Phd Dissertation

Stable Day-to-day Departure Time Dynamics at the Corridor and Network Levels: Models, Optimal Pricing, and Applications

Abstract

Traffic congestion continues to pose serious challenges in metropolitan areas, including travel delays, air pollution, noise, and increased accident risks. These impacts translate to substantial societal costs, with major U.S. cities experiencing billions of dollars in annual congestion-related losses. A prominent feature of congestion is its temporal concentration during peak periods, driven largely by travelers’ similar trip timing decisions, such as arriving at work by 9:00 AM. Shifting demand away from peak periods is thus a critical strategy for mitigating congestion. This dissertation addresses this issue by developing and analyzing stable day-to-day dynamical models of travelers’ departure time choices and examining how optimal pricing influences these decisions to improve system efficiency.While traditional transportation analyses focus on equilibrium outcomes, they often overlook the dynamic process by which such equilibria are achieved. This dissertation focuses on how travelers adjust their departure times from day to day and collectively converge to a departure time user equilibrium (DTUE). By capturing these dynamics, we can better design pricing policies that can drive the system toward a system optimal (SO) state. A major emphasis is on the theoretical stability of the dynamical models, which is essential to ensure that they reflect real-world travel behavior that is empirically observed to be convergent.This dissertation advances the field in four key areas. First, it extends an existing stable single-class day-to-day departure time dynamical model at the corridor level to a multi-class setting, with traveler heterogeneity. When desired arrival times are identical, with different queuing costs relative to unpunctuality costs, the proposed multi-class model is proven to be asymptotically stable, and its stationary state is equivalent to a multi-class DTUE. Second, it applies various pricing schemes to both single- and multi-class dynamical models. It is demonstrated, both theoretically and numerically, that appropriate pricing, such as optimal fine tolling, can drive the system from a DTUE to a stable, stationary SO state. Third, the dissertation extends departure time modeling from a single corridor to the network level using Vickrey’s cordon pricing framework with 48-hour entry data from Manhattan, New York. Results show that Vickrey’s marginal cost pricing — combined with day-to-day adjustments — can drive the system to a practically stable optimal state. Finally, the dissertation integrates the network-level departure time dynamics with dynamic traffic assignment (DTA) modeling. Results show that Vickrey’s marginal cost pricing significantly improves peak-period congestion, average speeds, vehicle miles traveled (VMT), and vehicle hours traveled (VHT). The work also explores the generalized bathtub model and develops insights on effectively reproducing DTA results at much less computational cost, offering a unique sketch-level dynamic planning method for large networks.In summary, the dissertation: (1) introduces the first provably stable multi-class day-to-day departure time dynamics; (2) shows that optimal pricing can drive both single- and multi-class systems to a stable SO state; (3) empirically validates Vickrey’s pricing in a real-world urban context; and (4) compares the effects of departure-time versus route-choice optimization using DTA. Collectively, these contributions provide a stable modeling framework for analyzing and managing departure time choices at both corridor and network levels, which offers new theoretical insights for designing congestion pricing policies, and provides practical insights on a notably more efficient process for transportation planning at large.

Suggested Citation
Siwei Hu (2025) Stable Day-to-day Departure Time Dynamics at the Corridor and Network Levels: Models, Optimal Pricing, and Applications. eScholarship, University of California. Available at: https://uci.primo.exlibrisgroup.com/permalink/01CDL_IRV_INST/u4evf/cdi_cdl_escholarship_oai_escholarship_org_ark_13030_qt5zr8s171.

published journal article

Association between Airport-Related Ultrafine Particles and Risk of Malignant Brain Cancer: A Multiethnic Cohort Study

Cancer Research

Publication Date

August 15, 2021

Author(s)

Anna H. Wu, Scott Fruin, Timothy V. Larson, Chiu-Chen Tseng, Jun Wu, Johnny Yang, Jennifer Jain, Salma Shariff-Marco, Pushkar P. Inamdar, Veronica W. Setiawan, Jacqueline Porcel, Daniel O. Stram, Loic Le Marchand, Beate Ritz, Iona Cheng

Abstract

Malignant brain cancer risk increases with airport-related UFP exposure, particularly among African Americans, suggesting UFP exposure may be a modifiable risk factor for malignant brain cancer.

Suggested Citation
Anna H. Wu, Scott Fruin, Timothy V. Larson, Chiu-Chen Tseng, Jun Wu, Juan Yang, Jennifer Jain, Salma Shariff-Marco, Pushkar P. Inamdar, Veronica W. Setiawan, Jacqueline Porcel, Daniel O. Stram, Loic Le Marchand, Beate Ritz and Iona Cheng (2021) “Association between Airport-Related Ultrafine Particles and Risk of Malignant Brain Cancer: A Multiethnic Cohort Study”, Cancer Research, 81(16), pp. 4360–4369. Available at: 10.1158/0008-5472.CAN-21-1138.

policy brief

Did COVID-19 Fundamentally Reshape Telecommuting in California?

Abstract

Health concerns and government restrictions during the COVID-19 pandemic caused a sharp increase in telecommuting (i.e., doing paid work at home or possibly an alternate worksite). In addition to reducing vehicle miles traveled (VMT), decreasing energy use, and lowering emissions of air pollutants and greenhouse gases (GHG), telecommuting may offer numerous other co-benefits, including increasing the worker pool, decreasing time and costs associated with travel, improving work-life balance, and decreasing stress. It may also stimulate greater use of non-motorized and active modes of travel (e.g., walking, biking, taking transit). However, telecommuting (especially during the pandemic) may also affect remote workers’ opportunities for promotion and ties with colleagues, health, work-life balance for families with children (childcare and schools did not operate normally during the pandemic), and even work productivity. It may also increase commuting length because telecommuters tend to live in more suburban areas, usually associated with fewer transit options and a higher likelihood of car use. While a large body of literature on telecommuting existed before COVID-191, this research looked at how the frequency of telecommuting changed in California during the pandemic, and how it may evolve. Whereas most previous research relied on non-random samples, the dataset used for this research was collected at the end of May 2021 by Ipsos, which randomly sampled Californian members of KnowledgePanel©, is the largest probability-based online panel in the nation, so the results are generalizable to California’s population. Quantifying changes in telecommuting is important for updating sustainable community strategies created by Metropolitan Transportation Organizations and gauging telecommuting’s likely contribution to meeting California’s GHG reduction targets. Moreover, analyzing telecommuting frequency for different socio-economic groups and occupations should help policymakers understand the long-term impacts of the pandemic on different segments of the labor market.

Suggested Citation
Md. Rabiul Islam and Jean-Daniel Saphores (2024) Did COVID-19 Fundamentally Reshape Telecommuting in California?. Policy Brief. UC ITS. Available at: https://doi.org/10.7922/g2z899rr.

published journal article

Adolescent Parental Monitoring Offers Protection Against Later Recurrent Driving After Drinking

Journal of Adolescent Health

Publication Date

August 1, 2024

Author(s)

Rebecca Schulte, Federico E. Vaca, Kaigang Li
Suggested Citation
Rebecca Schulte, Federico E. Vaca and Kaigang Li (2024) “Adolescent Parental Monitoring Offers Protection Against Later Recurrent Driving After Drinking”, Journal of Adolescent Health, 75(2), pp. 242–248. Available at: 10.1016/j.jadohealth.2024.03.011.

Phd Dissertation

Two essays on economics with applications in hypercongestion and bus transit

Abstract

Hypercongestion gives the problem of the non-unique relationship between travel time and flow in the fundamental diagram of traffic flow, which depicts the relationship between flow and density. Under the assumption of an exogenous time-pattern of demand and with the hypercongestion model in Small-Chu (1997), chapter one develops the backward iterative method in Vickrey (1991) to derive the marginal cost of additional entries at different times. The results show that the magnitude of the marginal external cost depends on not only the exogenously given entry rate but also the length of the entry period. With exogenous time pattern for demand, the marginal external cost of additional entry in the transportation system will increase to a peak from the beginning. Then it will decrease. During the [special characters omitted] entry period, the marginal cost curve is approximately symmetric. We can use policies, for example, staggering the work starting time, controlling the number of entry to change the entry time pattern to relieve the congestion. It has been noted that there is vicious cycle or virtuous cycle in production of transit services. However, few empirical researches have been done on transit service with consideration of this dynamic simultaneity. In chapter two, I will use dynamic simultaneous equations to model the dynamic simultaneous relationship between transit demand, transit supply and transit cost structure. The results show strong inertia in the bus demand, supply and cost. The response of supply level to the change of demand is consistent to the square root rule (Mohring 1972). This simultaneous model found much stronger scale economy in bus transit, both in short run and long run. The policy simulations show that the higher bus fare will decrease the ridership of bus at the very beginning. However, later on, the higher service brought by the higher revenue will offset the negative effect on ridership from higher bus fare. The operating deficit will decrease when higher bus fare is charged. Even though the favorable city characteristics could increase bus ridership and decrease the operating deficit at the same time, they are out of bus firm’s control.

Suggested Citation
He Wei (2003) Two essays on economics with applications in hypercongestion and bus transit. PhD Dissertation. UC Irvine. Available at: https://uci.primo.exlibrisgroup.com/permalink/01CDL_IRV_INST/1go3t9q/alma991035092916804701.

published journal article

Vulnerability of traffic control system under cyberattacks with falsified data

Transportation Research Record

Publication Date

March 1, 2018

Author(s)

Yiheng Feng, Shihong Huang, Qi Alfred Chen, Henry Liu, Z. Morley Mao

Abstract

Existing traffic control systems are mostly deployed in private wired networks. With the development of wireless technology, vehicles and infrastructure devices will be connected through wireless communications, which might open a new door for cyberattackers. It is still not clear what types of cyberattacks can be performed through infrastructure-to-infrastructure and vehicle-to-infrastructure communications, whether such attacks can introduce critical failure to the system, and what the impacts are of cyberattacks on traffic operations. This paper investigates the vulnerability of traffic control systems in a connected environment. Four typical elements, including signal controllers, vehicle detectors, roadside units, and onboard units, are identified as the attack surfaces. The paper mainly focuses on attacking actuated and adaptive signal control systems by sending falsified data, which is considered as an indirect but realistic attack approach. The objective of an attacker is to maximize system delay with constraints such as budget and attack intensity. Empirical results show that different attack scenarios result in significant differences in delay, and some ineffective attacks may even improve the system performance. Simulation results from a real-world corridor show that critical intersections, which have a higher impact on network performance, can be identified by analyzing the attack locations. Identification of such intersections can be helpful in designing a more resilient transportation network.

Suggested Citation
Yiheng Feng, Shihong Huang, Qi Alfred Chen, Henry X. Liu and Z. Morley Mao (2018) “Vulnerability of traffic control system under cyberattacks with falsified data”, Transportation Research Record, 2672(1), pp. 1–11. Available at: 10.1177/0361198118756885.

published journal article

A note on the determinants of metropolitan airline traffic

International Journal of Transport Economics / Rivista internazionale di economia dei trasporti

Publication Date

January 1, 1985

Author(s)

Suggested Citation
Jan K. Brueckner (1985) “A note on the determinants of metropolitan airline traffic”, International Journal of Transport Economics / Rivista internazionale di economia dei trasporti, 12(2), pp. 175–184. Available at: http://www.jstor.org/stable/42748169.

published journal article

Fine Particulate Matter, Its Constituents, and Spontaneous Preterm Birth

Obstetrical & Gynecological Survey

Publication Date

May 1, 2025

Author(s)

Anqi Jiao, Alexa N. Reilly, Tarik Benmarhnia, Yi Sun, Chantal Avila, Vicki Chiu, Jeff Slezak, David A. Sacks, John Molitor, Mengyi Li, Jiu-Chiuan Chen, Jun Wu, Darios Getahun

Abstract

(Abstracted from JAMA Network Open 2024;7(11):e2444593) Spontaneous preterm birth (sPTB) occurs following spontaneous labor or preterm premature rupture of membranes. It accounts for up to 70% of all preterm births (PTBs) and can result from infection or inflammation, decidual hemorrhage, uterine over distention, and chronic or acute stress.

Suggested Citation
Anqi Jiao, Alexa N. Reilly, Tarik Benmarhnia, Yi Sun, Chantal Avila, Vicki Chiu, Jeff Slezak, David A. Sacks, John Molitor, Mengyi Li, Jiu-Chiuan Chen, Jun Wu and Darios Getahun (2025) “Fine Particulate Matter, Its Constituents, and Spontaneous Preterm Birth”, Obstetrical & Gynecological Survey, 80(5), p. 278. Available at: 10.1097/01.ogx.0001113768.55844.6c.

conference paper

Experiments with computerized self-administrative activity survey

Travel patterns and behavior; effects of communications technology: Planning and administration

Publication Date

January 1, 2001

Author(s)

MS Lee, Michael McNally

Abstract

The process of activity scheduling is crucial to the understanding of travel behavior changes. In-depth research is urgently needed to unearth this process. A new computer program, REACT!, was developed to collect household activity scheduling data for this purpose. The program is implemented as a stand-alone program with Internet connectivity for remote data transmission. It also contains a geographic information system for location identification and a special feature that traces the decisions in the scheduling process. A pilot study was conducted in Irvine, California, to evaluate the program’s performance. Preliminary analysis validated the program’s capability of guiding participants to complete data entry tasks on their own; thus, the objective of reducing the cost of human resources for such a computerized survey is achieved. Other positive results were obtained regarding the objectives of reducing instrumental biases and expanding program capabilities. Areas for improvement were identified in the pilot study. On the basis of the findings, REACT! represents an ideal platform for a computerized household survey that can produce data for activity-based travel models.

Suggested Citation
MS Lee and MG McNally (2001) “Experiments with computerized self-administrative activity survey”, in Travel patterns and behavior; effects of communications technology: Planning and administration. TRANSPORTATION RESEARCH BOARD NATL RESEARCH COUNCIL / Transportat Res Board (Transportation research record), pp. 91–99.