Urban Rail Transit Line Timetable Optimization Base On Flexible Skip-Stop Scheme

With the rapid development of rail transit in the past 10 years,it is found that long-distance railway lines are becoming more and more prevalent.And the spatial and temporal imbalance of passenger flow along railway lines has also significantly increased.For this,recent research interests of urban rail transit have shifted to non-all-stop operation schemes.With the emerging technological advances in the acquisition of passenger flow data,and more attention has been paid to the applications of such data,non-all-stop operation is one of the immediate applications.As automatic driving of trains becomes increasingly available,the automatic implementation of non-all-stop train operation is becoming possible in real operation.Compared to the All-Stop Scheme(ASS),existing literature shows that the adoption of nonall-stop scheme is the only approach that can be applied to those lines where overtaking is not allowed-such as double-track line which is most commonly used in China and abroad.While skip-stop schemes lead to the in-vehicle travel time saving,one side effect of the schemes(e.g.,AB-station skip-stop)is the decline of line utilization.To address such side effect,this research proposes a Flexible Skip-Stop Scheme(FSSS)to optimize service quality and line capacity utilization.In this research,a FSSS optimization model is firstly constructed for single direction operation.Secondly,the safe and efficient train turnaround operation at the turnaround stations is taken into consideration,and bi-level FSSS train operation models are developed for bi-directional peak-hour and off-peak operations.The main constraints of the models can be characterized into two groups.The first group is the train departure interval constraint,which includes the train safety operation constraint,the departure interval constraint of the passenger flow demand,and the constraint for safe turnaround operation at the turnaround station.The second is the train operation strategy constraint,which includes the passenger accessibility constraint,and the passenger maximum waiting time constraint that ensures acceptable service level under FSSS.In addition,a train operation simulation model is established and heuristic algorithms are developed to efficiently solve the model.The results show that FSSS has better performance than ASS,both in peak and off-peak periods.Improvements are achieved in terms of passenger travel time and train speed.Explorations are also made to the following two problems in the research.(i)The tradeoff between passenger travel time and waiting time.Under FSSS,the passenger’s in-vehicle travel time can be saved by the skipping some stations,while for the passengers waiting on the skipped stations,the total passenger waiting time increased.That is,a tradeoff between passenger in-vehicle time and waiting time exists.A bi-objective optimization model is built to capture this tradeoff.(ii)The impact of passenger confusion rate on FSSS.It is assumed that certain percentage of passengers is confused by the FSSS scheme can fails to board the right train.The model takes these certain percentage of passengers into consideration is optimizated.Results show that as the passenger confusion rate increases,the impact on the system also increases and eventually stabilizes at some point.Overall,the proposed FSSS always has better system performance even at relatively high passenger confusion rate.