Research on Optimization Method of Urban Rail Transit Operation Plan based on a Flexible Train Formation Strategy

In view of the circumstance of unbalanced spatial-temporal distributed passenger flow in urban rail transit, a new flexible train formation strategy based on virtually coupled train set (VCTS) is presented for enhancing the matching degree between capacity supply and passenger demand. Firstly, after the discussion of characteristics of the existing and the flexible train formation strategies, their adaptability to the unbalanced passenger demand is analyzed in order to emphasis the superiority of the new train formation strategy. Next, according to the presented new strategy, an integer nonlinear programming model adapted to unbalanced passenger flow is established, which can be solved efficiently by the controlled random search (CRS) algorithm. Finally, through a case study, the effectiveness of the proposed model is verified. The results indicate that the flexible train formation strategy has stronger adaptability to unbalanced passenger flow than the existing strategies, which can maximumly shorten the passenger waiting time by 25.1% and 21.6%, and reduce the number of required fleet size by 28.9% and 23.1% in peak and off-peak hour respectively.