A study of open payment fare systems : system design, fare engine algorithm and GTFS extension

Abstract

This thesis describes the design and implementation of the key parts of an open payment system that supports mobile phone ticketing for the Long Island Railroad (LIRR), a part of the New York Metropolitan Transportation Authority (MTA). While many public transit agencies across the world are still using traditional fare systems, open payment system can help reduce lifecycle costs for transit agencies while making public transit service more convenient to passengers. One of the keys to the implementation of an open payment fare system is to infer trips and compute fares from a series of taps on gates and fareboxes by an open payment device, either a bankcard or a mobile phone. A trip construction algorithm based on a finite state machine is proposed to automatically group tap events from a single user into trip segments according to the MTA's fare rules and send them to a fare engine for fare calculation. The trip construction algorithm (implemented in the trip server) can handle bus, subway and railroad tap events in the MTA's system with fraud detection and exception handling. The fare engine adapts a label-correcting shortest path algorithm to find the chosen paths for each trip segment and to calculate the fare based on the LIRR's fare structure, including a number of configuration parameters such as minimum fare, minimum transfers and minimum travel time. The shortest path algorithm runs on a directed graph that is capable of modeling LIRR's complex service and transfer restrictions. Recognizing the limitations of system-specific fare engine design, this thesis also proposes extensions to the General Transit Feed Specification (GTFS), and develops a generic fare engine design that can be shared across multiple transit systems. These extended designs are studied and tested on the LIRR and Transport for London (TfL) networks. The proposed design appears to accommodate the fare policies of many transit systems; eight systems are briefly reviewed.