Design and Operation of Efficient and Budget-Balanced Shared-Use Mobility Systems

University Transportation Centers Programhttps://dx.doi.org/10.7302/10552021PDFTech ReportMasoud, NedaTafreshian, AmirmahdiCenter for Connected and Automated Transportation (CCAT)University of Michigan, Ann ArborUnited States. Department of Transportation. University Transportation Centers (UTC) ProgramUnited States. Department of Transportation. Office of the Assistant Secretary for Research and TechnologyUniversity of Michigan. Center for Connected and Automated TransportationUnited StatesCommutersIncentivesShared mobilitySubsidiesTravel behaviorCCAT Project Number 1269A3551747105Final Report (March 2018-March 2021)Traffic congestion has become a serious issue around the globe, partly owing to single-occupancy commuter trips. Ridesharing can present a suitable alternative for serving commuter trips. However, there are several important obstacles that impede ridesharing systems from becoming a viable mode of transportation, including the lack of a guarantee for a ride back home as well as the difficulty of obtaining a critical mass of participants. This paper addresses these obstacles by introducing a Traveler Incentive Program (TIP) to promote community-based ridesharing with a ride-back home guarantee among commuters. The TIP program allocates incentives to (1) directly subsidize a select set of ridesharing rides, and (2) encourage a few, carefully selected set of travelers to change their travel behavior (i.e., departure or arrival times). The authors formulate the underlying ride-matching problem as a budget-constrained min-cost flow problem, and present a Lagrangian Relaxation-based algorithm with a worst-case optimality bound to solve large-scale instances of this problem in polynomial time. The authors further propose a polynomial-time budget-balanced version of the problem. Numerical experiments suggest that allocating subsidies to change travel behavior is significantly more beneficial than directly subsidizing rides. Furthermore, using a flat tax rate as low as 1% can double the system's social welfare in the budget-balanced variant of the incentive program.127