28 DEC 2023 (THUR) | 14:00-15:00

Markov Decision Processes in Shared Mobility Operation Problems

Speaker:

Dr. Zheng Zhu

Department of Civil Engineering, Zhejiang University, China

Date:    December 28, 2023 (Thursday)

Time:   2:00-3:00 pm

Venue:  Room 612B, 6/F Haking Wong Building, The University of Hong Kong

Abstract

The supply-demand imbalance of shared mobility (e.g., ride-sourcing and bike-sharing) is one critical factor that leads to passenger queueing and congestion, idle ride-sourcing vehicles, accumulation of shared bikes, low public transit ridership, and high-level travel costs, so that it restricts the mobility efficiency and social welfare of urban transportation systems. Designing spatial-temporal operation strategies (e.g., pricing, (e)bike rebalancing/recharging, ride-sourcing idle vehicle relocation) can be a feasible approach for mitigating the imbalance. However, concerning the coupling mechanism among supply, demand, and operational strategies, it is difficult to seek smart spatial-temporal strategies via conventional modeling and optimization approaches. Recently, with Markov decision processes (MDPs) and reinforcement learning (RL) have received increasing attention, which have the capability of formulating and solving dynamic optimization problems in complex environments. In this presentation, we show several MDPs the research team has developed for depicting and solving spatial-temporal operational problems in the shared mobility market. Aiming at developing smarter shared mobility systems, we would share our knowledge and experiences for a better understanding of similar problems.

About the Speaker

Zheng Zhu, “Hundred Talents Program” Professor, Assistant Head of Department of Civil Engineering at Zhejiang University. Research interests include the planning, design, simulation, management/control and optimization of multi-modal transportation systems. From 2008 to 2021, Zheng has been studying and working at Tsinghua University, University of Maryland, Hong Kong University of Science. He is the principal investigator of 1 Hong Kong Research Grants Committee General Research Fund (RGC-GRF), the participant of 1 Major Research Plan of China National Natural Science Foundation. Zheng has participated in research projects funded by many agencies, such as the US department of transportation (USDOT), the US department of energy (USDOE), US National Science Foundation (NSF), US Federal Highway Administration (FHWA), Aspiration Zealous Force Trustworthy (AZFT), Smart Urban Future (SURF) Laboratory, Zhejiang Province. He has published over 50 SCI papers in top transportation journals such as IEEE TITS, TR Part B, POM, TR Part C, and TR Part E. Zheng serves as the area editor in the annual meeting of the Chinese Overseas Transportation Association (COTA) and an editorial board member in Transportation Safety and Environment.

Hosts:

DEPARTMENT OF CIVIL ENGINEERING

JOINTLY ORGANIZED WITH 

HONG KONG SOCIETY FOR TRANSPORTATION STUDIES

And INSTITUTE OF TRANSPORT STUDIES, HKU

09 NOV 2023 (THUR) | 10:00-11:00

Integrated optimization of bus bridging service design and passenger assignment in response to urban rail transit disruptions

Associate Prof. Yu Zhou

School of Transportation Science and Engineering, Beihang University, China

Date: November 9, 2023 (Thursday)

Time: 10:00am – 11:00am

Venue: Room 612B, 6/F Haking Wong Building, The University of Hong Kong

Abstract

As the urban rail transit (URT) system plays an increasingly important role in supporting large cities' mobility around the world, service disruptions have become more prevalent, potentially resulting in severe economic losses and passenger safety issues. It is imperative to investigate effective response strategies to mitigate the effects of such disruptions. In response to URT service disruptions, this paper systematically investigates the bus bridging service design (BBSD) problem, which concerns the integration of bus bridging route design, frequency determination, and passenger assignment in the integrated URT and bus network. The problem is formulated as a path-based integer linear programming (ILP) model with the goal of simultaneously minimizing operator-oriented and passenger-oriented costs. A column generation-based approach is proposed to solve this model efficiently, allowing nonintuitive bus routes to be freely generated on the network dynamically. Our method has been tested with two different case studies based on real data from the Hong Kong Mass Transit Railway (MTR). Experiments demonstrate that our proposed approach can assist public transit (PT) operators in developing efficient emergency response plans for various potential disruption situations in advance. Even in the face of unexpected disruptions that necessitate a quick response, our approach can generate high-quality solutions in a matter of minutes.

About the Speaker

Dr. Yu Zhou is about to join the School of Transportation Science and Engineering, Beihang University as an associate professor. Dr. Zhou’s research interests include (i) public transportation operations and management, (ii) future mobility and (iii) multimodal transportation. Dr. Zhou dedicated his research efforts to addressing fundamental and cutting-edge issues in the field of transportation. His rigorous studies have culminated in the publication of over 30 papers in internationally renowned SCI journals and academic conferences. Notably, Dr. Zhou has taken the lead role, as either the first or corresponding author, in publishing 14 papers in prestigious SCI-indexed journals, including Transportation Research Part B, Part C, Part D, European Journal of Operational Research and Applied Energy. Beyond his published work, Dr. Zhou has actively contributed to the discourse within the global transportation community. He serves as the editorial member of Digital Transportation and Safety. In addition, Dr. Zhou has also been invited to peer review for over ten international journals and top-tier transportation conferences. These include but are not limited to Transportation Science, Transportation Research Part B, Part C, Part D, Part E, Accident Analysis and Prevention, and Computers & Operations Research. He is also a reviewer for prestigious conferences in the transportation field, like the International Symposium on Transportation and Traffic Theory (ISTTT) and TRB meetings.

Hosts:

DEPARTMENT OF CIVIL ENGINEERING

JOINTLY ORGANIZED WITH

HONG KONG SOCIETY FOR TRANSPORTATION STUDIES

And INSTITUTE OF TRANSPORT STUDIES, HKU

29 SEP 2023 (TUE) | 10:00 – 11:00

Using AVs to Replace Buses & Complement Urban Rail Systems

SPEAKER Professor Kara Kockelman Dewitt Greer Centennial Professor of Transportation Engineering Department of Civil, Architectural and Environmental Engineering The University of Texas at Austin ​ DATE AND TIME September 29 (Friday) 10:00 – 11:00 am (Hong Kong Time) REGISTRATION Please register by using this link: https://forms.office.com/r/xiT9c9E9xL Confirmation emails with ZOOM link will be sent to participants before the lecture. This Distinguished Transport Lecture will be held on ZOOM only. ORGANISED BY Institute of Transport Studies, The University of Hong Kong ​ ABSTRACT Motivated by shared autonomous vehicles’ (SAVs’) many potential services (like door-to-door [D2D] service, first-mile last-mile [FMLM] service, and bus replacements), this work explores traveler choices for different US settings, simulates fleets of SAVs in concert with other fixed-route transit, and analyzes results for travelers, their networks, and their regions. The presentation first microsimulates how SAVs can provide FMLM service to (and from) 5 commuter rail stations in central Austin neighborhoods. With train headways of 15 minutes, simulations predict dramatic increases in train use (by roughly a factor of 10, at those stations). Variations in train headways and SAV fleet sizes illustrate how D2D travel remains the key predictor of mode choice. Four-seat SAVs perform similarly to 6-seat SAVs, but cost less to provide. A dynamic ride-sharing (DRS) (vehicle-to-passenger assignment) algorithm tightly coordinated with train arrivals delivers 87% of travelers to their stations in time to catch the next train, while uncoordinated assignments deliver just 57% in time. Second, this work simulates 10-seat SAVs providing fixed-route transit service alongside private automobiles. System costs for each traveler type along a 6.4-kilometer (4-mile) corridor are computed across different SAV-use rates. The work prices out walking, waiting, riding, and driving times for all travelers in the corridor, along with vehicle ownership, parking, and operating costs. Results suggest that such self-driving mini-buses or 10-seat SAVs lower total costs per passenger-kilometer traveled when SAV mode split exceeds 30 percent, even though walking and waiting are valued at a relatively high cost. Third, a POLARIS-based mesoscopic simulation integrates three SAV service types across the 20-county Chicago region. When SAVs with DRS serve only D2D trips, at just $0.50 per passenger-mile, with 1 SAV for every 40 residents, they attract 15% of trips (and private vehicle ownership falls from 0.66 to 0.37 cars per capita), with a 15-minute average travel time and 4.6-mile average person-trip distance. Adding FMLM service (to about 54,000 train and bus stops) increases the region’s transit split: from 5.4% to 6.3% of travelers, with the same SAV fleet serving 12% more person-trip requests per day and driving 4.2% more SAV-miles. Most FMLM person-trip distances are under 2 miles, with rail-station connections dominating (rather than those to bus stations). Overall, many metro regions of the globe and their transit systems seem ready to benefit from SAV services. SPEAKER’S BIO Prof. Kara Kockelman is a registered professional engineer and holds a PhD, MS, and BS in civil engineering, a master’s in city planning, and a minor in economics from the University of California at Berkeley. She has been a professor of transportation engineering at the University of Texas at Austin for 25 years, and is the recipient of an NSF CAREER Award, Google Research Award, MIT Technology Review Top 100 Innovators Award, Vulog’s Top 20 of 2020 Influential Women in Mobility, and various ASCE, NARSC, TRF, and WTS awards. She recently served as President of the North American Regional Science Association and sits on the Eno Center for Transportation’s Advisory Board, as well as 3 TRB Committees. She has authored over 200 journal articles (and two books), and her primary research interests include planning for shared and autonomous vehicle systems, the statistical modeling of urban systems, energy and climate issues, the economic impacts of transport policy, and crash occurrence and consequences. Pre-prints of these articles (and book contents) can be found at www.caee.utexas.edu/prof/kockelman. She hopes you will join the zero-cost, zero-carbon Bridging Transportation Researchers conference (held in August each year), by submitting papers in spring & then registering here: www.bridgingtransport.org.