Impact Of Train Overtaking At Stations On Capacity And Operational Efficiency Of Urban Rail Transit Lines

As the urban population grows,the city expands outwards,and the urban rail transit lines gradually extend outwards from the city center.The local trains can no longer meet the diverse travel demands of passengers.The operation of the express/local trains can better adapt to the uneven characteristics of passenger flows,improve the travel efficiency of long-distance passengers,accelerate the turnover of trains,save the number of trains,and improve the efficiency of urban rail transit.But at the same time,the operation of express/local trains has some drawbacks,which is necessary to be further studied.The main work and conclusions are as follows:(1)Based on research on the concept of express/local trains,types,operating conditions,calculation principles of line capacity,and typical domestic and foreign cases,there is a summary of the applicability evaluation index for express/local trains,according to line conditions and passenger flow conditions.And the adverse effects of express/local trains transportation organization mode on increasing the waiting time of local trains and reducing line capacities are analyzed.It provides theoretical support for constructing the optimization model of line operation efficiency with overtaking.(2)By analyzing the operation process of trains at overtaking stations,we establish a quantitative model of the waiting time of local trains at overtaking stations.Then the factors affecting the waiting time of local trains at overtaking stations and the compression strategy are analyzed.We build a simulation model of express/local trains operation by python and carry out a case study.The case study shows that increasing the speed of express trains,increasing the distance between the front and rear stations of the overtaking station,reducing the departure interval at the station before the overtaking station,and increasing the limited speed of the station can shorten the waiting time of local trains at the overtaking station.(3)Study the influence of express train overtaking at stations on capacities.We summary the formula for calculating line capacities under the different proportions of express/local trains and times of express trains overtaking.The influence of parameters such as the ratio of express and local trains,the quantity of overtaking,the speed difference,the number of skip-stop stations,the overtaking location,and the stop time on the line capacity is analyzed.The case study shows that the strategies such as increasing the proportion of trains of the same type,reducing the number of skip-stop stations,narrowing the gap between the number of skip-stop stations before and after overtaking,and shortening the dwell time can improving line capacities.(4)This paper studies the total travel time of passengers and the composition of enterprise cost.Under the scenario of single routing,single formation,and given ratio of express and local trains,considering the influence of different operation ratio,overtaking position,overtaking times,and number of skip-stop stations on the line capacity,a comprehensive operation efficiency optimization model is constructed,which aims to minimize the passenger and enterprise cost.Besides,the decision variables of the model are local train departure frequency,express train departure frequency,express train stop sequence,and overtaking position.Finally,we design a genetic algorithm to solve the model.(5)An urban rail transit line in S city is taken as an example to verify the validity of this model,and the optimal express/local trains operation plan is solved.In the case of the same total frequency,compared with the only local trains,the total travel time of passengers is saved by 6,103 minutes,which is reduced by 0.49%,in which the total dwell time is reduced by 28.87%;the total cost of the enterprise is reduced by 8172 yuan,which is reduced by 6.34%,in which the cost of stopping at stations is reduced by 20.83%.Besides,the cost of purchasing vehicles is reduced by 5.18%.Additionally,the influence mechanism of factors such as the ratio of express and local trains,the speed difference,the number of skip-stop stations,the location of overtaking,and the dwell time as well as maximum train load factor and passenger flow volume on the efficiency of line operation is studied.Then strategies of reducing the adverse impact of train overtaking on operation are proposed.