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Open Access Publications from the University of California
Cover page of Integrating Traffic Network Analysis and Communication Network Analysis at a Regional Scale to Support More Efficient Evacuation in Response to a Wildfire Event

Integrating Traffic Network Analysis and Communication Network Analysis at a Regional Scale to Support More Efficient Evacuation in Response to a Wildfire Event


As demonstrated by the Camp Fire evacuation, communications (city-to-city, city-to-residents) play important roles in coordinating traffic operations and safeguarding region-wide evacuation processes in wildfire events. This collaborative report across multiple domains (fire, communication and traffic), documents a series of simulations and findings of the wildfire evacuation process for resource-strapped towns in Northern California. It consists of: (1) meteorological and vegetation-status dependent fire spread simulation (cellular automata model); (2) agency-level and agency-to-residents communication simulation (system dynamics model); and (3) dynamic traffic assignment (spatial-queue model). Two case studies are conducted: one for the town of Paradise (and the surrounding areas) and another for the community of Bolinas. The data and models are based on site visits and interviews with local agencies and residents. The integrated simulation framework is used to assess the interdependencies among the natural environment, the evacuation traffic and the communication networks from an interdisciplinary point of view, to determine the performance requirements to ensure viable evacuation strategies under urgent, dynamic wildfire conditions. The case study simulations identify both potential traffic and communication bottlenecks. This research supports integrating fire, communication and traffic simulation into evacuation performance assessments.

Cover page of A Quantitative Investigation into the Impact of Partially Automated Vehicles on Vehicle Miles Travelled in California

A Quantitative Investigation into the Impact of Partially Automated Vehicles on Vehicle Miles Travelled in California


This project investigated changes in travel behavior by owners of partially automated electric vehicles. Partial automation can control vehicle speed and steering using sensors that monitor the external environment. The researchers used review results from survey responses including 940 users of partial automation, of which 628 who have Tesla Autopilot and 312 with systems from other automakers. Autopilot users report using automation more than users of other partial automation systems. Autopilot has the largest impact on travel, notably 36% of Autopilot users reporting more longdistance travel. Respondents who are younger, have a lower household income, use automation in a greater variety of traffic, roads, and weather conditions, and those who have pro-technology attitudes and outdoor lifestyles are more likely to report doing more long-distance travel. The project used propensity score matching to investigate whether automation leads to any increase in respondents’ annual vehicle miles travelled. For simplicity, the researchers focused only on the impact of Tesla Autopilot and found that automation results in an average of 4,884 more miles being driven per year.

Cover page of Homelessness in Transit Environments Volume II: Transit Agency Strategies and Responses

Homelessness in Transit Environments Volume II: Transit Agency Strategies and Responses


Transit settings represent sites of visible homelessness, especially since the advent of COVID-19, for many of the over 500,000 Americans unhoused each night. This report seeks to understand the scale of homelessness on transit and how transit agencies are responding to the problem. Part I describes the extent of homelessness on transit in several areas by using count data and synthesizing prior research. We find that transit serves as shelter for a high, though quite variable, share of unsheltered individuals, who are more likely than their unhoused peers elsewhere to be chronically unhoused and structurally disadvantaged. Part II provides detailed case studies of strategies taken by transit agencies around the country: hub of services, mobile outreach, discounted fares, and transportation to shelters. We summarize each strategy’s scope, implementation, impact, challenges, and lessons learned. Reviewing these strategies, we find value in collecting data more systematically, fostering external partnerships, keeping law enforcement distinct from routine homeless outreach, educating the public, and training transit staff—all in the context of a broader need for more housing and services.

Cover page of Do Electricity Prices Affect Electric Vehicle Adoption?

Do Electricity Prices Affect Electric Vehicle Adoption?


This report presents evidence that gasoline prices have a larger effect on demand for battery electric vehicles (BEVs) than do electricity prices in California. A spatially-disaggregated panel dataset of monthly BEV registration records was matched to detailed records of gasoline and electricity prices in California from 2014-2017, and the matched data was used to estimate the effect of energy prices on BEV demand. Two distinct empirical approaches (panel fixed-effects and a utility-border discontinuity) yield remarkably similar results: a given change in gasoline prices has roughly four times the effect on BEV demand as a similar percentage change in electricity prices.

Cover page of Transportation, Quality of Life, and Older Adults

Transportation, Quality of Life, and Older Adults


Driving rates decline with age as vision, health, and cognitive ability cause some older adults to give up driving. Many older adults first gradually limit their driving as they age and later cease driving. Using data from the Health and Retirement Study (HRS), which surveys 22,000 older Americans every two years, we modeled the extent to which older drivers limit and stop driving. The data are longitudinal, allowing analysis of changes in driving and residential location as well as cohort effects that could not be studied using standard, cross-sectional survey data that only allow comparisons of different people at one point in time. The analysis shows that decisions to limit and eventually stop driving vary in statistically significant ways with sex, age, and health conditions. These relationships also differ by birth cohort. More recent cohorts are less likely to stop and limit driving than older ones. To analyze the relationship between residential location and driving behavior, we linked the HRS data to census-tract level data from the US Census and a categorization of community types. We found that residential density and other urban built environment features are associated with changes in driving and vehicle ownership. HRS survey participants showed a greater propensity to reduce or give up driving if they resided in denser, more diverse, transit-oriented neighborhoods. People who prefer non-automotive modes of transportation may have been more likely than others to self-select into walkable and transit-rich areas. The findings should inform California’s strategic planning for aging and its community development policies. In addition to informing planning for the next generation of older Californians, this study demonstrated the utility of longitudinal information and models for the understanding of older populations and their travel.

Cover page of Driving California’s Transportation Emissions to Zero

Driving California’s Transportation Emissions to Zero


The purpose of this report is to provide a research-driven analysis of options that can put California on a pathway to achieve carbon-neutral transportation by 2045. The report comprises thirteen sections. Section 1 provides an overview of the major components of transportation systems and how those components interact. Section 2 discusses the impacts the COVID-19 pandemic has had on transportation. Section 3 discusses California’s current transportation-policy landscape. These three sections were previously published as a synthesis report. Section 4 analyzes the different carbon scenarios, focusing on “business as usual” (BAU) and Low Carbon (LC1). Section 5 provides an overview of key policy mechanisms to utilize in decarbonizing transportation. Section 6 is an analysis of the light-duty vehicle sector, section 7 is the medium- and heavy-duty vehicle sectors, section 8 is reducing and electrifying vehicle miles traveled, and section 9 is an analysis of transportation fuels and their lifecycle. The following sections are an analysis of external costs and benefits: section 10 analyzes the health impacts of decarbonizing transportation, section 11 analyzes equity and environmental justice, and section 12 analyzes workforce and labor impacts. Finally, future research needs are provided in section 13. The study overall finds that cost-effective pathways to carbon-neutral transportation in California exist, but that they will require significant acceleration in a wide variety of policies.

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Cover page of Benchmarking “Smart City” Technology Adoption in California: Developing and Piloting a Data Collection Approach

Benchmarking “Smart City” Technology Adoption in California: Developing and Piloting a Data Collection Approach


In recent years, “smart city” technologies have emerged that allow cities, counties, and other agencies to manage their infrastructure assets more effectively, make their services more accessible to the public, and allow citizens to interface with new web- and mobile-based operators of alternative service providers. This project reviews the academic literature and other sources on potential strengths, weaknesses, and risks associated with smart city technologies. No dataset was found that measures the adoption of such technologies by government agencies. To address this gap, a methodology was developed to guide data collection on the adoption of smart city technologies by urban transportation agencies and other service providers in California. The strategy used involved webscraping; interviews with experts, public agency, and senior level staff; and consultations with technology vendors. The approach was tested by assembling data on the adoption of smart city technologies in California by municipalities and other local public agencies.

Cover page of Hydrogen Infrastructure Requirements for Zero-Emission Freight Applications in California

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.

Cover page of Answers from the Margins: Participatory Planning with Disadvantaged Communities

Answers from the Margins: Participatory Planning with Disadvantaged Communities


The public mandate to engage the public in transportation planning processes is in the process of becoming more rigorous and democratic. Transportation agencies are recognizing the limitations of past modes of engagement and seek to connect more dynamically with the public, particularly with historically marginalized communities. Doing this work well is a topic of interest to a growing number of transportation professionals. This study identified four successful engagement processes with historically marginalized communities in California by surveying transportation professionals. Stakeholders at each site were interviewed and public documents from the processes were reviewed to identify common themes for positive public inclusion. Interviewees included community leaders, transportation staff, and consultants. Interviews were coded and analysis was conducted using a mobility justice and critical race studies framework. Ten key themes of successful community engagement with historically marginalized communities were identified. These themes are: (1) trust is crucial; (2) treat community-based organizations as equal partners; (3) pay community partners fairly; (3) let community-based organizations decide what good community engagement is; (5) translate technical jargon; (6) engage in community concerns beyond the scope of the project; (7) address major community concerns such as displacement, policing, and youth development; (8) know local histories of transportation injustice; (9) include the community in the final reporting process; and (10) follow-up on planning with implementation in a timely manner.

Cover page of To Pool or Not to Pool? Understanding the Time and Price Tradeoffs of OnDemand Ride Users – Opportunities, Challenges, and Social Equity Considerations for Policies to Promote Shared-Ride Services

To Pool or Not to Pool? Understanding the Time and Price Tradeoffs of OnDemand Ride Users – Opportunities, Challenges, and Social Equity Considerations for Policies to Promote Shared-Ride Services


On-demand mobility services including transportation network companies (also known as ridesourcing and ridehailing) like Lyft and Uber are changing the way that people travel by providing dynamic mobility that can supplement public transit and personal-vehicle use. However, TNC services have been found to contribute to increasing vehicle mileage, traffic congestion, and greenhouse gas emissions. Pooling rides ⎯ sharing a vehicle by multiple passengers to complete journeys of similar origin and destination ⎯ can increase the average vehicle occupancy of TNC trips and thus mitigate some of the negative impacts. Several mobility companies have launched app-based pooling services in recent years including app-based carpooling services (e.g., Waze Carpool, Scoop) that match drivers with riders; pooled on-demand ride services (e.g., Uber Pool and Lyft Shared rides) that match multiple TNC users; and microtransit services (e.g., Bridj, Chariot, Via) that offer on-demand, flexibly routed service, typically in larger vehicles such as vans or shuttles. However, information on the potential impacts of these options is so far limited. This research employs a general population stated preference survey of four California metropolitan regions (Los Angeles, Sacramento, San Diego, and the San Francisco Bay Area) in Fall 2018 to examine the opportunities and challenges for drastically expanding the market for pooling, accounting for differences in emergent travel behavior and preferences across the four metropolitan regions surveyed. The travel profiles, TNC use patterns, and attitudes and perceptions of TNCs and pooling are analyzed across key socio-demographic attributes to enrich behavioral understanding of marginalized and price sensitive users of on-demand ride services. This research further develops a discrete choice model to identify significant factors influencing a TNC user’s choice to pool or not to pool, as well as estimating a traveler’s value of time (VOT) across different portions of a TNC trip. This research provides key insights and social equity considerations for policies that could be employed to reduce vehicle miles traveled and emissions from passenger road transportation by incentivizing the use of pooled on-demand ride services and public transit