published journal article

A Deep-Learning Approach to Detect and Classify Heavy-Duty Trucks in Satellite Images

Publication Date

August 29, 2024

Author(s)

Xingwei Liu, Yiqiao Li, Langting Sizemore, Xiaohui Xie, Jun Wu

Areas of Expertise

Freight, Logistics, & Supply Chain Intelligent Transportation Systems, Emerging Technologies, & Big Data

Abstract

Heavy-duty trucks serve as the backbone of the supply chain and have a tremendous effect on the economy. However, they severely impact the environment and public health. This study presents a novel truck detection framework by combining satellite imagery with Geographic Information System (GIS)-based OpenStreetMap data to capture the distribution of heavy-duty trucks and shipping containers in both on-road and off-road locations with extensive spatial coverage. The framework involves modifying the CenterNet detection algorithm to detect randomly oriented trucks in satellite images and enhancing the model through ensembling with Mask RCNN, a segmentation-based algorithm. GIS information refines and improves the model’s prediction results. Applied to part of Southern California, including the Port of Los Angeles and Long Beach, the framework helps assess the environmental impact of heavy-duty trucks in port-adjacent communities and understand truck density patterns along major freight corridors. This research has implications for policy, practice, and future research.

research report

Road Capacity as a Fundamental Determinant of Vehicle Travel

Publication Date

February 1, 2025

Author(s)

Adam Millard-Ball, Michael Rosen

Areas of Expertise

Infrastructure Delivery, Operations, & Resilience Travel Behavior, Land Use, & the Built Environment

Abstract

Reducing vehicle miles traveled (VMT) is a central plank of climate policy in California. VMT, however, has proved stubbornly resistant to policies to reduce it. While urban growth has become more compact and public transit service levels have been maintained or increased, these positive trends have not translated into less driving. This report argues that substantial reductions in vehicle travel in congested urban regions can only be achieved through reducing road capacity. It may be difficult to achieve substantial reductions in vehicle travel by relying solely on public transit, walking and cycling, and land use planning for compact, mixed-use development without an equal emphasis on limiting road capacity expansions, and even reducing current capacity.

policy brief

Automobile Debt Increased Substantially during the Pandemic

Publication Date

January 1, 2025

Author(s)

Evelyn Blumenberg, Samuel Speroni, Fariba Siddiq, Jacob Wasserman

Areas of Expertise

Safety, Public Health, & Mobility Justice

Abstract

Most car buyers use some form of financing to purchase a vehicle, and almost half of all California borrowers carry some amount of automobile debt. While automobile loans enable lower-income households—who might otherwise be priced out of vehicle ownership—to make payments over time, this debt can significantly strain household budgets. The COVID-19 pandemic elevated the importance of owning a private vehicle as concerns over viral person-to-person transmission made traveling by car an even more attractive compared to communal transportation (e.g., public transit). Moreover, a host of pandemic-related services, including testing and vaccination, were either only or best accessible by car.

To better understand how COVID-19 impacted car ownership, this research project explored whether automobile loans (and in turn debt) in California—particularly in communities of color where workers were more likely to work outside of the home—increased during the pandemic. It drew on a one-percent sample of the University of California Consumer Credit Panel, a dataset from Experian of every loan and borrower in California.

policy brief

Road Expansion is the Fundamental Cause of Growth in Vehicle Travel

Publication Date

February 1, 2025

Author(s)

Adam Millard-Ball, Michael Rosen

Areas of Expertise

Infrastructure Delivery, Operations, & Resilience Travel Behavior, Land Use, & the Built Environment

Abstract

California is unlikely to meet its climate goals if it doesn’t reduce vehicle travel. So far, however, state and local efforts to reduce vehicle miles traveled (VMT) have fallen short of expectations, even as cities grow more compact and public transit funding has increased. To better understand the role of highway expansion in meeting California’s climate goals, this study analyzed whether a simple model that only considers road capacity and population growth can predict VMT as well as traditional transportation models. It also looked at the share of recent VMT growth that has been caused by expanded road capacity, and the reductions in VMT from transit and other projects funded by California’s climate investments.

research report

Changes in Activity-Travel Patterns and Vehicle Ownership During the COVID-19 Pandemic in California

Publication Date

October 1, 2024

Author(s)

Giovanni Circella, Xiatian Iogansen, Grant Matson, Keita Makino, Yongsung Lee

Areas of Expertise

Travel Behavior, Land Use, & the Built Environment

Abstract

This report summarizes the findings from ten sets of analyses that investigated ways the COVID-19 pandemic transformed people’s activity-travel patterns. Data were collected through three waves of surveys in Spring 2020, Fall 2020, and Summer 2021 in California and the rest of the US. There was a substantial shift among California workers from physical commuting to exclusive remote work in 2020, followed by a transition to hybrid working schedules by Summer 2021. The adoption of remote work and hybrid work varied significantly among population subgroups, with higher income, more educated individuals, and urban residents showing the greatest shift to these arrangements. In terms of mode use and vehicle ownership, increased concerns about the use of shared modes of travel correlated with an increasing desire to own a car. There was a major decrease in walking for commuting purposes observed and a significant increase in walking and biking for non-work trips. The study also found a reduction in the demand for, and/or an elevated aversion to, ridehailing because of the shared nature of the service. Regarding shopping patterns, the study found a nearly five-fold increase in the number of respondents who shopped online at least once per week between Fall 2019 and Spring 2020. However, part of this increase vanished by Fall 2020. Overall, the pandemic brought both temporary changes and longer-term impacts. The study proposes strategies to promote sustainable transportation and social equity among different population groups as communities strive to recover from the pandemic.

published journal article

Impact of Debris Removal Post-Wildfires on Pavement Fatigue and Rutting Lives: Case Studies of California’s Camp and Carr Fires

Publication Date

October 1, 2024

Author(s)

Ali Zarei, Changmo Kim, Ali A. Butt, Rongzong Wu, Jeremy Lea, Somayeh Nassiri

Areas of Expertise

Infrastructure Delivery, Operations, & Resilience

Abstract

Between 2017 and 2018, California experienced a series of four devastating fires, including the Camp and Carr Fires, which ranked among the most destructive fires in U.S. history. During these fires, roads were critical in the evacuation, rescue operations, goods transportation, and access to critical services. Additionally, postfire, road infrastructure became crucial for removing hazardous and nonhazardous waste from fire-affected areas to major landfills and recycling facilities. Despite the significance of pavements in this process, previous studies have not quantitatively assessed the potential damage caused to pavements by the additional trucks used in debris removal operations. This research aimed to address this knowledge gap by collecting precise traffic data for the routes taken to waste management facilities, including data on the number of trips involved in debris transportation. The traffic information was then utilized to calculate changes in equivalent single axle loads and traffic index values for pavement design. Pavement structures were obtained from the available core database. Pavement simulation results showed that of the nine studied highways, only one exhibited a reduction in cracking life of about 2 years. However, Skyway, the main artery in the town of Paradise, demonstrated a significantly accelerated fatigue cracking failure by 14.3 years. A sensitivity analysis of fire intensity showed other highway sections that were structurally adequate could be affected by larger fires. The presented methodology could be used in traffic planning as part of debris management operations to avoid vulnerable pavement sections.

policy brief

How Cooperation Between Connected Automated Vehicles and Smart Infrastructure Can Improve Situational Awareness for Traffic Safety

Publication Date

February 1, 2025

Author(s)

Xin Xia, Jiaqi Ma, Zhaoliang Zheng, Yunpeng Luo, Fayzah Alshammari, Letian Gao, Hao Xiang, Alfred Chen

Areas of Expertise

Infrastructure Delivery, Operations, & Resilience Intelligent Transportation Systems, Emerging Technologies, & Big Data

Abstract

Escalating trends in pedestrian and cyclist fatalities points to a pressing need to improve traffic safety, especially for vulnerable road users such as pedestrians, cyclists, and scooters. A key challenge in enhancing intersection safety is the lack of accurate, detailed, and real-time data that captures the complexities of these dynamic and uncertain environment. If intersections themselves could “see” the diverse array of vehicles, pedestrians, cyclists, and scooters, each with unique movement patterns and safety needs, this could vastly improve safety. Making intersections “smart” by equipping them with Light Detection and Ranging (LiDAR) technology that can capture a detailed and real-time 3D environment could facilitate the accurate detection of vehicles and other road users, to better control signal timing and assist future connected vehicles (CVs) and/or connected automated vehicles (CAVs) in driving safely.

research report

Benefits, Challenges, and Opportunities of Different Last-Mile Delivery Strategies

Areas of Expertise

Freight, Logistics, & Supply Chain

Abstract

As online shopping nears its third decade, it is clear that its impacts on urban goods flow are profound. Increased freight traffic and related negative externalities such as greenhouse gas emissions and local air pollution can impede sustainability goals. In response, e-retailers are exploring innovative distribution strategies to enhance last-mile delivery sustainability and efficiency. They use urban consolidation centers with light-duty vehicles like electric vans and cargo bikes, establish alternative customer pickup points, and deploy crowdsourced delivery networks. Advanced technologies that may streamline deliveries, such as autonomous delivery robots and unmanned aerial vehicles, are being tested. University of California Davis and Irvine researchers have investigated these strategies under economic viability, environmental efficiency, and social equity frameworks. Different modeling approaches were implemented to evaluate last-mile network designs and the potential for decarbonizing delivery fleets by switching to electric vehicles. Key findings suggest that while these innovative strategies offer substantial environmental benefits and reduce operational costs, they also present challenges like higher initial investments and operational hurdles. The study emphasizes the need for ongoing innovation and careful strategy implementation to balance sustainability with urban delivery systems’ economic and service reliability demands.

published journal article

Real-World Activity Patterns of Heavy-Duty Battery Electric Trucks from Regional Distribution Fleets in Southern California

Publication Date

January 6, 2024

Author(s)

Kanok Boriboonsomsin, Alexander Vu

Areas of Expertise

Freight, Logistics, & Supply Chain Zero-Emission Vehicles & Low-Carbon Fuels

Abstract

Heavy-duty trucks are a major source of transportation-related greenhouse gas and criteria pollutant emissions. One approach to reducing these trucks’ climate and health impacts is to transition them to zero-emission technologies such as battery electric trucks (BETs). To date, BETs have been deployed mostly in drayage applications. As the performance of BETs has improved in recent years, there is increasing interest in using BETs also in regional haul applications. This paper examines real-world activity patterns of 15 heavy-duty BETs in regional haul applications using data collected from early deployments of these trucks across eight different fleets in Southern California. The results show that the BETs are typically utilized on routes (or tours) that are much shorter than their driving ranges. They often make one or two tours per day and are usually charged at the end of each tour. Due to the variation in the time of day that the BETs are operated, they are charged at different times of day, spreading the charging load throughout the day. In addition, the results indicate that about half of the BET’s operations on average occur in or around disadvantaged communities, providing emission reduction benefits to these communities.

published journal article

Quantifying the Employment Accessibility Benefits of Shared Automated Vehicle Mobility Services: Consumer Welfare Approach Using Logsums

Publication Date

October 5, 2020

Author(s)

Tanjeeb Ahmed, Michael Hyland, Navjyoth Sarma , Arash Ghaffar

Areas of Expertise

Intelligent Transportation Systems, Emerging Technologies, & Big Data Safety, Public Health, & Mobility Justice

Abstract

The goal of this study is to assess and quantify the potential employment accessibility benefits of shared-use automated vehicle (AV) mobility service (SAMS) modes across a large diverse metropolitan region considering heterogeneity in the working population. To meet this goal, this study proposes employing a welfare-based (i.e. logsum-based) measure of accessibility, obtained via estimating a hierarchical work destination-commute mode choice model. The employment accessibility logsum measure incorporates the spatial distribution of worker residences and employment opportunities, the attributes of the available commute modes, and the characteristics of individual workers. The study further captures heterogeneity of workers using a latent class analysis (LCA) approach to account for different worker clusters valuing different types of employment opportunities differently, in which the socio-demographic characteristics of workers are the LCA model inputs. The accessibility analysis results in Southern California indicate: (i) the accessibility benefit differences across latent classes are modest but young workers and low-income workers do see higher benefits than high- and middle-income workers; (ii) there are substantial spatial differences in accessibility benefits with workers living in lower density areas benefiting more than workers living in high-density areas; (iii) nearly all the accessibility benefits come from the SAMS-only mode as opposed to the SAMS+Transit mode; and (iv) the SAMS cost per mile assumption significantly impacts the magnitude of the overall employment accessibility benefits.