Tradable credit scheme for mobility management: state of the art and comparison of theoretical and experimental research

A Tradable Credit Scheme for mobility management (TCS) represents a cutting-edge instrument to manage the transport demand and combat traffic congestion. In a TCS, a central authority, such as a municipality, distributes a certain number of credits to potential travellers within a network and charges them credit-based tariffs according to their mobility choices; travellers who save credits can profit by selling their unused credits to other travellers. Compared to other demand management strategies, such as pricing or odd–even plate rationing schemes, TCSs can be more equity-oriented and more likely to be accepted by public opinion, putting them under the research community's focus in the last decade. In this regard, numerous TCS design frameworks have been proposed. Moreover, first experiments have been conducted, assessing the effectiveness of TCSs in practice and bringing the TCS concept closer to real-world application, though full-scale implementation is yet to be realized. In the present review we thoroughly examine all the elements and actors of a TCS, and re-evaluate the research efforts in light of recent experiments. A wide variety of assumptions and design decisions emerged from the literature, revealing tendencies in terms of role of the Central Authority, user characterization, network considered, charging and allocation strategies, and market type. At the same time, gaps were identified in relation to user identification, behavioural response, allocation frequency, and credit trading. Finally, the comparison between experimental and theoretical studies showed differences in terms of network considered, demand representation, charging strategy and credit market.