A Heuristic Close Contact Tracing Method for Urban Rail Transit

In complex rail transit networks, there are always passengers whose trips are relatively fixed. These passengers can act as heuristic "witnesses" and prove the feasibility of a certain trip for other groups of passengers and help to identify potential close contacts with a guaranteed recall rate. This paper aims to develop a method to trace the close contacts in the urban rail transit system. A heuristic tree search method was used to form the feasible trip chains of target passengers by leveraging a limited number of witnesses. It could be determined whether the target passenger was a close contact by identifying whether there were any overlaps between the target trip chain and the infected trip chain. Taking Beijing urban rail transit as an example, volunteers were recruited to ride on specific lines and the information of infected persons was assumed for the study purpose. The effectiveness of the method was verified by extracting relevant Automatic Fare Collection (AFC) data to identify close contacts. In the experimental scenario, the recall rate reached 100% and the accuracy rate was 92.7% using the proposed method, indicating the feasibility of the method. The proposed method is helpful for the relevant department to take appropriate countermeasures to prevent the spread and transmission of the epidemic. © 2022 Science Press. All rights reserved.