Reducing an urban rail transit network's passenger-oriented vulnerability by adding turn-back tracks

The links between two adjacent turn-back stations in an Urban Rail Transit Network (URT) are defined as an Interaction Link Set (ILS), and any link interruption in an ILS renders unusable all links in the ILS. The percent decrease in Total Passenger Trips (T-trips), percent increase in Travel Time Per Trip (P-time) and percent increase in the Number of Transfers Per Trip (P-trans), respectively, due to ILS interruption, measure the Passenger-Oriented Vulnerability (POV) of a URT in terms of travel feasibility, travel time and travel convenience. The sum of the length-weighted percent increases in Travel Cost Per Trip (P-cost) for each ILS interruption comprehensively measures a URT's POV. Models are proposed for minimizing a URT's POV by adding Turn-Back Tracks (TBs) at stations in an optimized sequence. An application demonstrates that the models can identify which stations should receive TBs according to what priority for effectively reducing the POV.