Abstract
Transportation systems have been traditionally operated on a First-Come-First-Served (FCFS) fashion. FCFS consumption of supply occurs because it is accepted as a natural paradigm when the operators have no individual-specific information that allows consideration of any other serving order, and when users are assumed not to communicate among themselves. Thus, FCFS behaves as a status quo policy that is generally considered as fair, since it is presumed that all users are treated equally. We know though, that there exists heterogeneity in users’ valuation of time and delay savings, and that the values may be different in different situations even for the same user. Taking advantage of smartphones and connected vehicle environments, it is now possible to include this user heterogeneity into operations in order to increase overall system efficiency and fairness, where efficiency refers to satisfaction of users. There are then possibilities of accomplishing this through exchanges among users with appropriate pricing, which can be determined by the users themselves to their satisfaction, so as to determine the order and extent of the utilization of supply. This new operational paradigm leads to collaborative consumption of supply.
This dissertation explores the idea of violating FCFS by allowing users to trade in real-time the part of supply that they effectively “own” while they are in a transportation system. This de-facto ownership originates from the space-time region which each user rightfully controls, either due to their physical presence or due to reservations such as after purchasing a future trip from an operator. Attempting to answer the question of what pricing scheme would be fair and acceptable, leads this dissertation to introduce for the first time in transportation literature, the fundamental economic concept of envy-freeness. It can be taken as a pricing scheme as well as a user-behavior model. A resource allocation is said to be envy-free, when no agent feels any other agent’s allocation to be better than their own, at the current price. An extension called dynamic envy-freeness is then developed for use in the domain of dynamic problems that the transportation field invariable pose, and a new family of envy-minimizing criteria are developed, namely the Constant Elasticity of Substitution Envy Intensity (CESEI) criteria, which strongly fits into the existing axiomatic body of Welfare Economics.
Several applications of collaborative consumption that breaks FCFS ordering are explored in this dissertation. First, the dissertation develops PEXIC, Priced EXchanges in Intersection Control, in which users can pay other users to reduce their waiting delays in a fair manner. This system is shown to be Pareto-efficient, envy minimizing and financially self-sustainable. Second, it studies new operational policies in highway control: parallel queue routing policies for bottleneck situations where the vehicles’ lane-queue selections are the results of trades, and queue-jumping operations for exit lanes where vehicles can take forward spots in a queue by paying the overtaken vehicles in a fair fashion that achieves queue stability. Third, it proposes Peer-to-peer (P2P) ride exchange in ridesharing systems, in which trip property rights are transferred to users in such a way that they can trade their rides between each other. Finally, the dissertation models a P2P ridesharing system as a dual role market exchange economy, introducing a truthful pricing scheme which includes High-Occupancy-Vehicle (HOV) lane savings and uses a novel min-cost max flow formulation that guarantees users a ride-back, a complementarity in preferences never explored before.
The research does not attempt any elaborate examination of the social equity implications of such exchange-based systems with non-FCFS operations, but identifies some of such key issues and presents pointers for further study. It does not purport to take an advocacy position on transforming the transportation system operations to the newer paradigms, nor does it examine all the regulatory complications. The research does, however, demonstrate through modeling and analysis results from a variety of applications, that better system efficiency and user satisfaction can be achieved with the use of the proposed paradigms.
