,the solver and genetic algorithm are used to solve the two models respectively.The effectiveness of the model and algorithm is verified by small-scale examples.(4)Taking the virtual line as the background,the cases are designed and analyzed.In the full-length and short-turn routing operation mode,it is verified that the advantage of the model considering the occupation of turn-back route is to fully compress the buffer time of turn-back intervals and improve the turn-back capacity of the stations.The influence of layouts of turn-back stations on the line capacity is discussed.And the influence of the headway change of short-turn trains on the connection between trains at turn-back stations is analyzed when the proportion of short-turn trains is larger.In the express/local operation mode,this paper mainly compares the line capacity and train connection under the conditions of different ratios of the express/local trains and different rolling stock utilization.Results of the cases not only prove the high applicability of the models,but also provide some suggestions for providing efficient and safe train services under special operation modes.