policy brief

What are the Equity Implications of Robo-taxis in terms of Job Accessibility Benefits?

Abstract

After years of research and development, companies are now operating fully driverless shared-use automated vehicle-enabled mobility services (SAMS) or “robo-taxis“ in Arizona and California. SAMS offer several potential benefits to travelers and society including reducing vehicle ownership, parking demand, congestion, crashes, energy consumption, and emissions, as well as increasing roadway capacity, mobility, and accessibility. Moreover, previous research by our team found that SAMS can provide significant job accessibility benefits to workers in California. To better understand the equity implications of the job accessibility benefits from SAMS, we analyzed the distribution of SAMS benefits across different segments of the population (e.g., low- vs. high-income, young vs. old).
To measure the accessibility benefits of SAMS, we use the logsum of a hierarchical work destination and commute mode choice model—a monetary measure of consumer surplus consistent with microeconomic and utility maximization theories. If a new commute mode (e.g., SAMS) is made available to travelers, and that new mode is competitive with existing modes in terms of travel time and travel cost, then the new mode will improve a traveler’s job accessibility. For more information, please see our previous study on measuring the job access benefits of SAMS2.

published journal article

Telecommuting and Travel during COVID-19: An Exploratory Analysis across Different Population Geographies in the U.S.A.

Abstract

This study explores the impact of the COVID-19 pandemic on telecommuting (working from home) and travel during the first year of the pandemic in the U.S.A. (from March 2020 to March 2021), with a particular focus on examining the variation in impact across different U.S. geographies. We divided 50 U.S. states into several clusters based on their geographic and telecommuting characteristics. Using K-means clustering, we identified four clusters comprising 6 small urban states, 8 large urban states, 18 urban-rural mixed states, and 17 rural states. Combining data from multiple sources, we observed that nearly one-third of the U.S. workforce worked from home during the pandemic, which was six times higher than in the pre-pandemic period, and that these fractions varied across the clusters. More people worked from home in urban states compared with rural states. As well as telecommuting, we examined several activity travel trends across these clusters: reduction in the number of activity visits; changes in the number of trips and vehicle miles traveled; and mode usage. Our analysis showed there was a greater reduction in the number of workplace and nonworkplace visits in urban states compared with rural states. The number of trips in all distance categories decreased except for long-distance trips, which increased during the summer and fall of 2020. The changes in overall mode usage frequency were similar across urban and rural states with a large drop in ride-hailing and transit use. This comprehensive study can provide a better understanding of the regional variation in the impact of the pandemic on telecommuting and travel, which can facilitate informed decision-making.

research report

Investigation of LiDAR Sensing Technology to Improve Freeway Traffic Monitoring

published journal article

Health and equity impacts from electrifying drayage trucks

Abstract

Diesel heavy-duty drayage trucks (HDDTs) serving the Ports of Los Angeles and Long Beach in Southern California are large contributors to regional air pollution, but cost remains an obstacle to replacing them with zero-emission HDDTs. To quantify the health and equity impacts of operating diesel HDDTs, we built a microscopic simulation model of a regional freeway network and quantified their emissions of PM2.5 (particulate matter with a diameter < 2.5 μm) and CO2 in 2012 and 2035, before estimating their contribution to selected health outcomes. We found that 483 premature deaths ($5.59 billion) and 15,468 asthma attacks could be attributed to HDDTs in 2012. Regulations and technological advances could shrink these impacts to 106 premature deaths ($1.31 billion) and 2,142 asthma attacks in 2035 (over 2/3 accruing to disadvantaged communities) despite population growth and a 145 % jump in drayage traffic, but they still justify replacing diesel HDDTs with zero-emission HDDTs by 2035.

journal article preprint

Impacts of the COVID-19 Pandemic on Telecommuting and Travel

Abstract

This chapter examines changes in telecommuting and the resulting activity-travel behavior during the COVID-19 pandemic, with a particular focus on California. A geographical approach was taken to “zoom in” to the county level and to major regions in California and to “zoom out” to comparable states (New York, Texas, Florida). Nearly one-third of the domestic workforce worked from home during the pandemic, a rate almost six times higher than the pre-pandemic level. At least one member from 35 percent of U.S. households replaced in-person work with telework; these individuals tended to belong to higher-income, White, and Asian households. Workplace visits have continued to remain below pre-pandemic levels, but visits to non-work locations initially declined but gradually increased over the first nine months of the pandemic. During this period, the total number of trips in all distance categories except long-distance travel decreased considerably. Among the selected states, California experienced a higher reduction in both work and non-workplace visits, and the State’s urban counties had higher reductions in workplace visits than rural counties. The findings of this study provide insights to improve our understanding of the impact of telecommuting on travel behavior during the pandemic

Phd Dissertation

Alternative Fuel Adoption Behavior of Heavy-duty Vehicle Fleets

Abstract

Alternative fuel adoption by heavy-duty vehicle (HDV) fleets can bring substantial benefits to both current local communities and future generations by reducing air pollutants and greenhouse gas emissions. However, the penetration rate of alternative fuel vehicles (AFVs) is still very low in the HDV sector. Revealing HDV fleet operator perspectives towards alternative fuels can serve as the basis for developing effective policies for accelerating the diffusion of these technologies. This dissertation aims to fill a key knowledge gap, where such fleet operator perspectives have rarely been addressed, by exploring alternative fuel adoption behavior of HDV fleets.An initial theoretical framework was first developed based upon existing theories and literature to conceptually understand AFV fleet adoption behavior in organizations. This initial framework consists of a five-stage adoption process as well as two levels of sub-frameworks: at the decision-making unit level and the individual (e.g., vehicle drivers) acceptance level. Next, it was attempted to empirically improve the initial framework by investigating 20 organizations operating HDVs in the State of California via in-depth qualitative interviews and project reports. A total of 29 adoption and 42 non-adoption cases was probed across various alternative fuel technologies, including natural gas, propane, electricity, hydrogen, biodiesel, and renewable diesel options. The qualitative data was analyzed using content and thematic analyses, by which numerous themes and hypotheses were developed to build a theory explaining heavy-duty AFV fleet adoption behavior. Based on these qualitative inferences, a conceptual modelling framework was proposed for estimating demand for heavy-duty AFVs under different policy and technology advancement scenarios. An overall structure along with specific modules and components for this framework are presented. As an ongoing work, a stated preference choice experiment was designed to quantitatively operationalize one of the modules, to estimate AFV choice probabilities. The feasibility of this modelling approach is proposed to be examined in a case study interviewing California drayage fleet operators. Finally, the research findings contribute theoretically and empirically to a better understanding of the demand-side aspects of AFV adoption by HDV fleet operators, particularly in California and in the other US states that follow California’s environmental policies.

book/book chapter

Understanding and Modeling the Impacts of COVID-19 on Freight Trucking Activity

Abstract

Restrictions on travel and in-person commercial activities in many countries (e.g., the United States, China, European countries, etc.) due to the global outbreak and rapid spread of the coronavirus disease 2019 (COVID-19) have severely impacted the global supply chain and subsequently affected freight transportation and logistics. This chapter summarizes the findings from the analysis of truck axle and weight data from existing highway detector infrastructure to investigate the impacts of COVID-19 on freight trucking activity. Three aspects of COVID-19 truck impacts were explored: drayage, long and short-haul movements, and payload characteristics. This analysis revealed disparate impacts of this pandemic on freight trucking activity because of local and foreign policies, supply chain bottlenecks, and dynamic changes in consumer behavior. Due to the ongoing effects of COVID-19, it is not yet possible to distinguish between transient and long-term impacts on freight trucking activity. Nonetheless, a future expansion of the study area and the incorporation of other complementary data sources may provide further insights into the pandemic’s impacts on freight movement.

published journal article

Grocery shopping in California and COVID-19: Transportation, environmental justice, and policy implications

Abstract

To understand how COVID-19 changed grocery shopping and explore implications for transportation and environmental justice, we surveyed in May 2021 California members of KnowledgePanel®, the largest and oldest U.S. probability-based panel. We asked how frequently Californians grocery shopped before and during the pandemic, and how they may grocery shop afterward in-store, online with home delivery (“e-grocery”), or online with store/curbside pick-up (“click-and-pick”). We found that most Californians continued to grocery shop in-person during the pandemic, although less frequently than before. Many relied more on e-grocery (+8.9 %) and click-and-pick (+13.3 %), although older generations remained attached to in-store shopping. African American households grocery shopped in-store less than Whites pre-pandemic; post-pandemic, they may compensate with more e-grocery and click-and-pick. While higher levels of environmental injustice (based on CalEnviroScreen) were associated with less in-store shopping, we found no association with e-grocery or click-and-pick. Our results have implications for travel, food logistics, and parking management.

Phd Dissertation

Resilient spatiotemporal truck monitoring framework using inductive signature and 3d point cloud-based technologies

Abstract

Understanding the spatiotemporal distribution of commercial vehicles is essential for facilitating strategic pavement design, freight planning, and policy making. Hence, analysts and researchers have been increasingly interested in collecting more diverse high granularity truck data across different truck characterization schemes to meet these various needs across the roadway network to better understand their distinct operational characteristics and dissimilar impacts on infrastructure and the environment. Existing truck monitoring infrastructure is limited in spatial coverage across the roadway network due to high installation and maintenance costs. The recently developed Truck Activity Monitoring System (TAMS) by the University of California Irvine Institute of Transportation Studies provides a cost-effective solution for monitoring truck movements statewide across California along major freeways networks through existing inductive loop infrastructure enhanced with inductive signature technology. Nonetheless, it possesses three major limitations: model bias against underrepresented truck classes, spatial coverage limitation on rural highways, and system obsolescence over time. This dissertation explored a resilient spatiotemporal truck monitoring system using inductive loop signature and multi-array Light Detection and Ranging (LiDAR) sensor technologies to address the aforementioned issues and to improve truck monitoring capabilities across the roadway network. The designed system comprises three major parts: Inductive loop sensors for major highway truck monitoring, multi-array LiDAR sensors for rural highway truck monitoring, and a self-learning truck classification framework through a sensor integration framework. The first part of the system was built upon the existing Truck Activity Monitoring System (TAMS) developed by ITS Irvine and addresses prediction model biasness caused by inherently imbalanced truck datasets to provide reliable truck speed estimation and truck classification data. The second part explored non-intrusive LiDAR-based sensing technologies to fill the surveillance gap along rural highway corridors. This section developed a truck classification method using a LiDAR sensor oriented to provide a wide field-of-view of roadways. Finally, a self-learning framework for truck classification systems was designed to address system obsolescence through the integration of inductive loop sensors and LiDAR sensors, the latter of which has been proven in this dissertation to have the ability to recognize truck axle configuration. This framework enhances the resilience of the signature-based FHWA classification model with an intelligent system update to accommodate the change of the truck designations over time and significantly reduces the overall burden of periodic model calibration by utilizing the information stored in the legacy model. 

published journal article

Equity Implications of Robo-Taxis on Job Accessibility: Avoiding the Ecological Fallacy with Agent-Based Models

Abstract

Robo-taxis or shared-use automated vehicle-enabled mobility-on-demand services (SAMSs) are now in operation in the US and China. By removing drivers’ labor costs, SAMSs promise to provide significantly lower-cost transportation than human-driven mobility-on-demand services. Under this assumption, prior research indicates SAMS can provide sizable employment accessibility benefits to workers. The current paper aims to analyze the distribution of SAMS accessibility benefits across segments of the population (i.e., perform an equity analysis) using an agent-based travel modeling approach. The study’s methodology (i) clusters workers by their socio-demographic and -economic characteristics using latent class analysis, (ii) estimates hierarchical work location and commute mode choice models for four worker segments, and (iii) obtains logsum-based monetary measures of accessibility for each worker in a synthetic population of Southern California. Using this information, we analyze the distributions of SAMS accessibility benefits across several population segmentations. We utilize box plots to visualize the distributional differences across population segments. Additionally, we use ANOVA and post-hoc Tukey’s Honestly Significant Difference tests to analyze the overall and inter-group statistical significance of the distributional differences, respectively. The results indicate that low-income, Black, and Hispanic workers receive larger SAMS accessibility benefits on average than high-income, White, and Asian workers. Additionally, workers in zero-car households benefit more from SAMSs than one- and multi-car households, particularly after conditioning on the transit accessibility of the worker’s residence. The study also aggregates the agents into their origin census tracts, classifies the census tracts based on agent socio-demographic attributes, and then analyzes the distribution of SAMS accessibility benefits across census tract designations (e.g., low median income tracts vs. high median income tracts). The study finds that if analysts were to make individual-level inferences based on the spatial analysis, the inferences would be inaccurate in the case of household income and age, thereby misinforming policymakers regarding who benefits more/less from SAMS.