Skip to main content
Open Access Publications from the University of California

The primary mission of the Institute is research - cross-disciplinary inquiries into emerging transportation issues with great societal significance. It draws upon campus researchers and graduate students from a variety of disciplines, and also upon other universities and research centers around the world.

Low-Carbon Energy Generates Public Health Savings in California


California's goal to reduce greenhouse gas (GHG) emissions to a level that is 80 % below 1990 levels by the year 2050 will require adoption of low-carbon energy sources across all economic sectors. In addition to reducing GHG emissions, shifting to fuels with lower carbon intensity will change concentrations of short-lived conventional air pollutants, including airborne particles with a diameter of less than 2.5 µm (PM2.5) and ozone (O3). Here we evaluate how business-as-usual (BAU) air pollution and public health in California will be transformed in the year 2050 through the adoption of low-carbon technologies, expanded electrification, and modified activity patterns within a low-carbon energy scenario (GHG-Step). Both the BAU and GHG-Step statewide emission scenarios were constructed using the energy–economic optimization model, CA-TIMES, that calculates the multi-sector energy portfolio that meets projected energy supply and demand at the lowest cost, while also satisfying scenario-specific GHG emissions constraints. Corresponding criteria pollutant emissions for each scenario were then spatially allocated at 4 km resolution to support air quality analysis in different regions of the state. Meteorological inputs for the year 2054 were generated under a Representative Concentration Pathway (RCP) 8.5 future climate. Annual-average PM2.5 and O3 concentrations were predicted using the modified emissions and meteorology inputs with a regional chemical transport model. In the final phase of the analysis, mortality (total deaths) and mortality rate (deaths per 100 000) were calculated using established exposure-response relationships from air pollution epidemiology combined with simulated annual-average PM2.5 and O3 exposure. Net emissions reductions across all sectors are −36 % for PM0.1 mass, −3.6 % for PM2.5 mass, −10.6 % for PM2.5 elemental carbon, −13.3 % for PM2.5 organic carbon, −13.7 % for NO x , and −27.5 % for NH3. Predicted deaths associated with air pollution in 2050 dropped by 24–26 % in California (1537–2758 avoided deaths yr−1) in the climate-friendly 2050 GHG-Step scenario, which is equivalent to a 54–56 % reduction in the air pollution mortality rate (deaths per 100 000) relative to 2010 levels. These avoided deaths have an estimated value of USD 11.4–20.4 billion yr−1 based on the present-day value of a statistical life (VSL) equal to USD 7.6 million. The costs for reducing California GHG emissions 80 % below 1990 levels by the year 2050 depend strongly on numerous external factors such as the global price of oil. Best estimates suggest that meeting an intermediate target (40 % reduction in GHG emissions by the year 2030) using a non-optimized scenario would reduce personal income by USD 4.95 billion yr−1 (−0.15 %) and lower overall state gross domestic product by USD 16.1 billion yr−1 (−0.45 %). The public health benefits described here are comparable to these cost estimates, making a compelling argument for the adoption of low-carbon energy in California, with implications for other regions in the United States and across the world.

Cover page of Societal lifetime cost of hydrogen fuel cell vehicles

Societal lifetime cost of hydrogen fuel cell vehicles


Various alternative fuels and vehicles have been proposed to address transportation related environmental and energy issues such as air pollution, climate change and energy security. Hydrogen fuel cell vehicles (FCVs) are widely seen as an attractive long term option, having zero tailpipe emissions and much lower well to wheels emissions of air pollutants and greenhouse gases than gasoline vehicles. Hydrogen can be made from diverse primary resources such natural gas, coal, biomass, wind and solar energy, reducing petroleum dependence. Although these potential societal benefits are often cited as a rationale for hydrogen, few studies have attempted to quantify them. This paper attempts to answer the following research questions: what is the magnitude of externalities and other social costs for FCVs as compared to gasoline vehicles? Will societal benefits of hydrogen and FCVs make these vehicles more competitive with gasoline vehicles? How does this affect transition timing and costs for hydrogen FCVs? We employ societal lifetime cost as an important measure for evaluating hydrogen fuel cell vehicles (FCVs) from a societal welfare perspective as compared to conventional gasoline vehicles. This index includes consumer direct economic costs (initial vehicle cost, fuel cost, and operating and maintenance cost) over the entire vehicle lifetime, and also considers external costs resulting from air pollution, noise, oil use and greenhouse gas emissions over the full fuel cycle and vehicle lifetime. Adjustments for non-cost social transfers such as taxes and fees, and producer surplus associated with fuel1 and vehicle are taken into account as well. Unlike gasoline, hydrogen is not widely distributed to vehicles today, and fuel cell vehicles are still in the demonstration phase. Understanding hydrogen transition issues is the key for assessing the promise of hydrogen. We have developed several models to address the issues associated with transition costs, in particular, high fuel cell system costs and large investments for hydrogen infrastructure in the early stages of a transition to hydrogen. We analyze three different scenarios developed by the US Department of Energy for hydrogen and fuel cell vehicle market penetration from 2010 to 2025. We employ a learning curve model characterized by three multiplicative factors (technological change, scale effect, and learning-by-doing) for key fuel cell stack components and auxiliary subsystems to estimate how fuel cell vehicle costs change over time. The delivered hydrogen fuel cost is estimated using the UC Davis SSCHISM hydrogen supply pathway model, and most vehicle costs are estimated using the Advanced Vehicle Cost and Energy Use Model (AVCEM). To estimate external costs, we use AVCEM and the Lifecycle Emissions Model (LEM). We estimate upstream air pollution damage costs with estimates of emissions factors from the LEM and damage factors with a simple normalized dispersion term from a previous analysis of air pollution external costs. This approach allows us to estimate the total societal cost of hydrogen FCVs compared to gasoline vehicles, and to examine our research questions. To account for uncertainties, we examine hydrogen transition costs for a range of market penetration rates, externality evaluations, technology assumptions, and oil prices. Our results show that although the cost difference between FCVs and gasoline vehicles is initially very large, FCVs eventually become lifetime cost competitive with gasoline vehicles as their production volume increases, even without accounting for externalities. Under the fastest market penetration scenario, the cumulative investment needed to bring hydrogen FCVs to lifetime cost parity with gasoline vehicles is about $14-$24 billion, and takes about 12 years, when we assume reference and high gasoline prices. However, when externalities and social transfers are considered, the buy-down cost of FCVs in the US could about $2-$5 billion less with medium valuation of externalities and $8-$15 billion less with high valuation of externalities. With global accounting and high valuation of externalities, we would have $7-$12 billion savings on the buy-down cost compared to a case without externality costs. Including social costs could make H2 FCVs competitive sooner, and at a lower overall societal cost.

Cover page of Review of technical literature and trends related to automobile mass-reduction technology

Review of technical literature and trends related to automobile mass-reduction technology


Past automotive trends, ongoing technology breakthroughs, and recent announcements by automakers make it clear that reducing the mass of automobiles is a critical technology objective for vehicle performance, carbon dioxide (CO2) emissions, and fuel economy. Vehicle mass-reduction technology offers the potential to reduce the mass of vehicles without compromise in other vehicle attributes, like acceleration, size, cargo capacity, or structural integrity. As regulatory agencies continue to assess more stringent CO2 and fuel economy standards for the future, it is unclear the exact extent to which vehicle mass-reduction technology will be utilized alongside other efficiency technologies like advanced combustion and hybrid system technology. This report reviews ongoing automotive trends, research literature, and advanced concepts for vehicle mass optimization in an attempt to better characterize where automobiles – and their mass in particular – might be headed.

Cover page of Anticipating plug-in hybrid vehicle energy impacts in California: Constructing consumer-informed recharge profiles

Anticipating plug-in hybrid vehicle energy impacts in California: Constructing consumer-informed recharge profiles


Plug-in hybrid electric vehicles (PHEVs) can be powered by gasoline, grid electricity, or both. To explore potential PHEV energy impacts, a three-part survey instrument collected data from new vehicle buyers in California. We combine the available information to estimate the electricity and gasoline use under three recharging scenarios. Results suggest that the use of PHEV vehicles could halve gasoline use relative to conventional vehicles. Using three scenarios to represent plausible conditions on PHEV drivers’ recharge patterns (immediate and unconstrained, universal workplace access, and off-peak only), tradeoffs are described between the magnitude and timing of PHEV electricity use. PHEV electricity use could be increased through policies supporting non-home recharge opportunities, but this increase occurs during daytime hours and could contribute to peak electricity demand. Deferring all recharging to off-peak hours could eliminate all additions to daytime electricity demand from PHEVs, although less electricity is used and less gasoline displaced.

Cover page of Bikesharing in Europe, the Americas, and Asia: Past, Present, and Future

Bikesharing in Europe, the Americas, and Asia: Past, Present, and Future


Growing concerns over global motorization and climate change have led to increasing interest in sustainable transportation alternatives, such as bikesharing (the shared use of a bicycle fleet). Since 1965, bikesharing has grown across the globe on four continents including: Europe, North America, South America, and Asia (including Australia). Today, there are approximately 100 bikesharing programs operating in an estimated 125 cities around the world with over 139,300 bicycles. Bikesharing’s evolution is categorized into three generations: 1) White Bikes (or Free Bike Systems); 2) Coin-Deposit Systems; and 3) IT-Based Systems. In this paper, the authors propose a fourth-generation: “Demand-Responsive, Multi-Modal Systems.” A range of existing bikesharing business models (e.g., advertising) and lessons learned are discussed including: 1) bicycle theft and vandalism; 2) bicycle redistribution; 3) information systems (e.g., real-time information); 4) insurance and liability concerns; and 5) pre-launch considerations. While limited in number, several studies have documented bikesharing’s social and environmental benefits including reduced auto use, increased bicycle use, and a growing awareness of bikesharing as a daily mobility option. Despite bikesharing’s ongoing growth, obstacles and uncertainty remain, including: future demand; safety; sustainability of business models; limited cycling infrastructure; challenges to integrating with public transportation systems; technology costs; and user convenience (e.g., limited height adjustment on bicycles, lack of cargo space, and exposure to weather conditions). In the future, more research is needed to better understand bikesharing’s impacts, operations, and business models in light of its reported growth and benefits.

Cover page of Envisioning Parking Strategies for the Post-Automobile City

Envisioning Parking Strategies for the Post-Automobile City


Parking policies and regulations are important tools in planning for the governance of urban mobility. The proper design and location of parking facilities, in fact, contributes to an efficient use of the transportation system (or it may reduce its efficiency, when these infrastructures are not properly planned). This paper discusses the role of parking as part of the policy packages for strategic planning aimed at increasing the sustainability of urban and metropolitan areas. In particular, the integration of parking strategies in a comprehensive vision for the future of a city may significantly improve the allocation of resources and the reduction of the overall environmental externalities.

The role of parking in the strategic planning of cities is discussed through the analysis of several recent projects in the city of Bari (Italy). The paper discusses the way these projects are linked (or eventually not linked) to broader strategies for urban mobility, and how they might be coordinated into policy packages that promote more sustainable transportation. The use of an integrated land use transportation modeling approach to simulate the long-term evolution of the urban area may significantly contribute to estimate the long-term effects of the proposed policies. This approach may successfully support the process of policy evaluation and the selection of the optimal strategies to implement.

Cover page of Climate and Transportation Solutions: Findings from the 2009 Asilomar Conference on Transportation and Energy Policy

Climate and Transportation Solutions: Findings from the 2009 Asilomar Conference on Transportation and Energy Policy


Climate change has fully entered the public consciousness, but what to do and how fast to do it remains intensely controversial. Questions about how to mold transportation policy to help achieve climate goals were the focus of the Asilomar conference hosted by the UC Davis Institute of Transportation Studies in July 2009. Two hundred leaders and experts were assembled from the automotive and energy industries, start-up technology companies, public interest groups, academia, national energy laboratories in the United States, and governments from around the world. Three broad strategies for reducing greenhouse gas emissions were investigated: reducing vehicle travel, improving vehicle efficiency, and reducing the carbon content of fuels. This book examines strategies, technologies, and policies to reduce GHGs and oil use. The book is aimed at researchers, policymakers, and students interested in the future of energy and transportation.

Individual chapters of this book are available to download free of charge. A paperback version of the book will be available soon on

Cover page of An Analysis of Near-Term Hydrogen Vehicle Rollout Scenarios for Southern California

An Analysis of Near-Term Hydrogen Vehicle Rollout Scenarios for Southern California


There is rapid, ongoing progress in development of both fuel cell vehicle technology, and hydrogen refueling systems. Although hydrogen and fuel cell vehicles are not yet ready for full commercial deployment, they are ready to take the next step toward commercialization. This is widely seen as a “networked demonstration” in a localized region or “lighthouse city,” involving hundreds to thousands of vehicles and an early network of tens of refueling stations. Because of California’s ZEV regulation, Southern California has been proposed as an ideal site for this early introduction of hydrogen vehicles and is a major focus of interest worldwide.

Developing a successful early hydrogen refueling network in Southern California, even at the relatively small scale envisioned for 2009-2017, requires a coordinated strategy, where vehicles and stations are introduced together. A major question is how many stations to build, what type of stations, and where to locate them. Key concerns include fuel accessibility, customer convenience, quality of refueling experience, network reliability, cost, and technology choice.

In this paper, a strategy of “clustering” is explored. Clustering refers to the focused introduction of hydrogen vehicles in defined geographic areas such as smaller cities (e.g. Santa Monica, Irvine) within a larger region (e.g. LA Basin). By focusing initial customers in a few small areas, station infrastructure can be similarly focused, reducing the number of stations necessary to achieve a given level of convenience as measured by the travel time from home to the nearest station and “diversion time” explained later. We evaluate the potential for clustering to improve customer convenience, reduce refueling network costs, and enhance system reliability.

Cover page of Are Batteries Ready for Plug-in Hybrid Buyers?

Are Batteries Ready for Plug-in Hybrid Buyers?


The notion persists that battery technology and cost remain as barriers to commercialization of electric-drive passenger vehicles. Within the context of starting a market for plug-in hybrid electric vehicles (PHEVs), we explore two aspects of the purported problem: (1) PHEV performance goals and (2) the abilities of present and near-term battery chemistries to meet the resulting technological requirements. We summarize evidence stating that battery technologies do not meet the requirements that flow from three sets of influential PHEV goals due to inherent trade-offs among power, energy, longevity, cost, and safety. However, we also show that part of this battery problem is that those influential goals are overly ambitious compared to goals derived from consumers’ PHEV designs. We elicited PHEV designs from potential early buyers among U.S. new car buyers; most of those who are interested in a PHEV are interested in less technologically advanced PHEVs than assumed by experts. Using respondents’ PHEV designs, we derive peak power density and energy density requirements and show that current battery chemistries can meet them. By assuming too aggressive PHEV goals, existing policy initiatives, battery research, and vehicle development programs mischaracterize the batteries needed to start commercializing PHEVs. To answer the question whether batteries are ready for PHEVs, we must first answer the question, ‘‘whose PHEVs?’’

Cover page of Fragmentation of China’s landscape by roads and urban areas

Fragmentation of China’s landscape by roads and urban areas


China’s major paved road-ways (national roads, provincial roads, and county roads), railways and urban development are rapidly expanding. A likely consequence of this fast-paced growth is landscape fragmentation and disruption of ecological flows. In order to provide ecological information to infrastructure planners and environmental managers for use in landscape conservation, land-division from development must be measured. We used the effective- mesh-size (Meff) method to provide the first evaluation of the degree of landscape division in China, caused by paved roads, railways, and urban areas. Using Meff, we found that fragmentation by major transportation systems and urban areas in China varied widely, from the least-impacted west to the most impacted south and east of China. Almost all eastern provinces and counties, especially areas near big cities, have high levels of fragmentation. Several eastern-Chinese provinces and biogeographic regions have among the most severe landscape fragmentation in the world, while others are comparable to the leastdeveloped areas of Europe and California. Threatened plant hotspots and areas with high mammal species diversity occurred in both highly fragmented and less fragmented areas, though future road development threatens already moderately divided landscapes. To conserve threatened biodiversity and landscapes, we recommend that national and regional planners in China consider existing land division before making decisions about further road development and improvement.