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Open Access Publications from the University of California
Cover page of Instantaneous Hybridization Factor: New Metric to More Accurately Model Hybrid-Electric Vehicle Emissions

Instantaneous Hybridization Factor: New Metric to More Accurately Model Hybrid-Electric Vehicle Emissions

(2021)

Hybrid-electric vehicles are a growing segment of the vehicle market and their share is anticipated to continue to grow as automakers seek to comply with increasingly stringent fuel economy standards. Hybrid vehicles generally use less fuel and produce fewer associated emissions than their conventional counterparts. However, their emissions patterns are unique; hybrids produce zero emissions during certain operations when the internal combustion engine is off, but produce particulate emission spikes when the engine starts or restarts. The overall air quality implications of more hybrid vehicles on the roads are not well understood.

Researchers at the University of Vermont collected real-time emissions and performance data from a hybrid vehicle operating in a variety of on-road conditions to develop a new parameter that could serve as the basis for future hybrid vehicle emissions models: the instantaneous hybridization factor. This parameter is the real-time proportion of a vehicle’s overall power use that comes from the hybrid propulsion system, and could be used in combination with known conventional vehicle emissions and operating data to derive more exact emissions estimates for hybrid vehicles. This research brief summarizes the findings and research implications from that work.

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Cover page of Developing Markets for Clean Heavy-Duty Trucks in Short-Haul Applications

Developing Markets for Clean Heavy-Duty Trucks in Short-Haul Applications

(2021)

California is pursuing multiple policies to spur the transition to a cleaner heavy-duty vehicle fleet. Achieving these targets will require massive change in the heavy-duty short-haul industry, and many unanswered questions remain. How do battery-electric heavy-duty trucks compare to diesel in everyday short-haul operations? How much would it cost to transition to a zero-emission truck fleet, and who would pay?

To begin to answer these questions, researchers at the National Center for Sustainable Transportation conducted a comprehensive analysis of the potential for zero-emission or near-zero-emission heavy-duty trucks to be used in short-haul drayage services. The researchers considered operational, economic, and environmental impacts through simulation modeling, interviews, case studies, stated preference surveys, and cost-effectiveness analyses.

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Cover page of The Monetary and Non-Monetary Factors Influencing Travel Choices in an Automated, Shared, and Electric Vehicle Future

The Monetary and Non-Monetary Factors Influencing Travel Choices in an Automated, Shared, and Electric Vehicle Future

(2021)

The transportation system is undergoing three revolutions: vehicle automation, electrification, and shared mobility. While these are still nascent trends, studies suggest that they could become ubiquitous in the coming decades. How these revolutionary changes transpire will have significant implications for transportation sustainability. A key factor will be whether autonomous vehicles are deployed as shared cars that serve many travelers such as in ridesourcing or ridehailing fleets, or as privately owned vehicles that could dramatically increase vehicle miles traveled and associated environmental impacts. To anticipate how these revolutions will affect future transportation, and to develop policy to shape that future, it is important to understand the various factors that influence individuals’ travel choices. These choices include whether to travel alone or with others, and whether to use a private vehicle or a shared one. Some of these factors are monetary, such as the cost of fuel, insurance, and a driver, while others are non-monetary, such as the travel time, comfort, and reliability of each transportation option. The significance of these non-monetary factors is poorly understood and often ignored.

Researchers at the University of California, Davis developed a framework for considering the monetary and non-monetary costs of future travel choices and used existing research to develop interim values for several non-monetary travel choice factors. This policy brief summarizes the findings from that research and provides policy implications.

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Cover page of The Sustainability of Alternative Last-Mile Delivery Strategies

The Sustainability of Alternative Last-Mile Delivery Strategies

(2021)

In the last decade, e-commerce has grown substantially and transformed individual shopping behaviors. Most shopping activities—at least part of the search, if not the purchase itself—now involve an online component. This has consequently changed commodity flow and urban goods distribution. E-commerce has the potential to reduce the negative impacts of shopping on the environment by substituting individual shopping trips to stores using personal cars with optimized truck deliveries. However, shopping behavior is often more complex than this one-to-one substitution.

Additionally, e-retailers entice consumers with free shipping, free returns, same-day, one-hour or two-hour expedited deliveries, and more in a quest for increased market share. These enhanced services result in additional distances driven, emissions, and operational costs for the e-retailer. The increasing customer expectations around lead time, delivery time, and return policy present a need for more sustainable delivery options, particularly for the “last mile” between the distribution center and the customer. Last-mile operators are considering alternatives to traditional diesel truck-based, door-to-door delivery such as use of alternative fuel (e.g., electric) vehicles, delivery from micro-hubs using cargo bikes, customer pickup at collection points, and crowdsourced deliveries. Researchers at the University of California, Davis developed models for e-commerce demand, last-mile delivery operations, and cost and sustainability assessment, then applied this modeling framework to a case study in Southern California to evaluate the potential impact of these strategies under different delivery scenarios. This policy brief summarizes findings from that research, along with policy implications.

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Cover page of Can Complete Streets Deliver on Sustainability?

Can Complete Streets Deliver on Sustainability?

(2021)

Complete streets are those designed not only for private vehicles, but also to enable safe access for all users, including pedestrians, bicyclists, motorists, and transit riders of all ages and abilities. Specific street designs vary based on the type of street. Complete streets are intended to improve non-motorized travel safety, reduce costs and environmental burdens, and create more livable, sustainable, and economically vibrant communities. Investment in complete streets projects is growing around the country with these goals in mind. However, there are limited data to verify the effectiveness of complete streets, and the indicators required for quantification of complete street performance are not yet agreed upon. Complete street sustainability indicators are important to assess whether a complete street conversion is achieving its goals and to support decision-making for complete street investment.

Researchers at the University of California, Davis and JCH Research used life cycle assessment, a modeling tool for evaluating a product or activity’s environmental impacts through all stages of its life, to quantify the environmental performance of complete streets. The researchers also reviewed the academic literature for social impact indicators, which have generally not been well developed in life cycle assessment applications. The researchers adapted these indicators to better consider equity, guided by interviews with a diverse set of stakeholders. Complete street typologies compiled from several sources were used to test and refine the life cycle assessment framework for complete street conversions. This policy brief summarizes the findings from that research.

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Cover page of Cost of Vehicle Ownership: Cost Parity Between Plug-in Electric Vehicles and Conventional Vehicles Is at Least a Decade Away

Cost of Vehicle Ownership: Cost Parity Between Plug-in Electric Vehicles and Conventional Vehicles Is at Least a Decade Away

(2021)

While plug-in electric vehicle (PEV) adoption has been rising over the past decade, with PEVs making-up about 7.8% of California’s new vehicle sales in 2019, the trend needs to quickly accelerate for the state to reach its goals of 100% zero-emission vehicle (ZEV) sales by 2035 and a zero-carbon economy by 2045. California has various incentive programs to encourage PEV adoption, but policymakers expect to phase these incentives out as PEVs reach cost parity with conventional internal combustion engine vehicles. Comparing the total cost of ownership—purchase price, operational costs, and resale value—of PEVs or other ZEVs with that of conventional vehicles can inform policy decisions about incentive programs and inform consumers’ purchase decisions, by accounting for PEVs’ higher purchase prices but lower fuel and maintenance costs.

Recent research has estimated that cost parity between PEVs and conventional vehicles will be achieved over the next decade. However, the timeline depends on each study’s assumptions about technology improvement and travel behavior. These studies often assign a single total cost of ownership to a specific vehicle model, ignoring the fact that costs can vary across households based on the type of vehicle adopted, travel behavior, access to charging and refueling facilities, gasoline and electricity prices, and other factors. Researchers at the University of California, Davis estimated PEVs’ total cost of ownership for the period of 2020–2030, their cost-competitiveness with conventional vehicles, and consequently the cost of electrification of California’s fleet of more than 30 million light-duty vehicles. The researchers analyzed six market segments, defined by household income and housing type, to account for the heterogeneity in total cost of ownership. The cost of electrification analysis also included fuel cell electric vehicles and was extended out to 2045 to align with California’s emission reduction goals. This policy brief summarizes findings from that research and provides policy implications.

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Cover page of Why are Some California Consumers Abandoning Electric Vehicle Ownership?

Why are Some California Consumers Abandoning Electric Vehicle Ownership?

(2021)

California has set an ambitious goal of 100% zero-emission vehicle sales by 2035. Most consumer research to date has focused on understanding the factors influencing the initial purchase of plug-in electric vehicles (PEVs). But for the market introduction of PEVs, which include both battery electric vehicles (BEVs) and plug-in hybrid electric vehicles (PHEVs), to be successful, subsequent vehicle purchases by initial adopters need to continue to be PEVs rather than conventional vehicles. Discontinuance, the act of abandoning a new technology after once being an adopter, could make achieving California’s goal more challenging.

Researchers at the University of California, Davis surveyed California PEV buyers two to seven years after they first purchased their electric vehicle to understand whether they have continued to choose PEVs with subsequent purchases, and if not, what factors may have led to their discontinuance of the technology. This policy brief summarizes the findings from that research and provides policy implications.

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Cover page of Stakeholder Perspectives on the Sustainable Transportation Implications of On-demand Ridehailing

Stakeholder Perspectives on the Sustainable Transportation Implications of On-demand Ridehailing

(2021)

There is much uncertainty over whether on-demand ridehailing services, namely Uber and Lyft, will worsen or alleviate existing transportation problems such as congestion, emissions, and inequities in access and mobility. For policymakers, transportation planners, and others in the transportation arena, these unknowns have created uncertainty over which policies would best steer ridehailing toward equitable and sustainable outcomes. To address these uncertainties, researchers at UC Davis assessed how stakeholders from different groups view the possible impacts of ridehailing and the policies that might best address those impacts. The researchers evaluated these questions through in-depth interviews with stakeholders from 38 agencies and organizations throughout California. Interviewees included transportation planners, members of state agencies, and representatives from non-profit organizations and the ridehailing industry. This policy brief summarizes those interviews, as well as findings from the research.

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Cover page of A Method of Identifying Critical Road Infrastructure for Maintaining Food Accessibility

A Method of Identifying Critical Road Infrastructure for Maintaining Food Accessibility

(2021)

A key purpose of the transportation system is to provide access to critical services such as grocery stores. Maintaining food access during an emergency or other disruption is all the more important, particularly for vulnerable households. Most people in the United States rely on the use of private automobiles for grocery shopping. Thus, disruptions to road networks due to heavy precipitation, flooding, or even major maintenance and repair projects present notable threats to accessibility. Regional planning models that address food accessibility issues (not all do) typically do not consider households’ familiarity with grocery locations. However, during a disruptive event, a household’s familiarity with at least one available route to a retail grocery location becomes paramount. Identifying the roadways that are most critical to food access can help decision makers devise strategies to mitigate the risks of food insecurity for vulnerable households and populations.

Researchers at the University of Vermont developed a methodology that provides an ordinal measure of demand-side food access. It takes into account the spatial distribution of both the origin and destination, the topology of the road network, and the characteristics of the roadway network such as capacities, volumes, and travel speeds. The analysis considers household familiarity with retail grocery locations, destination weighting to account for retail grocery characteristics (square footage), and origin weighting to account for household vulnerability. The researchers demonstrated the methodology using the travel demand model for Chittenden County, Vermont. This policy brief summarizes the findings from that research and provide policy implications.

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Cover page of User Perceptions of the Risks of Electric, Shared, and Automated Vehicles Remain Largely Unexplored

User Perceptions of the Risks of Electric, Shared, and Automated Vehicles Remain Largely Unexplored

(2021)

Advocates of electric, shared, and automated vehicles (e-SAVs) envision a future in which people no longer need to drive their privately owned, petroleum-fueled vehicles. Instead, for daily travel they rely on fleets of electric, automated vehicles that offer travel services, including the option to share, or “pool,” rides with strangers. The design, deployment, and operation of e-SAVs will require widespread willingness of users to share with strangers vehicles that are capable of fully automated driving. To achieve the environmental and societal goals of e-SAVs it is critical to first understand and address safety and security concerns of potential and actual users. Researchers at the University of California, Davis, reviewed the literature to understand potential users’ perceptions of safety and security risks posed by intertwined social and technical systems of e-SAVs and proposed a framework to advance research, policy, and system design. This policy brief summarizes the findings of that work and provides policy implications.

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