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Autonomous Vehicles' Impact on Public Transit

The rapid advancement of autonomous vehicles technology in recent years has changed transport systems and consumer habits globally. As countries worldwide see a surge in the use of autonomous vehicles, the rise of shared autonomous mobility on demand (AMoD) service is likely to be next on the cards. Public transit, a critical component of urban transportation, will inevitably be impacted by the upcoming influx of AMoD and the question remains unanswered on whether AMoD would coexist with or threaten the public transit system.

Researchers at the Future Urban Mobility (FM) interdisciplinary research group at the Singapore–MIT Alliance for Research and Technology (SMART), MIT’s research enterprise in Singapore, and MIT conducted a case study in the first-mile mobility market from origins to subway stations in Tampines, Singapore, to find out.

In a paper titled “Competition between Shared Autonomous Vehicles and Public Transit: A Case Study in Singapore” recently published in Transportation Research Part C: Emerging Technologies, the first-of-its-kind study used game theory to analyze the competition between AMoD and public transit.

The study was simulated and evaluated from a competitive perspective ― where both AMoD and public transit operators are profit-oriented with dynamically adjustable supply strategies. Using an agent-based simulation, the competition process and system performance were evaluated from the standpoints of four stakeholders — the AMoD operator, the public transit operator, passengers, and the transport authority.

“The objective of our study is to envision cities of the future and to understand how competition between AMoD and public transit will impact the evolution of transportation systems,” says the corresponding author Jinhua Zhao, SMART FM lead principal investigator and associate professor in the MIT Department of Urban Studies and Planning. “Our study found that competition between AMoD and public transit can be favorable, leading to increased profits and system efficiency for both operators when compared to the status quo, while also benefiting the public and the transport authorities. However, the impact of the competition on passengers is uneven and authorities may be required to provide support for people who suffer from higher travel costs or longer travel times in terms of discounts or other feeder modes.”

The research found that the competition between AMoD and public transit would compel bus operators to reduce the frequency of inefficient routes and allow AMoDs to fill in the gaps in the service coverage. “Although the overall bus supply was reduced, the change was not uniform”, says Baichuan Mo, the first author of the paper and a PhD candidate at MIT. “We found that public transit services will be spatially concentrated to shorter routes that feed directly to the subway station, and temporally concentrated to peak hours. On average, this reduces travel time of passengers but increases travel costs. However, the generalized travel cost is reduced when incorporating the value of time.”

The study also found that providing subsidies to public transit services would result in a relatively higher supply, profit, and market share for public transit as compared to AMoD, and increased passenger generalized travel cost and total system passenger car equivalent, which is measured by the average vehicle load and the total vehicle kilometer traveled.

The findings suggest that public transit should be allowed to optimize its supply strategies under specific operation goals and constraints to improve efficiency. On the other hand, AMoD operations should be regulated to reduce detrimental system impacts, including limiting the number of licenses, operation time, and service areas, resulting in AMoD operating in a manner more complementary to a public transportation system.

“Our research shows that under the right conditions, an AMoD–[public transport] integrated transport system can effectively co-exist and complement each other, benefiting all four stakeholders involved,” says DUSP alum Hongmou Zhang (PhD '19), a SMART FM alumnus who is now assistant professor at Peking University School of Government. “Our findings will help the industry, policymakers, and government bodies create future policies and plans to maximize the efficiency and sustainability of transportation systems, as well as protect the social welfare of residents as passengers.”

The study is important for future mobility industries and relevant government bodies as it provides insight into possible evolutions and threats to urban transportation systems with the rise of autonomous vehicles and AMoD, and offers a predictive guide for future policy and regulation designs for a AMoD–public transit integrated transport system. Policymakers should consider the uneven social costs, such as increased travel costs or travel time, especially to vulnerable groups, by supporting and providing them with discounts or other feeder modes.

The research is carried out by SMART and supported by the National Research Foundation (NRF) Singapore under its Campus for Research Excellence And Technological Enterprise (CREATE) program.

FM harnesses new technological and institutional innovations to create the next generation of urban mobility systems to increase accessibility, equity, safety and environmental performance for the citizens and businesses of Singapore and other metropolitan areas worldwide. SMART-FM is supported by the NRF and situated in CREATE.

SMART was established by MIT and the NRF in 2007 to undertake cutting-edge research of interest to both parties. SMART currently comprises an Innovation Center and five interdisciplinary research groups: Antimicrobial Resistance, Critical Analytics for Manufacturing Personalized-Medicine, Disruptive and Sustainable Technologies for Agricultural Precision, FM, and Low Energy Electronic Systems.

 

Repost of the Singapore-MIT Alliance for Research and Technology's June 4th, 2021 MIT News piece.