UC Davis Institute of Transportation Studies

We interviewed eight subject-matter experts in California in 2023 tounderstand how travel behavior and priorities may change in response to direct experience with road collisions. Expertsrepresented a variety of perspectives, including medical doctors, advocates for active transportation safety, and advocates for people with disabilities. Their diverse specialties enabled us to capture a variety of concerns without triggering emotionally sensitive areas for people who have directly experienced road collisions. These experts identified common themes, including mental stress from the prospect of returning to driving—especially on freeways, lesser incidence of long-term changes in travel modes after experiencing a collision, dependence on others for rides in private vehicles, and changing routes or times of day of travel when traveling independently. These experts also explained how people’s mode choices are also affected by general concerns about collisions in the news more than by specific personal experiences with near misses. Interview subjects’ spoke of more specific concerns as well. These included but were not limited to, bicyclists using sidewalks instead of bike lanes when both are present, feeling stigmatized from using public transit or paratransit after experiencing a collision, and concerns with motorists treating bicyclists badly. These initial interviewsclarify areas of focus and methodology for future qualitative and quantitative studies on the intersection oftransportation safety and travel behavior change, particularly as they involve people who have directly experienced road collisions.

This study discusses the potential economic and development impacts that high-speed rail (HSR) may bring to California. The research reviews the reported impacts of HSR implementation in various countries, particularly in Europe, and case studies of selected HSR station-cities in France, Spain, and Italy. The analysis suggests that HSR could bring economic development to the state and stimulate population growth but might eventually lead to gentrification in certainlocations. Not all station-cities experience the same impacts, and certain conditions may foster greater economic development. Station location and connectivity to downtown areas would be particularly important in influencing these impacts, while peripheral stations would be less able to attract land use development and relocation of activities. The availability of rail service to larger cities (and connections to other major markets) and the coordination with urban planning and policy are key to determining the development of areas around HSR stations. The study indicates that for HSR to bring about desired economic development, the planning and design of stations and services must be integrated with the vision and urban plans of each station-city.

The primary metric for measuring electric vehicle (EV) adoption growth is new car sales. However, to enable mass market penetration, EV adoption in the used car market will play a crucial role. The used vehicle market is relatively under-studied or has been studied mostly for specific regions. This project analyzed US national consumer expenditure survey data that tracks households' expenditure on vehicle acquisition and operation. The study aim is to understand new versus used vehicle choice behavior and the consequent cost of vehicle ownership, with the larger aim of determining how much households who generally buy used vehicles can gain or lose if they transition from a used internal combustion engine vehicle (ICEV) to a used EV. A choice model and cluster analysis showed that ownership of used vehicles is influenced by family size, income, housing tenure, and age. For lower-income renters, current vehicle ownership and purchase costs tend to constitute a high fraction of their household income, raising concerns related to equity and suggesting that these households in particular should be considered in policies to encourage the EV transition. Moreover, while at present the average price paid for a used ICEV is approximately $18,000, the price of a comparable used EV can range between $14,000 (e.g., lower electric range Nissan Leaf) to $50,000 (high-range Tesla), suggesting the need for incentives to encourage the used EV market.

A lack of reliable and affordable transportation exacerbates socioeconomic inequities for low-income individuals, especially people of color. Universal Basic Mobility (UBM) pilots or programs are a relatively new approach to addressing financial barriers to travel among the transport-disadvantaged. UBMs provide individuals with funds for various mobilityoptions, including transit and shared modes. This study reviews the UBM programs and pilots implemented in the United States. It also reviews international applications of Mobility as a Service (MaaS) platforms. These platforms may reduce the administrative cost of implementing UBMs and help users identify and compare available travel options. In addition, the review describes critical program design tradeoffs to consider when developing a UBM program or pilot. Finally, key UBM elements and lessons learned are summarized to assist other communities considering UBMs.

Lithium-ion batteries (LIBs) are the enabling technology for modern electric vehicles (EVs), allowing them to reach driving ranges and costs comparable to internal combustion engine vehicles, an important development with EVs being integral to greenhouse gas mitigation efforts. However, LIB advancements include the use of rapidly evolving and chemically diverse batteries as well as larger battery packs, raising concerns about battery production sustainability as well as battery end-of-life (EoL). This study seeks to respond to these concerns by analyzing potential pathways for EoL EV batteries, quantifies flows of retiring EV battery materials, proposes economically and environmentally preferable LIB EoL strategies, and recommends pertinent policies with an emphasis on environmental justice. The researchers used a loosely coupled dynamic systems model that utilized life cycle assessment and material flow analysis and a mixed methods research approach. They find that the U.S. can make significant gains in securing supply chains for critical materials and decrease life cycle environmental impacts through the adoption of Recycled Content Standard policies similar to those found in the European Union. In addition, they examine the currently understood waste hierarchy in the context of LIB technology. Comparing immediate recycling to repurposing and reusing, they find that repurposing and reusing reduces life cycle environmental impacts relative to recycling. This project also includes an investigation of EoL battery collection and transportation and the vehicle afterlife ecosystem, as well as general stakeholders in the LiB life cycle, informed by expert interviews and a case study of a developing lithium industry in Imperial, California.

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Pooled trips in private vehicles, or pooling, can lead to smaller environmental impacts and more efficient use of the limited roadway capacity, especially during peak hours. However, pooling has not been well adopted in part because of difficulties in coordinating schedules among various travelers and the lack of flexibility to changes in schedules and locations. In the meantime, ridehailing (RH) provides pooled services at a discounted fare (compared to the single-travel-party option) via advanced information and communication technology. This study examines individuals’ preferences for/against pooled RH services using information collected among travelers answering a set of questions related to their last RH trip. In doing so, both trip attributes and rider characteristics are considered. Taste heterogeneity is modeled in a way that assumes the presence of unobserved groups (i.e., latent classes), each with unique preferences, in a given sample of RH riders (N=1,190) recruited in four metropolitan regions in Southern U.S. cities from June 2019 to March 2020. The researchers find two latent classes with qualitatively different preferences, choosy poolers and non-selective poolers, regarding their choice in favor of/against pooling based on wait time, travel costs, purpose, and travel party size of the last RH trip. Personal characteristics are also identified, specifically age and three attitudes (travel satisfaction, environmentalism, and travel multitasking), which account for individuals’ class membership. This research contributes to the literature by explicitly modeling taste heterogeneity towards pooled ridehailing. In addition, unlike existing studies either at the person level or employing stated-preference data, a trip-level analysis is performed in connection with revealed preferences, which generates more realistic and relevant implications to policy and practice.

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Vehicle electrification has attracted strong policy support in California due to its air quality and climate benefits from adoption. However, it is unclear whether these benefits are equitable across the state’s sensitive populations and socioeconomic groups and whether disadvantaged communities are able to take advantage of the emission savings and associated health benefits of electric vehicle (EV) adoption. In this study, we analyze the statewide health impacts from the reduction of on-road emissions reduction (from reducing gasoline powered cars) and the increase in power plant emissions (from EV charging) across disadvantaged communities (DACs) detected by using the environmental justice screening tool CalEnviroScreen. The results indicate that EV adoption will reduce statewide primary PM2.5 emissions by 24.02-25.05 kilotonnes and CO2 emissions by 1,223-1,255 megatonnes through 2045, and the overall monetized emission-related health benefits from decreased mortality and morbidity can be 2.52-2.76 billion dollars overall. However, the average per capita per year air pollution benefit in DACs is about $1.60 lower than that in the least 10% vulnerable communities in 2020, and this disparity expands to over $31 per capita per year in 2045, indicating that the benefits overlook some of the state's most vulnerable population, and suggesting clear distributive and equity impacts of existing EV support policies. This study contributes to our growing understanding of environmental justice rising from vehicle electrification, underscoring the need for policy frameworks that create a more equitable transportation system.

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Between 2017 and 2018, California experienced four devastating fires, including the Camp and Carr Fires. After fires, road infrastructure is crucial for safe removal of hazardous materials and waste to landfills and recycling facilities. Despite the critical role of pavements in this process, there has been little quantitative evaluation of the potential damage to pavements from truck traffic for debris removal. To address this knowledge gap, data on truck trip numbers and debris tonnage following the Camp and Carr Fires were used to calculate changes in equivalent single axle loads and traffic index over the pavement’s design life (the age at which reconstruction would be considered). Simulations were conducted on existing pavement structures to assess potential additional damage based on increased traffic indices. Pavement structural design simulations showed that out of the nine studied highways, one exhibited a reduction in cracking life of about two years from debris removal operations. However, fatigue cracking was significantly accelerated for Skyway, the major road in the Town of Paradise, failing 14.3 years before its design life. A methodology similar to the one presented in this study can be adopted in debris management planning to strategically avoid vulnerable pavements and minimize damage to the highway network.

The Low Carbon Fuel Standard (LCFS) plays a critical role in California’s efforts to reduce greenhouse gas (GHG) and air pollutant emissions from transportation. The LCFS incentivizes the use of fuels with lower life cycle GHG emissions by using a credit market mechanism to provide incentives for low-carbon fuels, using revenue generated by charges applied to high-carbon ones. Maintaining an approximate balance between LCFS credit and deficit supplies helps support a stable LCFS credit price and the broader transition to low-carbon transportation. The Fuel Portfolio Scenario Model, presented here, evaluates bottom-up fuel supply and LCFS compliance to inform LCFS policy decisions. We considered two key fuel demand scenarios: (1) the Low Carbon Transportation scenario, reflecting the expected transition to low-carbon transportation in California over the next 15 years, and (2) the Driving to Zero scenario, featuring a significantly higher consumption of petroleum gasoline. In both scenarios, 2030 LCFS targets around 30% resulted in a near-balance between credits and deficits, with some banked credits remaining. Several additional scenarios were modeled to explore the impact of target trajectory timing, alternate post-2030 targets, greater biofuel use, and other parameters. This fuel portfolio scenario modeling work can meaningfully inform policy development.