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.

翻译：非正式与私营化交通服务（如小型巴士和共享电动三轮车）是大型都市日常出行的重要组成部分，在正规公共交通系统不足且其他出行方式难以负担时，提供了经济实惠的通勤选择。尽管这些服务在满足出行需求方面发挥着关键作用，但政府在规划交通系统时往往忽视这些服务及其内在激励，这可能严重损害系统效率。在此背景下，我们构建了一个分析框架，用以研究非正式与私营化交通系统的激励结构，并提出在营利性私营运营商承担主要出行服务时指导公共交通运营与激励设计的机制。我们引入了一个新颖且可解析的博弈论模型，描述具有固定线路菜单的完全私营化非正式交通系统，其中利润最大化的非正式运营商（驾驶员）决定服务区域，而成本最小化的通勤者（乘客）决定是否使用这些服务。在此框架内，我们建立了严格的无政府状态代价界限，证明去中心化的利润最大化驾驶员行为可能导致累计驾驶员利润与满足乘客需求方面产生有限但显著的损失。我们进一步表明，通过针对性干预措施可缓解这些性能损失，包括：采用斯塔克尔伯格路由机制（使少量驾驶员受中央调控，以反映非正式运营商与公共交通共存的场景），以及实施跨线路补贴方案（通过特定线路收费或补贴激励驾驶员运营特定线路）。最后，我们基于印度纳拉索帕拉的真实非正式交通系统进行数值实验，验证了上述结论。