Optimization Of The Operational Schemes With Express/Local Trains On Regional Rail Transit

With the deepening of urbanization and the increasing of population,the scales of cities become larger and larger.Owing to the characteristics of large capacity,reliable punctuality and safety,urban rail transit systems are particularly important to metropolises to overcome traffic congestion problems and conduct the layout of the city.Regional rail transit connects the city center and suburbs,and the passenger flow shows the characteristic of imbalance because the lines usually have long distances.At the same time,express/local operation is an important method for regional rail transit,which aims at matching transport capacity and the imbalanced passenger demand,and improving both operational efficiency and service quality.Based on the analysis of existing research results,this paper summarizes practical express/local operation of regional rail transit at home and abroad,and studies the impact on the behavior of different passengers.Also,three optimization models of different express/local operation modes including equilibrium departure without overtaking,non-equilibrium departure without overtaking,and non-equilibrium departure with overtaking are proposed.Equilibrium departure means that the departure intervals at origion station are the same,and non-equilibrium departure means that the departure intervals at origion station can be different.Furthermore,the applicability for passenger demand and the feasibility of the three operation modes are analyzed.The main contents and conclusions are as follows:(1)Based on the types of passengers' origion and destination stations,the behavior under express/local operation of different types of passengers are analyzed.Taking into account of the constraints of carrying capacity,minimum departure frequency,and full-load ratio,a model aimed at minimizing passenger travel perception time and operational cost is proposed to optimize the departure frequencies of express and local trains and the skip-stop locations of express trains under the condition of equilibrium departure without overtaking.Then,a genetic algorithm is designed to solve the model,and a real case is taken as an example to prove the effectiveness of the method.The results show that compared with all-local operational scheme,express/local operational scheme can improve the speed of express trains by 5.0%,reduce passenger travel time by 1.6%and vehicle purchase cost by 2.4%with the same running distance,which means express/local operation can improve the profits of passengers and operator compared to all-local operational scheme.(2)Based on the optimization model under equilibrium departure without overtaking,a model under non-equilibrium departure without overtaking is proposed,which means the departure intervals at origion staion can be different,so departure intervals are added as decision variables.The results show that when departure frequency reduces under the same skip-stop scheme,vehicle purchase cost and running distance are reduced by 20%,while passenger travel time is increased by 4.0%,which means that appropriate reduction in departure frequency can reduce operational cost with little negative effect on passengers;compared with the mode of equilibrium departure,the mode of non-equilibrium departure under the same departure frequency can increase the maximum skip-stop number from 1 to 2,increase the travel speed of Express train increased by 5.0%,reduce passenger travel perception time by 2.2%under the comprehensive effect of an increase on waiting time and a decrease on in-vehicle time,and reduce vehicle purchase cost by 2.4%under the same running distance.Thus,express/local operation under non-equilibrium departure can improve the profits of passengers and operator than equilibrium departure.(3)Based on the optimization model under non-equilibrium departure without overtaking,a model with overtaking is proposed.Also,the locations of overtaking and departure intervals are added as decision variables.The results show that compared with the mode without overtaking,the mode with overtaking can increase the maximum skip-stop number from 2 to 4,increase the travel speed of express trains by 11.7%,reduce passenger travel perception time by 1.7%,slightly increase vehicle purchase cost by 0.8%under the same running distance.Thus,express/local operation with overtaking can improve the comprehensive profits of passengers and operator than operation without overtaking.(4)The applicability of the three express/local operation modes under different passenger demands is discussed based on the sensitive analysis of passenger demand.The effect of different express/local operation modes on passengers and operator are analyzed under different passenger demands and the corresponding departure frequencies.The results show that when passenger demand of the case reduces more than 10%,express/local operation under non-equilibrium departure without overtaking is optimal;when passenger demand of the case reduces less than 10%or increases less than 20%,express/local operation with overtaking is optimal;when passenger demand of the case increases more than 20%,all-local operation is optimal.Thus,express/local operation under non-equilibrium departure without overtaking is suitable to less passenger demand,express/local operation with overtaking is suitable to medium passenger demand,and all-local operation is suitable to larger passenger demand.(5)The feasibility of the three express/local operation modes is discussed based on the demands of different express/local operation modes for departure frequencies and departure intervals.The results show that when express/local operation mode changes from equilibrium departure to non-equilibrium departure,the marginal condition of express/local operation changes from departure frequency should be less than 16 columns/h to less than 20 trains/h;when express/local operation mode changes from no-overtaking to overtaking,the marginal condition of express/local operation changes from departure frequency should be less than 20 columns/h to less than 26 columns/h,which means the modes from equilibrium departure to non-equilibrium departure,and from no-overtaking to overtaking,gradually increase the feasibility of express/local operation.