Informal and Privatized Transit: Incentives, Efficiency and Coordination

Informal and privatized transit services, such as minibuses and shared auto-rickshaws, are integral to daily travel in large urban metropolises, providing affordable commutes where a formal public transport system is inadequate and other options are unaffordable. Despite the crucial role that these services play in meeting mobility needs, governments often do not account for these services or their underlying incentives when planning transit systems, which can significantly compromise system efficiency. Against this backdrop, we develop a framework to analyze the incentives underlying informal and privatized transit systems, while proposing mechanisms to guide public transit operation and incentive design when a substantial share of mobility is provided by such profit-driven private operators. We introduce a novel, analytically tractable game-theoretic model of a fully privatized informal transit system with a fixed menu of routes, in which profit-maximizing informal operators (drivers) decide where to provide service and cost-minimizing commuters (riders) decide whether to use these services. Within this framework, we establish tight price of anarchy bounds which demonstrate that decentralized, profit-maximizing driver behavior can lead to bounded yet substantial losses in cumulative driver profit and rider demand served. We further show that these performance losses can be mitigated through targeted interventions, including Stackelberg routing mechanisms in which a modest share of drivers are centrally controlled, reflecting environments where informal operators coexist with public transit, and cross-subsidization schemes that use route-specific tolls or subsidies to incentivize drivers to operate on particular routes. Finally, we reinforce these findings through numerical experiments based on a real-world informal transit system in Nalasopara, India.