|Competition between Shared Autonomous Vehicles and Public Transit: A Case Study in Singapore
|Year of Publication
|Baichuan Mo, Zhejing Cao, Hongmou Zhang, Yu Shen, Jinhua Zhao
|Transportation Research Part C
Emerging autonomous vehicles (AV) can either supplement the public transportation (PT) system or compete with it. This study examines the competitive perspective where both AV and PT operators are proﬁt-oriented with dynamic adjustable supply strategies under ﬁve regulatory structures regarding whether the AV operator is allowed to change the ﬂeet size and whether the PT operator is allowed to adjust headway. Four out of the ﬁve scenarios are constrained competition while the other one focuses on unconstrained competition to ﬁnd the Nash Equilibrium. We evaluate the competition process as well as the system performance from the standpoints of four stakeholders—the AV operator, the PT operator, passengers, and the transport authority. We also examine the impact of PT subsidies on the competition results including both demand-based and supply-based subsidies. A heuristic algorithm is proposed to update supply strategies for AV and PT based on the operators’ historical actions and proﬁts. An agent-based simulation model is implemented in the ﬁrst-mile scenario in Tampines, Singapore. We ﬁnd that the competition can result in higher proﬁts and higher system eﬃciency for both operators compared to the status quo. After the supply updates, the PT services are spatially concentrated to shorter routes feeding directly to the subway station and temporally concentrated to peak hours. On average, the competition reduces the travel time of passengers but increases their travel costs. Nonetheless, the generalized travel cost is reduced when incorporating the value of time. With respect to the system eﬃciency, the bus supply adjustment increases the average vehicle load and reduces the total vehicle kilometer traveled measured by the passenger car equivalent (PCE), while the AV supply adjustment does the opposite. The results suggest that PT should be allowed to optimize its supply strategies under speciﬁc operation goals and constraints, and AV operations should be regulated to reduce their system impacts, including potentially limiting the number of licenses, operation time, and service areas, which makes AV operate in a manner more complementary to the PT system. Providing subsidies to PT results in higher PT supply, proﬁt, and market share, lower AV supply, proﬁt, and market share, and increased passengers generalized cost and total system PCE.