UC Davis Institute of Transportation Studies

Higher-occupancy self-driving shuttles could bring about the benefits of vehicle automation—improved safety, parking cost savings, greater mobility to those who cannot drive, and stress relief for drivers. At the same time, these shuttles would not bring the potential drawbacks of self-driving vehicle ownership, such as increases in vehicle miles traveled and associated energy use. Because they can only currently operate in relatively simple and closed environments, self-driving shuttles are likely to be deployed earlier than personal self-driving vehicles in open road environments. However, acceptance of the new technology remains uncertain. Whether people will use these services will be largely influenced by their attitudes toward self-driving technology.

Researchers at the University of California, Davis surveyed residents and employees of the West Village area of the UC Davis campus during the three-month pilot deployment of a self-driving, electric shuttle to understand attitudes toward self-driving technology. The researchers then applied existing theories of technology adoption to model how attitudes of residents and employees influenced their acceptance of the shuttle service. This policy brief summarizes findings from that research and provides policy implications of self-driving shuttles.

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Recent research suggests that bird populations are declining at alarming rates across the United States. Over the last century, local, national, and international efforts to limit declines in bird populations have resulted in state and federal laws that now protect most of California’s 650 bird species. To comply with these protections, transportation infrastructure projects often face strict mitigation requirements, which can be expensive and cause delays. Understanding a project’s effects on specific bird populations can refine mitigation requirements and optimize infrastructure planning.

The tools for identifying separate populations within species and understanding protected birds’ seasonal movement have been limited until recently. New genetic and genomic tools now provide a method for understanding population differentiation, which is vital to a wide array of conservation goals including estimating population declines, identifying potential for adaptation to stressors, measuring connectivity between populations, and estimating inbreeding. Because infrastructure projects can directly impact genetic diversity and connectivity, a toolkit to assess population structure and the distribution of genetic variation could aid in predicting and mitigating the impacts of such projects. As a test case, researchers at the University of California, Davis, sequenced entire genomes for 40 individual Anna’s hummingbirds (Calypte anna) from across California to identify breeding populations and develop a genetic toolkit to assign individuals to those populations. The presence of this species at bridge construction sites has resulted in construction delays in part because little information exists on the status of different populations within the species.

This research brief summarizes findings and implications from the project.

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California has goals to rapidly expand electric vehicle adoption, with executive orders calling for 1.5 million electric vehicles on the roads by 2025 and 5 million by 2030. Significant charging infrastructure will be needed to support these new vehicles. While many urban areas in California have prioritized construction of charging stations, most rural areas lack charging infrastructure. This deficit hinders electric vehicle adoption in rural areas and makes long distance electric vehicle travel difficult.

To address this issue, Caltrans has begun investing in charging infrastructure in rural and underserved areas around the state, particularly at highway rest areas. However, an understanding of potential future intercity charging demand will be needed to inform continued investments in support of a growing electric vehicle fleet.

This policy brief summarizes findings from researchers at the University of California, Davis, who collected state travel data and electricity demand data to run a model that identified optimal highway rest areas for electric vehicle charger installation and calculated how an increase in charging demand would affect the California electricity grid at selected highway locations. The project aimed to maximize the use and generation of solar and wind energy, while also increasing electric vehicle adoption and mobility in the state.

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As roads and other developed land uses proliferate, the resulting habitat fragmentation and loss of wildlife connectivity hinder animals’ ability to forage, establish new territories, and maintain genetic diversity. Wildlife crossing structures such as culverts and bridges theoretically can reduce these impacts by allowing species to effectively cross highways. However, previous research has shown that traffic presence and density can disrupt wildlife use of highway crossing structures, and that noise and light from human activities can affect animal behavior. Researchers at the University of California, Davis, Road Ecology Center measured traffic noise and light levels and placed motion- and heat-triggered cameras at 26 bridges and culverts along four interstate highways, 11 state highways and one major county road across California. The presence and behavior of animals at these highway crossing structures were compared to those detected at sites unaffected by roads to understand the effects of noise and light from a highway on wildlife behavior. This policy brief summarizes findings from that research and provides policy implications.

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One of the potential consumer benefits of electric vehicles (EVs) is lower fuel and maintenance costs compared to internal combustion engine vehicles (ICEVs). Consumers tend to have difficulty recognizing these cost benefits, however, because of the complexity of comparing gasoline and electricity prices, and comparing long-term operating savings with EV purchase premiums. Online vehicle cost calculators may help consumers navigate this complexity by providing tailored cost estimates and enabling comparisons across vehicles. Of the several vehicle cost calculators available online, functionalities range widely. No existing research establishes the functionalities and features that determine the usefulness of vehicle cost calculators in promoting EV adoption. Researchers at the University of California, Davis drew upon a systematic review of vehicle cost calculators and findings from multiple user experience studies to articulate best practices for the user interface design of effective vehicle cost calculators. The researchers categorized best practices as those related to the vehicle cost calculator use cases, outputs, user experience, and user inputs.

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Bike-share services have rapidly expanded in cities worldwide and attracted substantial ridership, especially as electric and dockless bike- and scooter-share services have entered the market. These services have the potential to offer a healthier and more environmentally sustainable mobility option if used as an alternative to car travel and a connection to transit. However, little is known about the influence of bike-share systems on individual travel behavior; particularly if bike-share trips are replacing vehicle trips and increasing transit use. To address this knowledge gap, researchers at the University of California, Davis surveyed Sacramento-area residents before and after the 2018 implementation of a JUMP/Uberoperated dockless electric bike-share program to examine how the micromobility service influenced general travel behavior and attitudes. Surveys were sent to residents in downtown Sacramento, West Sacramento, and Davis within the bike-share service area and to a control group in Sacramento outside the service area. Key findings from the research are summarized in this brief.

This study aims to provide an overview of the different technologies of electrification, automation and shared mobility (3Rs) in freight transportation for the long-haul and last mile. The study provides a view of their penetration status and explores the potential, challenges, and unintended consequences of their arrival in the transportation system. An overview is also provided of the required changes and the driving forces needed to foster the 3Rs in freight. The results can help inform the development of the next phases and future steps, plans, and policies or initiatives needed for the next generation of the freight transportation system, especially in urban areas. This research brief summarizes those findings.

Prior to the last decade, the logistics industry trended towards the development of mega-warehouse facilities in suburban settings far from core markets, creating a phenomenon known as logistics sprawl. This trend is particularly prominent in Southern California (Figure 1). Since the 2008-2009 economic crisis, however, the trend has shifted. The rise of e-commerce may have influenced supply chain decisions to locate warehouses and distribution centers closer to denser urban areas to enable faster deliveries to consumers. The changes in size and spatial distribution of warehouses and distribution centers as well as the environmental and equity implications of these changes are not fully understood. As warehouses and distribution centers locate in denser urban areas, they may introduce additional diesel truck traffic into disadvantaged and low-income communities.

To gain a better understanding of how the spatial distribution and size of freight facilities are changing and the implications of these changes for disadvantaged and low-income communities, researchers at the University of California, Davis analyzed aggregate data about the number of warehouses and distribution centers and disaggregate real estate data of purchases and leases during the last three decades in California. They also analyzed the relationship between freight facilities and communities of concern using the California Environmental Protection Agency’s CalEnviroScreen 3.0 tool. The research focused on the San Diego, Los Angeles, San Francisco, San Joaquin Valley, and Sacramento regions. Key findings from the research are presented in this brief.

More than 90 percent of the road and highway network in the United States is paved with asphalt concrete. Maintenance and periodic rehabilitation require a continuous supply of aggregates and asphalt binder, both of which are becoming increasingly scarce and expensive. Recycling and reusing these resources can reduce costs and improve sustainability. The most common recyclable material used in road construction is reclaimed asphalt pavement (RAP), which is milled asphalt surface layers that have been removed from existing pavements before new asphalt overlay is placed. Reclaimed asphalt roofing shingles (RAS) are another potential source of asphalt binder.

There is growing interest in allowing significantly higher percentages of RAP and RAS in asphalt mixes used on state and local roadways. However, making this change has raised concerns regarding how these composite binders may influence the performance and durability of asphalt mixes, depending on the blends of different virgin and reused binders. Researchers at the UC Pavement Research Center investigated the use of higher percentages of RAP and RAS as a partial replacement for the virgin binder in new asphalt mixes and their effect on pavement performance in California. This research brief summarizes findings from that study.

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Consumers are purchasing and using partially automated vehicles, yet little research has been conducted to understand how and if these vehicles are changing travel behavior. Fully automated, or driverless, vehicles are receiving much more research and policy attention but are still many years from market introduction. Research on fully automated vehicles has shown that, without proper policies in place, these vehicles could increase vehicle miles travelled (VMT). Tesla vehicle models with the ‘Autopilot’ feature are some of the most common partially automated vehicles on the road today. A partially automated vehicle provides advanced driver assistance by controlling steering, acceleration/ deceleration, and braking; however, the human driver is still considered to be in control of the vehicle and is expected to be attentive. A previous UC Davis study found that Tesla vehicle owners with the Autopilot feature drove more than those without Autopilot, but the study did not determine whether higher VMT was caused by Autopilot. To better understand whether Autopilot influences how much individuals drive, the UC Davis research team interviewed 36 Tesla Autopilot users to evaluate whether they experienced changes to their travel, and the reasons for any reported changes. Key findings from the interviews are presented in this brief.