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.

preprint journal article

Optimal Fare Policy and Fleet Sizing for an Integrated Fixed-Route Transit and Microtransit System

Abstract

Integrating microtransit with fixed-route transit (FRT) can improve travelers’ mobility by leveraging the benefits of microtransit’s flexibility and FRT’s high passenger capacity. However, the high operating cost of microtransit presents a challenge, which calls for a careful evaluation of the trade-offs between mobility gains and operational cost. To address this need, this paper develops a modeling approach and solution procedure to identify Pareto-optimal designs. The researchers focus on design parameters of practical interest, namely, fare policies and microtransit fleet size. To explore these trade-offs, a bi-level and bi-objective (i.e., minimize taxpayer subsidy and maximize mobility-based consumer welfare) modeling framework, with an agent-based transportation system simulation model at the lower level and a multi-objective Bayesian Optimization (BO) model at the upper level is proposed. The research team applied the modeling and solution approach to Lemon Grove, California (a suburban area in San Diego County). Results revealed a diverse set of solutions along the Pareto frontier, indicating that some naive microtransit fare strategies are suboptimal. Notably, Pareto-optimal designs feature a 50-100% discount for microtransit to FRT transfers, as well as peak-period fare multipliers between 1.8x and 3.5x to manage time-varying demand effectively.

preprint journal article

Flexible Agent-based Modeling Framework to Evaluate Integrated Microtransit and Fixed-route Transit Designs: Mode Choice, Supernetworks, and Fleet Simulation

Publication Date

May 29, 2024

Author(s)

Siwei Hu, Michael Hyland, Ritun Saha, Jacob Berkel, Geoffrey Vander Veen

Abstract

The integration of traditional fixed-route transit (FRT) and more flexible microtransit has been touted as a means of improving mobility and access to opportunity, increasing transit ridership, and promoting environmental sustainability. To help evaluate integrated FRT and microtransit public transit (PT) system (henceforth “integrated fixed-flex PT system”) designs, the research team proposes a high-fidelity modeling framework that provides reliable estimates for a wide range of (i) performance metrics and (ii) integrated fixed-flex PT system designs. The researchers formulate the mode choice equilibrium problem as a fixed-point problem wherein microtransit demand is a function of microtransit performance, and microtransit performance depends on microtransit demand. The team proposes a detailed agent-based simulation modeling framework that includes (i) a binary logit mode choice model (private auto vs. transit), (ii) a supernetwork-based model and pathfinding algorithm for multi-modal transit path choice where the supernetwork includes pedestrian, FRT, and microtransit layers, (iii) a detailed mobility-on-demand fleet simulator called FleetPy to model the supply-demand dynamics of the microtransit service. This paper illustrates the capabilities of the modeling framework by analyzing integrated fixed-flex PT system designs that vary the following design parameters: FRT frequencies and microtransit fleet size, service region structure, virtual stop coverage, and operating hours. The research includes case studies in downtown San Diego and Lemon Grove, California. The computational results show that the proposed modeling framework converges to a mode choice equilibrium. Moreover, the scenario results imply that introducing a new microtransit service decreases FRT ridership and requires additional subsidies, but it significantly increases job accessibility and slightly reduces total VMT.

conference paper

Accessibility of Shared Automated Vehicles for the Visually Impaired Travelers

Abstract

In this study, the researchers conducted semi-structured interviews with 15 visually impaired individuals. The research team first explored their perspectives regarding their current travel behaviors and transportation experience. The research team then explored the potential of using Shared Automated Vehicles (SAVs) to enhance their travel experiences and address their existing transportation challenges. Results of the first part of the study revealed that most participants primarily worked from home, while those who commute largely relied on public transit. For doctor’s appointments, rideshare was the most common method of transportation followed by public transit and riding with family. Ridesharing also emerged as the dominant mode of transportation for other essential activities such as visiting family, socializing, attending events, or work-related travel. Results of the second part of the study revealed a range of expectations and concerns related to SAVs, particularly in the areas of accessibility, safety, communication, and affordability. Most participants expressed enthusiasm for the potential benefits of SAVs to increase independence and access to underserved areas. They also highlighted critical accessibility needs, such as reliable means to identify assigned vehicles, accurate drop-off locations, and accessible interfaces. Affordability emerged as the key factor influencing potential adoption, with many participants indicating a preference for SAVs if they were priced competitively with existing transportation options, especially in comparison with traditional rideshare services. Findings of this study provide valuable insights for policymakers, transportation planners, and SAV developers to ensure that future automated transportation solutions are fully inclusive and meet the diverse needs of all visually impaired travelers.

policy brief

How is Climate Change Affecting Landslide Susceptibility in California?

Abstract

Environmental shifts resulting from climate change have led to increased risk of natural hazards such as drought, wildfires, floods, and landslides, which all represent major threats to the state’s infrastructure. One particular risk that is posed by greater precipitation in areas affected by wildfires, which can lead to an increase in landslide hazard. There is little research available for predicting future landslide susceptibility. To address this gap, the research team developed a landslide susceptibility assessment framework which reflects changing climate conditions under different levels of projected greenhouse gas emissions and applied it to assess the vulnerability of California’s transportation infrastructure.

policy brief

Shared Automated Vehicles Could Greatly Benefit Visually Impaired Travelers if Designed and Operated with Their Needs in Mind

Abstract

Automated vehicles (AVs) are one of the most significant technological advances in transportation. The benefits of AV technologies could be maximized by increasing vehicle occupancy through pooling and ridesharing, integrating AV use with high-capacity transit systems (e.g., using AVs to complement existing transit), and promoting multimodality (e.g., connecting travelers to public transit). Additionally, shared automated vehicles (SAVs), in which ridesharing companies (similar as today’s Uber or Lyft) offer driverless on-demand mobility services to customers, could enhance transportation access for visually impaired travelers who face unique challenges navigating current transportation systems including public transit and rideshare services. To this point, the research team interviewed 15 visually impaired individuals to understand their current transportation experience (e.g., what challenges they face and how they cope with these challenges); how SAVs might address their transportation needs and challenges; potential issues and solutions for using SAVs; how their travel behavior may change due to SAVs; and how much they would pay for SAV rides.

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.