Category: Research in Motion

Author: Pearce, Jeannine Marie; Ulibarri, Nicola, PhD; Borowski, Elisa, PhD

Institute of Transportation Studies, University of California, Irvine

At ITS-Irvine, researchers are exploring how environmental justice (EJ) can be more fully integrated into transportation, climate, and hazard preparedness planning. This study looks at how overlapping layers of governance in Greater Los Angeles—from city to regional to state—can both help and hinder progress toward equity-centered planning.

For decades, urban planning decisions such as redlining and freeway construction have divided neighborhoods and placed communities of color closer to pollution and other environmental risks. While efforts to include EJ principles in public policy have grown, they often remain scattered across agencies and plans rather than connected through a shared framework.

By reviewing 16 regional plans focused on climate action, racial equity, transportation, and hazard preparedness, the researchers assess how each addresses the core EJ values of recognition, participation, and fairness in outcomes. Their findings point to the need for stronger coordination and intentional planning across all levels of government to ensure every community benefits equally from investments in safety, mobility, and sustainability.

Key Research Findings 

• Recognition Justice is Inconsistent Across Plans
• Multi-Level Governance (MLG) Increases Coordination and Capacity, but EJ Remains Underemphasized
• Community Engagement is Correlated with Equity Integration in Planning
• Social Movements are Associated with Equity Integration as EJ in Planning Increases Post-2019

Author: Wenlong Jin and Joseph Lo

Institute of Transportation Studies, University of California, Irvine

At ITS-Irvine, researchers are pioneering innovative methods that balance the power of data with the need to protect individual privacy. In this study, Dr. Wen-Long Jin and Joseph Lo explores how a “bathtub model” can serve as a privacy-preserving alternative to traditional traffic data collection. Transportation agencies depend on detailed trip data to improve roads and transit systems, yet conventional and “big data” methods often track travelers’ movements with concerning precision—raising ethical and legal challenges under growing privacy regulations.

The bathtub model offers a fresh, system-level approach that captures the overall flow of trips across a network without identifying individual travelers. By representing travel based on the remaining distance rather than specific routes, the model enables meaningful insights into network performance while keeping personal data anonymous. This work demonstrates that it’s possible to advance transportation planning and analytics without compromising public trust or individual privacy.

Key Research Findings 

• The bathtub model effectively captures network traffic dynamics while preserving traveler privacy
• The bathtub model was successfully validated using public bike-sharing data
• Computational needs are low, enabling rapid assessments

Author: Wenlong Jin

Institute of Transportation Studies, University of California, Irvine

At ITS-Irvine, researchers are advancing the science of automated vehicle safety to ensure a smoother transition toward mixed human-autonomous traffic. In this study, Dr. Wenlong Jin addresses a critical gap in how automated vehicles (AVs) interpret and respond to real-world driving conditions. Current car-following models often fail to mimic the nuanced braking and spacing behaviors of human drivers, leading to potential safety and traffic-flow issues—especially at intersections designed for human decision-making.

To overcome this challenge, Dr. Wenlong Jin developed a multi-phase projection-based model that allows AVs to anticipate future braking scenarios rather than simply react to present conditions. This approach produces driving patterns that are both safer and more human-like, reducing the likelihood of “dilemma zones” and improving coordination between AVs and traditional vehicles. The work provides an essential step toward ensuring that automated vehicles can coexist harmoniously with human drivers and the infrastructure shaping California’s transportation future.

Key Research Findings 

• Standard car-following models have significant limitations in maintaining safe distances between vehicles in everyday driving situations
• Human drivers are able to anticipate when other vehicles may brake, but existing car-following models fail to adequately do this
• Our car-following model mathematically guarantees safety while exhibiting human-like behavior
• The model can be readily installed in AV systems

Farzana Khatun, PhD; Jean-Daniel Saphores, PhD.
Institute of Transportation Studies, University of California, Irvine

Bus ridership in many U.S. cities has declined over the past decade, and understanding the causes is vital for improving public transit systems. In Orange County, factors like poor service quality, low connectivity, competition from ride-hailing services, and changing socioeconomic conditions have all been cited as potential contributors. One lesser-explored factor is the implementation of Assembly Bill 60 (AB 60) in 2015, which allowed undocumented residents in California to obtain driver’s licenses.

At ITS-Irvine, our faculty are advancing transportation policy research by identifying how legislation and social trends affect transit behavior. In this study, Dr. Farzana Khatun and Dr. Jean-Daniel Saphores analyzed whether the introduction of AB 60 contributed to declines in OCTA bus ridership. Using route-level panel regression models and ridership data from 2014–2016, they found that local and community routes experienced significant ridership declines—up to 7.7% in Fall 2015–16—after AB 60 was implemented. The findings suggest that expanded access to driver’s licenses may have encouraged a shift away from public transit. To address these trends, the authors recommend that OCTA explore service adjustments, increased frequency, and free or discounted fare programs.

Key Research Findings:

• Gasoline prices also impacted bus boardings.
• After the implementation of AB 60, bus boardings decreased more than before.
• Route frequency did not matter in 2014-2016.
• Rail vehicle revenue hours (VRH) and peak hour frequency had a significant impact on bus boardings on local and community routes.

Authors: Khatun, Farzana, PhD; Saphores, Jean-Daniel, PhD.

Institute of Transportation Studies, University of California, Irvine

Bus ridership in many U.S. cities has declined over the past decade, and understanding the causes is vital for improving public transit systems. In Orange County, factors like poor service quality, low connectivity, competition from ride-hailing services, and changing socioeconomic conditions have all been cited as potential contributors. One lesser-explored factor is the implementation of Assembly Bill 60 (AB 60) in 2015, which allowed undocumented residents in California to obtain driver’s licenses. 

At ITS-Irvine, our faculty are advancing transportation policy research by identifying how legislation and social trends affect transit behavior. In this study, Dr. Farzana Khatun and Dr. Jean-Daniel Saphores analyzed whether the introduction of AB 60 contributed to declines in OCTA bus ridership. Using route-level panel regression models and ridership data from 2014–2016, they found that local and community routes experienced significant ridership declines—up to 7.7% in Fall 2015–16—after AB 60 was implemented. The findings suggest that expanded access to driver’s licenses may have encouraged a shift away from public transit. To address these trends, the authors recommend that OCTA explore service adjustments, increased frequency, and free or discounted fare programs.

Key Research Findings:

• After the implementation of AB 60, bus boardings decreased more than before. 
• Route frequency did not matter in 2014-2016. 
• Rail vehicle revenue hours (VRH) and peak hour frequency had a significant impact on bus boardings on local and community routes. 
• Gasoline prices also impacted bus boardings. 

Stay connected with ITS-Irvine for more insights on mobility innovation. To learn more, read the policy brief or explore the full report here.

Douglas Houston, Gregg P. Macey, Jeannine M. Pearce, Catherine Garoupa
Institute of Transportation Studies, University of California, Irvine

Disparities in exposure to roadway hazards (e.g., pollution, noise) remain stubbornly persistent due to structural inequalities embedded in the built environment. Research has consistently documented racial/ethnic and socioeconomic disparities in traffic exposures nationwide, including heightened exposure to heavy-duty truck traffic, a significant source of noise and pollution. Such disparities also exist in the provision of sidewalks, bike lanes, and street trees, which can help mitigate roadway dust, noise, and pollution and can increase pedestrian safety, encourage walking and cycling, and provide health benefits. These environmental injustices are tied to historic patterns of racial segregation and disinvestment. Traditional public engagement methods have largely failed to address these inequities.

At ITS-Irvine, our faculty are committed to advancing equity in transportation systems through community-engaged research. In this study, Dr. Douglas Houston, along with Gregg P. Macey, Jeannine M. Pearce, and Catherine Garoupa, evaluated the use of Community Steering Committees (CSCs) as an alternative engagement model in three AB 617-designated communities in California’s San Joaquin Valley—Stockton, South Central Fresno, and Arvin/Lamont. Through interviews and case study analysis, the research examined how residents and community leaders prioritized and implemented three local strategies to reduce roadway hazards: vegetative barriers, expanded sidewalk infrastructure, and revised truck routes.

Key Research Findings

• AB 617 Community Steering Committees (CSCs) expanded resident participation in decision-making.
• Resident frustration was common.
• Community-identified strategies were often delayed.
• Community-identified strategies were often implemented as short-term demonstration projects.