research report

Drivers’ Responses to Eco-driving Applications: Effects on Fuel Consumption and Driving Safety

Abstract

Onboard eco-driving systems provide drivers with real-time information about their driving behavior and road conditions, encouraging them to optimize their driving speed and consequently reduce fuel consumption and emissions. However, there are barriers to making eco-driving a habit. To determine the elements that influence drivers’ intentions to practice eco-driving and their acceptance of eco-driving technology, the research team developed a theoretical model based on established theories on planned behavior, technology acceptance, and personal goals. The findings showed that drivers’ intention to practice eco-driving has an indirect effect on their intention to use the system via the factor of perceived ease of use. The research team also explored how cognitive distraction while using an eco-driving system can be a potential barrier to acceptance. The intent is to put forward a solution to improve drivers’ usage of eco-driving by turning off guidance when the system detects that the driver is experiencing serious distraction. To investigate how to detect a driver’s cognitive distraction status when they are interacting with an eco-driving system, this project used a driving simulator and leveraged machine learning algorithms to classify drivers’ attentional states. The findings showed that the glance features played a more important role than the driving features in cognitive distraction.

policy brief

Women Have Smaller Activity Spaces Than Men, Especially in Households with Children

Publication Date

September 3, 2025

Author(s)

Fariba Siddiq, Zhiyuan Yao, Evelyn Blumenberg

Abstract

Differences in how men and women travel have long been a focus in transportation research. Many studies have explored how socially-defined gender roles influence travel decisions and behaviors, consistently highlighting disparities between men’s and women’s travel patterns. For example, compared to men, women tend to make more caregiving and household-related trips, have shorter commutes, and are more likely to combine multiple destinations or purposes into a single tour. This body of research often concentrates on standard measures of travel—such as the number of trips taken, how far and for how long people travel, and travelers’ experiences— while also considering the influence of neighborhood design. However, travel patterns also are shaped by broader social structures and inequalities, which are not captured by these traditional measures. To better understand sex differences in travel, this study examined disparities in the size of an individual’s “activity spaces,” defined as the geographic area a person covers during daily activities, such as commuting, shopping, socializing, and leisure. The study draws on detailed trip data from the confidential California add-on to the 2017 National Household Travel Survey (NHTS), which provides the exact starting and ending locations for each trip taken on the survey day. The study estimates the size of each person’s activity space and compare patterns between men and women. It then explore how these differences relate to individual, household, and neighborhood characteristics.

policy brief

Advancing Community-Identified Strategies to Transform Roadways in California’s San Joaquin Valley

Abstract

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.

This publication describes how the research team evaluated opportunities and barriers to using a community steering committee process approach to advance environmental justice and transportation equity. Through interviews and case study analysis, the team examined the role community leaders played in the prioritization and implementation of three community-identified strategies that mitigate roadway hazards in three AB 617 communities in California’s San Joaquin Valley – Stockton, South Central Fresno, and Arvin/Lamont. These strategies include (1) vegetative barriers between roadways and sensitive land uses; (2) expanded sidewalk infrastructure; and (3) revised heavy duty truck route designations.

research report

Between the Forest and the Trees: Community Strategies to Transform Roadways in California’s San Joaquin Valley

Abstract

Expanding participation of historically disenfranchised groups within decision-making processes is an important strategy to increase equity within transportation planning but traditional engagement practices (e.g., public meetings, focus groups) have historically done little to address the needs of disadvantaged communities. This study evaluates the opportunities and barriers to using a community steering committee participation model within transportation planning to advance equity and environmental justice. It utilizes interview and case study analysis to examine the experiences of residents and community leaders in prioritizing community-identified strategies to mitigate roadway hazards in three AB 617 communities in California’s San Joaquin Valley – Stockton, South Central Fresno, and Arvin/Lamont. It investigates the role resident and CBO members played in the prioritization, approval, and implementation of three strategies to transform roadways and mitigate air pollution, noise, dust, and safety hazards: (1) new vegetative barriers between major roadways and sensitive land uses; (2) expanded sidewalk infrastructure; and (3) revised heavy-duty truck route designations. Findings demonstrate that “meaningful involvement” for impacted communities within transportation planning will require officials, residents, and organizations to commit to an ongoing process of experimentation and learning about the most effective approaches for advancing transportation equity and environmental justice.

policy brief

What Would it Take for Drivers to Adopt Eco-Driving Behaviors?

Abstract

Climate change in California could greatly impact the state’s economy, nature, and public health. One strategy to reduce fuel consumption and greenhouse gas emissions from the transportation sector is eco-driving. Eco-driving is a set of behaviors or driving styles that encourage fuel-efficient driving that could help minimize energy consumption anywhere from five to 30 percent. With the advance of connected-vehicle technologies, the dynamic eco-driving concept uses real-time vehicle-specific information to optimize vehicle speed and reduce fuel consumption and emissions.

This policy brief finds that driver motivations for adopting eco-driving behaviors varies, perceived ease of use was a key factor influencing a
driver’s intention to use an eco-driving system, and (3) based on the result of the driving simulator experiment, drivers may become distracted while trying to follow the information provided by the eco-driving interface.

research report

Headed Out Less: Analyzing Teen and Young Adult Travel Trends in the 21st Century

Publication Date

August 4, 2025

Author(s)

Andy Fung, Fariba Siddiq, Yu Hong Hwang, Brian D. Taylor

Abstract

Since the turn of the millennium, daily travel per person in the U.S. has been declining. Leading up to the pandemic, travel by older teens and young adults declined even more steeply than among older adults. After collapsing early in the pandemic, per capita travel by all ages has rebounded, but remains below pre-pandemic levels. To explore changes in personal travel, particularly among younger travelers, we examine National Household Travel Survey data from 2001, 2009, 2017, and 2022 to compare measures of everyday travel by youth (aged 15 to 29) with middle-aged adults (aged 30 to 59). The data presented in this report point to even lower levels of youth travel compared to pre-pandemic levels. Trips for all purposes have declined in absolute terms, especially for shopping/errands and, for youth in particular, social/recreational purposes. In relative terms, private vehicle use has increased, and travel by public transit and active modes has decreased. These shifts in personal travel – down overall and toward cars – suggest that pandemic-prompted travel shifts toward fewer out-of-home activities and increased use of information and communications technologies for shopping and other trips may be having enduring effects on personal travel, particularly among younger travelers.

Steering California’s Transportation Future: A Report on Possible Scenarios and Recommendations

Status

Complete

Project Timeline

January 19, 2022 - July 14, 2022

Principal Investigator

Project Team

Campus(es)

UCLA

Project Summary

What will California’s transportation and land use future look like? Will Californians gain more mobility and housing options that support the state’s economic, social, and climate goals? Or will the car continue to shape what cities look like and how people get around in them? These questions are important because how Californians live and move in the future will be shaped by investments and policies made today. In this project, the researchers investigated the future of transportation, land use, and planning in California by exploring four transportation/land use scenarios for 2050 with a panel of 18 experts. The four scenarios were: (1) more city living and lots of traffic, (2) easy to get around without a car, (3) you’ll need a car to get around, and (4) lots of travel choices, but most will drive. Their consensus opinion was that the most desirable scenario (“Easy to Get Around without a Car”) is also the least likely to materialize, due to faults in the political planning process. Despite promising state policies to increase transportation choices, problematic local land use politics and patterns appear likely to yield a future scenario (“Lots of Travel Choices, but Most Will Drive”) that continues car dependence and chronic congestion, absent a significant rebuilding of government trust and capacity.d

Evaluating Place-Based Transportation Plans

Status

Complete

Project Timeline

September 22, 2022 - September 30, 2023

Principal Investigator

Project Team

Campus(es)

UCLA

Project Summary

California has increasingly turned to place-based, community-driven programs such as Transformative Climate Communities (TCC), the Community Air Protection Program (CAPP), and Regional Climate Collaboratives (RCC) to address the twin priorities of climate change and environmental justice. Transportation improvements are at the heart of these programs because of the potential to mitigate air pollution, greenhouse gas emissions, and inequities in access to transportation. However, these efforts are inherently difficult to evaluate as they often involve a diverse set of projects with different timelines and locations. Moreover, evaluators often face the challenge of isolating the effects of individual programs. Carefully selected control sites can support this effort, but no two communities are exactly alike, limiting the ability of evaluators to make meaningful comparisons. This research addresses how place-based climate action efforts are being evaluated, and what insights from the broader policy and plan evaluation research literature might inform evaluation design. The focus is on place-based, community-driven programs in California that encompass multiple interventions to address intertwined issues of transportation justice, climate change, and air pollution. While TCC, RCC, CAPP, and the Sustainable Transportation Equity Project (STEP) are the most high-profile programs, the project will also consider planning grants such as Sustainable Communities Planning Grants and Community-Based Transportation Plans. For each funded program site the research team will review planning and evaluation documents and annual reports to compile a dataset of data collection and evaluation activities classified by (1) type of activity being assessed (planning vs. implementation), (2) evaluation indicator (e.g. air quality, transportation accessibility), (3) data source (e.g. interviews, air sensors), and program design (e.g. cross-sectional vs. longitudinal, inclusion of control sites). The research team will complement the review of these documents with 10-20 key informant interviews with staff from state and local agencies to help understand how the evaluations are proceeding in practice, and which aspects of place-based program evaluations have proved most valuable, challenging, and scalable to other programs.

New Methods for Integrating Traveler Constraints and Travel Demand Modeling

Status

Complete

Project Timeline

September 20, 2022 - March 31, 2025

Principal Investigator

Project Team

Tat Srisan

Campus(es)

UCLA

Project Summary

Advancing the tools needed for equity analysis of transportation investments requires new frameworks that consider the real world conditions of vulnerable communities and link to travel behavior analysis, transportation infrastructure, and policy assessment practices. Large-scale urban travel demand models (made up of a system of linked discrete choice models) are widely used to evaluate the costs and benefits of transportation investments and are employed during the transportation decision-making process. Yet, absent from this classic framework is the role that systematic constraints play in shaping opportunity spaces for certain travelers, which can skew assessments of transportation costs and benefits and drive inequitable and harmful transportation investments.

This research project will develop a methodological framework for extending travel demand modeling, to explicitly integrate constraints on traveler decision-making, such as racial and income disparities in access to travel alternatives. This framework requires new approaches of modeling traveler choice sets, and using non-traditional data sources, such as data on auto insurance premiums and auto loan availability. Developing methods to integrate such traveler constraints requires innovation in the measurement of latent effects that vary across communities and how best to associate these effects with the travel choice generation process.

The required research activities include a literature and data review, testing of measurement approaches and choice model structures for capturing traveler constraints, and performing a series of statistical and model checking tests, to arrive at clear recommendations for improvements in modeling practices.

Road Infrastructure Resilience Improvement for Wildfire Hazards

Status

In Progress

Project Timeline

February 3, 2025 - June 30, 2027

Principal Investigator

Project Summary

The recent wildfires in Los Angeles County have exposed severe vulnerabilities in the region’s road network, especially in hillside and canyon neighborhoods. These areas often feature circuitous, poorly connected street layouts with narrow roads and limited evacuation routes, creating dangerous bottlenecks during emergencies. In the January 2025 wildfires, gridlocked traffic at critical choke points forced residents to abandon vehicles, further complicating evacuation efforts and delaying emergency responders. These challenges underscore the urgent need to address inadequate street connectivity in wildfire-prone areas. Climate change-driven increases in wildfire frequency and intensity exacerbate these risks by raising the likelihood of extreme events that outpace current evacuation and response capabilities. Existing research on wildfire hazards often focuses on evacuation strategies or overall system resilience. Still, it rarely examines how street network design impacts evacuation efficiency and wildfire resilience at a network-wide scale. Furthermore, traditional risk-based approaches fail to consider cascading impacts on interconnected road systems

To tackle these issues, this project has initiated hyperlocal data collection in wildfire-affected regions of Los Angeles using a cutting-edge mobile mapping platform equipped with a Kaarta device. This system captures high-resolution LiDAR and panoramic imagery, enabling precise assessments of road widths, connectivity, and vulnerabilities in real-world conditions. By integrating wildfire simulation, connectivity analysis, and resilience assessment to prioritize retrofitting needs, this study will provide actionable recommendations for evacuation planning and infrastructure resilience in Los Angeles County.