LegalFarePlan Optimizes Urban Rail Routes with Non-Additive Fares.

A novel route-planning framework, LegalFarePlan, has been developed to address the complexities of urban rail systems with non-additive fare structures. In many transit networks, the total fare for a journey might not simply be the sum of individual leg fares, especially when legal exit-and-reentry operations are involved. LegalFarePlan explicitly models these operations as auditable constraints, ensuring fare transparency in route calculations. The framework takes into account various parameters, including the transit network layout, fare functions, transfer rules, station-level exit/re-entry costs, an extra-time budget, and a split limit. It then computes explainable route plans segmented by paid journeys. Evaluation on a semi-synthetic benchmark demonstrated that the bounded exact search method within LegalFarePlan identified positive fare reductions for a significant portion of origin-destination pairs, showcasing its potential to optimize routes for cost-efficiency while maintaining transparency.