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Open Access Publications from the University of California

Recent Work

The Transportation Sustainability Research Center fosters research, education, and outreach so that transportation can serve to improve economic growth, environmental quality and equity. Co-Directors are Dan Kammen, the Class of 1935 Distinguished Professor of Energy at UC Berkeley, Tim Lipman, PhD, and Susan Shaheen, PhD. The groups participating in this effort are the:

University of California Transportation Center
University of California Energy Institute
Institute of Transportation Studies
Energy and Resources Group
Center for Global Metropolitan Studies
Berkeley Institute of the Environment

Cover page of Strategies to Overcome Transportation Barriers for Rent Burdened Oakland Residents

Strategies to Overcome Transportation Barriers for Rent Burdened Oakland Residents

(2021)

Shared mobility is gaining traction in the transportation community as a potentially more environmentally friendly alternative to automobile travel and complement to public transit. However, adoption and use of shared mobility by low-income individuals lags behind other demographic groups. Additional research is needed to better understand the transportation needs of low-income travelers and how public agencies, community-based organizations, and shared mobility operators can work together to best serve those needs.

This research fills gaps in understanding the potential policy strategies that could be effective at increasing the access, awareness, and use of shared mobility by low-income individuals. We employ Oakland, California as our primary study site (see Figure 1 and Table 1 for more detail). In this report, we present our findings on barriers to shared mobility from a review of existing shared mobility social equity initiatives, expert interviews (n=13) and focus groups with rent burdened residents of East Oakland (n=24). We further investigate barriers and implications for transportation use in an online survey (n=177), as well as longitudinal panel of phone and video interviews (n=31) with rent burdened Oakland residents. Rent burden refers to the percentage of income spent on rent and can more widely capture the population of Oakland residents who are struggling to keep up with rising housing costs.

Cover page of Bridging the Income and Digital Divide with Shared Automated Electric Vehicles

Bridging the Income and Digital Divide with Shared Automated Electric Vehicles

(2021)

This research investigates strategies to improve the mobility of low-income travelers by incentivizing the use of electric SAVs (SAEVs) and public transit. We employ two agent-based simulation engines, an activity-based travel demand model of the San Francisco Bay Area, and vehicle movement data from the San Francisco Bay Area and the Los Angeles Basin to model emergent travel behavior of commute trips in response to subsidies for TNCs and public transit. Sensitivity analysis was conducted to assess the impacts of different subsidy scenarios on mode choices, TNC pooling and match rates, vehicle occupancies, vehicle miles traveled (VMT), and TNC revenues. The scenarios varied in the determination of which travel modes and income levels were eligible to receive a subsidy of $1.25, $2.50, or $5.00 per ride. Four different mode-specific subsidies were investigated, including subsidies for 1) all TNC rides, 2) pooled TNC rides only, 3) all public transit rides, and 4) TNC rides to/from public transit only. Each of the four modespecific subsidies were applied in scenarios which subsidized travelers of all income levels, as well as scenarios that only subsidized low-income travelers (earning less than $50,000 annual household income). Simulations estimating wait times for TNC trips in both the San Francisco Bay Area and Los Angeles regions also revealed that wait times are distributed approximately equally across low- and high-income trip requests.

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

(2021)

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

Cover page of Roundtrip Carsharing in New York City: An Evaluation of a Pilot Program and System Impacts

Roundtrip Carsharing in New York City: An Evaluation of a Pilot Program and System Impacts

(2021)

The study found that roundtrip carsharing in NYC mostly serves as a substitute for car rental, other personal vehicle modes, and personal vehicle ownership. The analysis showed that the broader pilot program had a modest impact on user behavior through carsharing (i.e., reduced vehicle ownership, reduced VMT, and mode shift). It also found that the pilot program likely expanded the membership base of carsharing to demographic cohorts that are traditionally underrepresented in carsharing populations (i.e., increased participation by lower education levels, lower household incomes, minority demographics). The study also examined vehicle ownership impacts and changes in vehicle miles traveled (VMT) and greenhouse gas (GHG) emissions. Analysis of survey and activity data indicated that 7% of NYC carsharing members avoided a car purchase, and 0.61% of members got rid of a car they already owned due to carsharing. Across the membership base, VMT was reduced by 7% and GHG emissions were reduced by 6%. These findings showed that carsharing reduced VMT and delivered associated environmental benefits within NYC, and more broadly had a substantive impact on travel behavior among members in form of mode shift away from personal automotive modes.

Cover page of AVCEM DOCUMENTATION PART 3: REVIEW OF THE LITERATURE ON THE PRIVATE AND SOCIAL LIFETIME COST OF ELECTRIC AND ALTERNATIVE-FUEL VEHICLE COSTS

AVCEM DOCUMENTATION PART 3: REVIEW OF THE LITERATURE ON THE PRIVATE AND SOCIAL LIFETIME COST OF ELECTRIC AND ALTERNATIVE-FUEL VEHICLE COSTS

(2021)

In order to assess the state of knowledge of the private and social lifetime cost (LC) of conventional and alternative-powertrain vehicles (mainly electric vehicles), we reviewed and evaluated 190 LC studies published between 2000 and 2020. Our main objective was to determine which aspects of the LC of motor vehicles were well researched and well analyzed, and which aspects were less well researched and analyzed and accordingly would benefit most from a focused new research effort. 

 In general, few studies are comprehensive (cover all components of the LC), original (as opposed to reliant on other work), and detailed (as opposed to being based on simple assumptions).

A spreadsheet accompanying this report evaluates all of the studies.

  • 1 supplemental file
Cover page of Urban Air Mobility: History, Ecosystem, Market Potential, and Challenges

Urban Air Mobility: History, Ecosystem, Market Potential, and Challenges

(2021)

Since the early 20th century, inventors have conceptualized “plane cars” and other urban aerial transportation. Emerging innovations in electrification, automation, and other technologies are enabling new opportunities for on-demand air mobility, business models, and aircraft design. Urban air mobility (UAM) envisions a safe, sustainable, affordable, and accessible air transportation system for passenger mobility, goods delivery, and emergency services within or traversing metropolitan areas. This research employed a multi-method approach comprised of 106 interviews with thought leaders and two stakeholder workshops to construct the history, ecosystem, state of the industry, and potential evolution of UAM. The history, current developments, and anticipated milestones of UAM can be classified into six phases: 1) “flying car” concepts from the early 1910s to 1950s, 2) early UAM operations using scheduled helicopter services from the 1950s to 1980s, 3) re-emergence of on-demand services starting in the 2010s, 4) corridor services using vertical take-off and landing (VTOL) envisioned for the 2020s, 5) hub and spoke services, and 6) point-to-point services. In the future, UAM could face several barriers to growth and mainstreaming, such as the existing regulatory environment; community acceptance; and concerns about safety, noise, social equity, and environmental impacts. UAM also could be limited by infrastructure and airspace management needs, as well as business model constraints. The paper concludes with recommendations for future research on sustainability, social and economic impacts, airspace integration, and other topics.

Cover page of Developing Transportation Response Strategies for Wildfire Evacuations via an Empirically Supported Traffic Simulation of Berkeley, California

Developing Transportation Response Strategies for Wildfire Evacuations via an Empirically Supported Traffic Simulation of Berkeley, California

(2021)

Government agencies must make rapid and informed decisions in wildfires to safely evacuate people. However, current evacuation simulation tools for resource-strapped agencies largely fail to compare possible transportation responses or incorporate empirical evidence from past wildfires. Consequently, we employ online survey data from evacuees of the 2017 Northern California Wildfires (n=37), the 2017 Southern California Wildfires (n=175), and the 2018 Carr Wildfire (n=254) to inform a policy-oriented traffic evacuation simulation model. We test our simulation for a hypothetical wildfire evacuation in the wildland urban interface (WUI) of Berkeley, California. We focus on variables including fire speed, departure time distribution, towing of items, transportation mode, GPS-enabled rerouting, phased evacuations (i.e., allowing higher-risk residents to leave earlier), and contraflow (i.e., switching all lanes away from danger).

 

We found that reducing household vehicles (i.e., to 1 vehicle per household) and increasing GPS-enabled rerouting (e.g., 50% participation) lowered exposed vehicles (i.e., total vehicles in the fire frontier) by over 50% and evacuation time estimates (ETEs) by about 30% from baseline. Phased evacuations with a suitable time interval reduced exposed vehicles most significantly (over 90%) but produced a slightly longer ETE. Both contraflow (on limited links due to resource constraints) and slowing fire speed were effective in lowering exposed vehicles (around 50%), but not ETEs. Extended contraflow can reduce both exposed vehicles and ETEs. We recommend agencies develop a communication and parking plan to reduce evacuating vehicles, create and communicate a phased evacuation plan, and build partnerships with GPS-routing services.

Cover page of Understanding the Willingness to Share Resources in the Hurricane Irma Evacuation: A Multi-Modeling Approach

Understanding the Willingness to Share Resources in the Hurricane Irma Evacuation: A Multi-Modeling Approach

(2021)

Recent technological improvements have greatly expanded the sharing economy (e.g., Airbnb, Lyft, and Uber), coinciding with growing need for transportation and sheltering resources in evacuations. To understand influencers on sharing willingness in evacuations, we employed a multi-modeling approach across four sharing scenarios using three model types: 1) four binary logit models that capture each scenario separately; 2) a multi-choice latent class choice model (LCCM) that jointly estimates multiple scenarios via latent classes; and 3) a portfolio choice model (PCM) that estimates dimensional dependency. We tested our approach by employing online survey data from 2017 Hurricane Irma evacuees (n=368).

The multi-model approach uncovered behavioral nuances undetectable with a single model. First, the multi-choice LCCM and PCM models uncovered scenario correlation, specifically willingness to share for both transportation scenarios and both sheltering scenarios. Second, the multi-choice LCCM found three classes – transportation sharers, adverse sharers, and interested sharers. Transportation sharers were more likely to be female, lower-income, and residents of Southwest Florida compared to adverse sharers. Interested sharers were more likely to be male, long-time residents, and higher-income compared to adverse sharers. Third, families with children were unwilling to share regardless of the model, while spare capacity (i.e., seatbelts, spare beds) had a positive but somewhat insignificant influence on sharing. Fourth, experienced home sharers were more willing to share shelter in the binary logit and PCM models. We suggest that local agencies consider holistic sharing mechanisms across resource types and time (i.e., before, during, and after a hurricane evacuation).

Cover page of Future of Public Transit and Shared Mobility: Scenario Planning for COVID-19 Recovery

Future of Public Transit and Shared Mobility: Scenario Planning for COVID-19 Recovery

(2021)

In 2020, the novel coronavirus (COVID-19) pandemic enveloped the world, leading to a public health crisis that profoundly changed allaspects of society, especially multiple sectors in transportation such as public transit and shared mobility. With so much uncertaintyabout the future of travel, the transportation sector needs to move rapidly to shape the nature of public transit and shared mobilityservices during the COVID-19 recovery period. Consequently, the University of California Institute of Transportation Studies (UC ITS) and the Transportation Research Board’s (TRB) Executive Committee launched a scenario planning exercise from June to September 2020 involving 36 transportation experts. The exercise resulted in a series of policy options and research directions across three timeframes (i.e., within 12 months, one to three years, four to six years) that could guide the recovery of the public transit and shared mobility industries. This report offers several key takeaways. First, external forces beyond COVID-19 (e.g., economy, political will, etc.) will significantly drive the future of public transit and shared mobility and determine the effectiveness and feasibility of any policy strategies. Second, while public transit and shared mobility face a dire future in the short run, steps can be taken immediately to reduce the effects of the current crisis, while also laying the groundwork for more sustainable transportation in the future beyond COVID-19. Actions taken to only address the current crisis will not prepare public transit and shared mobility for the future. Finally, future policies and actions will not be effective without in-depth analysis and development. Research and lessons learned from demonstration and pilot projects will be critical for crafting policies, identifying all positive and negative outcomes, and shaping actions toward a future transportation system that is more resilient, socially equitable, and environmentally friendly.