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Open Access Publications from the University of California


Sustainable Transportation Energy Pathways (STEPS) is a four-year (2015-2018) multidisciplinary research consortium, part of the Institute of Transportation Studies at the University of California, Davis.

Sustainable Transportation Energy Pathways (STEPS)

There are 5 publications in this collection, published between 2015 and 2021.
Research Reports (5)

The Potential to Build Current Natural Gas Infrastructure to Accommodate the Future Conversion to Near-Zero Transportation Technology

The emergence of natural gas as an abundant, inexpensive fuel in the United States has highlighted the possibility that natural gas could play a significant role in the transition to low carbon fuels. Natural gas is often cited as a “bridge” to low carbon fuels in the transportation sector. Major corporations are already investing billions of dollars to build infrastructure to feed natural gas into the U.S. trucking industry and expand the use of natural gas in fleets. In the state of California, natural gas fueling infrastructure is expanding, especially in and around the ports of Los Angeles and Long Beach. The use of natural gas fueled medium and heavy duty fleets is currently on an upswing. The authors examine the precise natural gas infrastructure that is economically and technologically synergistic for both natural gas and renewable natural gas in the near-term, and alternative fuels like renewable natural gas (RNG) and hydrogen in the long term. In particular, the authors examine optimum paths for developing infrastructure in the near-term that will accommodate alternative fuels once they become available at the commercial scale. The original design of the Low Carbon Fuel Standard (LCFS) provides time for the development of advanced, near zero technologies. The authors consider the credits from the LCFS in our analysis.

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Hydrogen Infrastructure Requirements for Zero-Emission Freight Applications in California

Zero-emission vehicles are seen as key technologies for reducing freight- related air pollution and greenhouse gas emissions. California’s 2016 Sustainable Freight Action Plan established a target of 100,000 zero-emission freight vehicles utilizing renewable fuels by 2030. Hydrogen fuel cell vehicles are a promising zero-emission technology, especially for applications where batteries might be difficult to implement, such as heavy-duty trucks, rail, shipping and aviation. However, California’s current hydrogen infrastructure is sparse, with about 25 stations, primarily sited to serve fuel cell passenger vehicles and buses. New infrastructure strategies will be critical for implementing hydrogen freight applications. The researchers analyzed hydrogen infrastructure requirements, focusing on hydrogen fuel cells in freight applications, using a California-specific EXCEL-based scenario model developed under the Sustainable Transportation Energy Pathways program (STEPS) at the Institute of Transportation Studies at UC Davis (Miller et al, 2017). Hydrogen vehicle adoption and demand was estimated for trucks, rail, shipping, and aviation, for a range of scenarios out to 2050.

Estimating the Costs of New Mobility Travel Options: Monetary and Non-Monetary Factors

UC Davis researchers have developed a cost model of travel choices that individuals make related to urban vehicle travel. These choices can include deciding to own, ride in, and drive a private vehicle or use pooled or solo ridesourcing (e.g., Uber). The model considers both monetary and non-monetary factors that affect travel choice. Monetary factors include the costs of purchasing, maintaining, and fueling different types of privately owned vehicles; and the cost of using ridesourcing services. Non-monetary (or “hedonic”) factors include travel time, parking time/inconvenience, willingness to drive or be a passenger in a driven or automated vehicle, and willingness to travel with strangers. The travel choices affected by these factors impact broader society through traffic congestion, pollution, greenhouse gas emissions, accidents, etc. and thus may be an important focus of policy. This report reviews recent literature, considers factors affecting travel choices, and reports, on a conjoint pilot survey or stated preferences. Finally, it considers approaches to apply time value to factors that are not typically associated with specific trips, such as time spent on vehicle maintenance and parking. The results should enable a deeper understanding of the likelihood that individuals will own and use private vehicles or use shared (solo and pooled) ridesourcing, and how automated vehicle services could affect these choices in the future. The study also highlights additional research needs, such as a large scale stated preference study covering more factors than have been included in previous studies.

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