UC Davis Institute of Transportation Studies

The UC Davis Campus Travel Survey is an annual survey led by Transportation Services (TS)—formerly known as Transportation and Parking Services (TAPS)—and the National Center for Sustainable Transportation (NCST), part of the Institute of Transportation Studies (ITS) at UC Davis. It collects a rich set of data about travel to the UC Davis campus, demographics, and attitudes toward travel.

The 2023-24 survey collected data from 4,774 people affiliated with UC Davis about their travel to campus during a single week in October and November 2023. It used a stratified random sampling method with the intent to gather a representative sample of the campus population. About 14 percent of those invited responded to this year’s survey. For the statistics presented throughout this report, we weight the responses by campus role (freshman, sophomore, junior, senior, Master’s, PhD, faculty, and staff) and gender so that the proportion of respondents in each group reflects their proportion in the campus population.

Transportation-disadvantaged populations often face significant challenges in meeting their basic travel needs. Microtransit, a technology-enabled transit mobility solution, has the potential to address these issues by providing on-demand, affordable, and flexible services with multi-passenger vehicles. The ways in which microtransit supports underserved populations and the factors influencing its adoption are not well-studied, however. This research examines SmaRT Ride, a microtransit pilot program in the Sacramento, California, area operated by Sacramento Regional Transit. The project evaluates a broad range of factors influencing microtransit adoption and travel behavior among underserved populations using original revealed choice survey data collected from February – May 2024 with online and intercept surveys. A descriptive analysis revealed that SmaRT Ride has improved transportation access for these communities, complements the transit system by connecting fixed-route transit, and offers a cost-effective alternative to other transportation modes. A binary logistic regression was employed to explore differences between microtransit users and non-users with microtransit awareness. The results indicate that homeownership, employment status, frequency of public transit service use, and attitude towards transit significantly affect microtransit use. Homeowners are more likely to use microtransit, while households without employed members are less likely. In contrast, part-time employees show a higher inclination to use microtransit. Regular public transit users are also more likely to incorporate microtransit into their routines, with a positive attitude toward public transit further increasing the likelihood of its use. The nuanced understanding of microtransit adoption presented here can inform targeted strategies to promote its use among transportation-disadvantaged groups. The results suggest that integrating microtransit with existing transit, outreach programs, discounted or free access, extended service hours, and supporting homeownership and affordable housing in transit-rich areas can encourage microtransit adoption by low-income and/or underserved individuals.

View the NCST Project Webpage

Pilot programs in California and beyond are exploring universal basic mobility (UBM), which calls upon government actors to ensure that everyone can access transportation services for basic needs. UBM addresses the problem of transport poverty, which is defined in various ways but is generally when transportation spending puts one below the poverty line or transportation is exceedingly time-consuming, unsafe, or unavailable. This research evaluated UBM-inspired pilot programs in Oakland and Bakersfield, via pre- and post-pilot surveys and interviews during the programs.

Both pilots provided free-fare transportation services (shared micromobility in both cities and public transit services in Oakland) to populations vulnerable to transport poverty (residents of a low-income, minority-majority community in East Oakland and current and former foster youth in Bakersfield). Participants replaced car trips and/or walking with shared mobility and/or public transportation and reported improved access to jobs, food, health care, and social and recreational opportunities. They were able to go more places, more efficiently, and perhaps even enjoy the trip. The services helped participants carry out activities with more comfort and dignity and yielded social and cultural benefits. Lessons learned for program design and administration include the need for: providing some car-based services; clear communications throughout the program; training/support components for new mobility options; troubleshooting operations; and planning for turnover in program staff and fast changes in micromobility services.

This report summarizes the findings from ten sets of analyses that investigated ways the COVID-19 pandemic transformed people's activity-travel patterns. Data were collected through three waves of surveys in Spring 2020, Fall 2020, and Summer 2021 in California and the rest of the US. We found that there was a substantial shift among California workers from physical commuting to exclusive remote work in 2020, followed by a transition to hybrid working schedules by Summer 2021. The adoption of remote work and hybrid work varied significantly among population subgroups, with higher income, more educated individuals, and urban residents showing the greatest shift to these arrangements. In terms of mode use and vehicle ownership, increased concerns about the use of shared modes of travel correlated with an increasing desire to own a car. We observed a major decrease in walking for commuting purposes and a significant increase in walking and biking for non-work trips. The study also found a reduction in the demand for, and/or an elevated aversion to, ridehailing because of the shared nature of the service. Regarding shopping patterns, the study found a nearly five-fold increase in the number of respondents who shopped online at least once per week between Fall 2019 and Spring 2020. However, part of this increase vanished by Fall 2020. Overall, the pandemic brought both temporary changes and longer-term impacts. The study proposes strategies to promote sustainable transportation and social equity among different population groups as communities strive to recover from the pandemic.

The historical impacts of transportation planning and investment have left lasting scars on communities of color and low-income communities. This research evaluates online equity tools that exist as spatial dashboards —i.e., interactive maps in which the parameters of interaction are controlled. Twelve tools ranging from the national to the local level were identified and qualitatively assessed for their ability to address conditions related to transportation equity. The evaluation focused on how each tool defines disadvantaged communities, the outcomes they measure (benefits, burdens, or other), their ease of use, and their ability to guide decisions about equity. The findings show a diversity of methods and metrics in defining disadvantage, with most relying on composite demographic indexes and comparative population thresholds. Tools most commonly provided accessibility metrics to assess transportation benefits, while incorporating a range of environmental and health indicators as burden measures. A minority of tools had integrated features to support planning or project implementation. This study provides examples of promising practices in transportation equity support tools.

This study delves into the energy and emissions impacts of Shared Autonomous and Electric Vehicles (SAEVs) on disadvantaged communities in California. It explores the intersection of evolving transportation technologies—electric, autonomous, and shared mobility—and their implications for equity, energy consumption, and emissions. Through high-resolution spatial and temporalanalyses, this research evaluates the distribution of benefits and costs of SAEVs across diverse populations, incorporatingenvironmental justice principles. Our quantitative findings reveal that electrification of the vehicle fleet leads to a 63% to 71% decrease in CO2 emissions even with the current grid mix, and up to 84%-87% under a decarbonized grid with regular charging. The introduction of smart charging further enhances these benefits, resulting in a 93.5% - 95% reduction in CO2 emissions. However, the distribution of these air quality benefits is uneven, with disadvantaged communities experiencing approximately 15% less benefits compared to more advantaged areas. The study emphasizes the critical role of vehicle electrification and grid decarbonization in emissions reduction, and highlights the need for policies ensuring equitable distribution of SAEV benefits to promote sustainable and inclusive mobility.

View the NCST Project Webpage

Recent California regulatory efforts, United States goals, and industry roadmaps all target net-zero greenhouse gas (GHG) emissions from the cement and concrete industries within a few decades. While changes in production of cement and concrete, including varying constituents, can greatly reduce GHG emissions, carbon dioxide removal (CDR) will be needed to meet this net-zero goal. Hydrated cement in concrete can carbonate (i.e., form carbon-based minerals with atmospheric CO2) and thus act as a CDR mechanism. This process occurs faster with a large surface area, such as crushed concrete at its end-of-life (EoL), which can be uniquely leveraged by transportation infrastructure projects. In this work, a literature review of key parameters that can facilitate desired CO2 uptake for transportation projects at their end of life is conducted and an initial meta-analyses of data from the literature to inform CO2 uptake for individual projects is performed. Initial considerations for what concomitant impacts may arise from this process are presented. Finally, experiments to fill a key gap in understanding how thin crushed concrete must be spread to maximize uptake reactions are conducted. Cumulatively, findings will inform whether carbonation can be implementedin a way that would support policies that include carbonation as a route for reducing emissions from cement-based materials in transportation applications

View the NCST Project Webpage

While transportation infrastructure and efficiency should inform where to build more housing, little is known about how housing allocation and development processes can be coordinated more systematically with transportation. To date, transportation-housing coordination has often relied on the densification of areas near rail transit stations, putting heavy burdens on these locations and their residents. Much less attention has been paid to how densification can be achieved in a more equitable manner by encompassing other sites. This report directs attention to non-rail locations, specifically low vehicle miles traveled (VMT) areas and bus corridors, and examines the challenges that can arise in promoting densification more broadly. It shows that data uncertainties can make it challenging to identify low VMT locations and that prioritizing only low VMT locations for residential development may have limited effectiveness in expanding housing opportunities in high opportunity areas. The report further explores ways to achieve more inclusive densification of non-rail transit areas and highlights the importance of anti-displacement strategies.

Crash modification factor (CMF) is an effectiveness measure of safety countermeasures. It is widely used by state agencies to evaluate and prioritize various safety improvement projects. The Federal Highway Administration (FHWA) CMF Clearinghouse provides CMFs for a broad range of countermeasures, but still, the existing CMFs often cannot meet the needs for characterizing the safety impacts of countermeasures in new scenarios. Developing CMFs, meanwhile, is costly, time-consuming, and requires extensive data collection. A more cost-effective way to provide preliminary CMF estimations is needed. To address this need, this study develops a low-cost and easily extendable data-driven framework for CMF predictions. This framework performs data mining on existing CMF records in the FHWA CMF Clearinghouse. To tackle the heterogeneity of data, interdisciplinary techniques to maintain model compatibility were created and used. The project also integrates multiple machine-learning models to learn the complex hidden relationships between different safety countermeasure scenarios. Finally, the proposed framework is trained against the CMF Clearinghouse data and performs comprehensive evaluations. The results show that the proposed framework can provide CMF predictions for new countermeasure scenarios with reasonable accuracy, with overall mean absolute errors less than 0.2. We also discuss an enhanced approach that leverages structured information in certain CMF descriptions, which can boost the CMF prediction accuracy, showing a mean absolute error less than 0.1 in a case study.

To understand the extent to which micromobility services such as bike-share and scooter-share are enabling car-light lifestyles by replacing driving, we explore the trip-chaining patterns of micromobility users. We use travel diary data collected from micromobility users in 48 cities across the US. Our analysis incorporated 15,985 trip chains from 1,157 survey participants who provided at least seven days of travel diary data, and an imputed dataset of 35,623 trip chains from 1,838 participants from the same survey. Our analysis of both datasets shows that a considerable portion of car owners are leaving their cars at home when using micromobility. This suggests that, for a subset of users, micromobility can form part of a car-free or car-light day of travel, despite having a car available. Trip chains with less frequent car use are composed of a variety of different modes in combination with micromobility. Micromobility services are supportive of complex trip chains that include both work and non-work trips with reduced reliance on cars. The use of micromobility services tends to entirely replace shorter car trips on shorter-length trip chains. Our findings show the importance of considering the chain of trips rather than individual trips to understand the sustainability potential of micromobility services. The policy implications of these findings are improving methods of travel behavior analysis of shared mobility services.