research report

Travel Behavior Changes Among Users of Partially Automated Vehicles

Abstract

Partially automated battery electric vehicles (BEVs) are being sold to and used by consumers. Estimates indicate that as of the end of 2019, there were over 700,000 Partially Automated Tesla Vehicles—the subject of this study—on the roads globally. Despite this, little research has been done to understand how they may be changing travel behavior. In this study, qualitative interviews with 36 users of Tesla battery electric vehicles with Autopilot were conducted. The goal of this was to understand how Autopilot is used, user experiences of the system, and whether the system has any impact on drivers’ travel behavior. The focus of the last of these aims was to determine whether Autopilot could cause or was causing an increase in vehicle miles traveled (VMT) among the study participants. Results from the interviews showed that partial automation leads to consumers traveling by car more and being more willing to drive in congested traffic. These changes are due to increased comfort, reduced stress, and increased relaxation due to the partial automation system, and because of the lower running costs of a BEV. The results also point to a need for further research of partially automated vehicles that are already on the market, as 11 of 17 reasons for increased vehicle miles traveled that have been identified in modeling studies of fully automated vehicles (not yet commercially available) applied to users of Autopilot.

research report

Transportation, Quality of Life, and Older Adults

Abstract

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, the research team 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, the team linked the HRS data to census-tract-level data from the US Census and a categorization of community types. The research team found that residential density and other features of urban built environments 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.

research report

Investigating the Influence of Dockless Electric Bike-share on Travel Behavior, Attitudes, Health, and Equity

Abstract

Cities throughout the world have implemented bike-share systems as a strategy for expanding mobility options. While these have attracted substantial ridership, little is known about their influence on travel behavior more broadly. The aim of this study was to examine how shared electric bikes (e-bikes) and e-scooters influence individual travel attitudes and behavior, and related outcomes of physical activity and transportation equity. The study involved a survey in the greater Sacramento area of 1959 households before (Spring 2016) and 988 after (Spring 2019) the Summer 2018 implementation of the e-bike and e-scooter service operated by Jump, Inc., as well as a direct survey of 703 e-bike users (in Fall 2018 & Spring 2019). Among household respondents, 3–13% reported having used the service. Of e-bike share trips, 35% substituted for car travel, 30% substituted for walking, and 5% were used to connect to transit. Before- and after-household surveys indicated a slight decrease in self-reported (not objectively measured) median vehicle miles traveled and slight positive shifts in attitudes towards bicycling. Service implementation was associated with minimal changes in health in terms of physical activity and number of collisions. The percentages of users by self-reported student status, race, and income suggest a fairly equitable service distribution by these parameters, but each survey under-represents racial minorities and people with low incomes. Therefore, the study is inconclusive about how this service impacts those most in need. Furthermore, aggregated socio-demographics of areas where trips started or ended did not correlate with and therefore are not reliable indicators of, the socio-demographics of e-bike-share users. Thus, targeted surveying of racial minorities and people with low incomes is needed to understand bike-share equity.

research report

The Opportunity Cost of Parking Requirements: Would Silicon Valley be Richer if its Parking Requirements were Lower?

Abstract

We estimated the off-street parking supply of the seven most economically productive cities in Santa Clara County, California, better known as Silicon Valley. Using assessor data, municipal zoning data, and visual inspection with aerial imagery, we estimated that about 14 percent of the land area in these cities is devoted to parking and that over half the average commercial parcel is parking spaces. This latter fact suggested that minimum parking requirements, if binding, could depress Silicon Valley’s commercial and industrial densities, and; thus, its productivity. In an exploratory empirical exercise, we simulated a reduction in parking requirements from the year 2000 forward and showed that under conservative assumptions, the region could have added space for an additional 12,886 jobs, which is 43 percent of the actual job growth that occurred during that time. These additional jobs would be disproportionately located in the region’s highest-wage zip codes, further implying a large productivity gain.

presentation

3 Revolutions Policy Webinar Series

presentation

Caltrans Planning Horizons Webinar

policy brief

General Plan Content Related to Transportation and Land Use Varies Significantly Across Cities in Orange County

Abstract

California cities and counties are required to prepare general plans, which serve as long-range planning documents for future growth. General plans do not necessarily focus on a specific investment project or regulatory action that shapes development patterns directly but rather play an important role in informing stakeholders (e.g., landowners, developers, planners, elected officials) and supporting their decision making. The state provides guidelines and requirements for general plans. However, the content and structure of general plans vary markedly across cities. Some cities simply list goals and policies, while other cities provide detailed information using various forms of written and visual presentation. An increasing number of studies have examined to what extent plans are implemented and under what circumstances they are implemented successfully. However, little is known about the informational content of general plans and how the structural characteristics of general plans can either facilitate or hinder the use of the plan itself.

research report

Improving the Distribution of Densities in Southern California

Abstract

Many of the biggest transportation challenges in Southern California arise not due to its overall density but due to the lack of concentration of densities. While recent years have witnessed increasing efforts to expand public transit services and encourage compact development in transit areas, there is a dearth of research providing support for improving the distribution of densities in the region. This project adopts a simultaneous equation modeling (SEM) approach to reveal the complexity of parcel-level (residential) land use intensification dynamics in a five-county Southern California metropolitan region with emphasis on the importance of reciprocal interactions between current and planned land use changes and the critical role of public transit accessibility. Results suggest that residential densification and upzoning processes reinforce each other. Urban residential upzoning can significantly promote the probability of parcel-level residential densification, even though it does not always lead to an immediate market response in every location. More importantly, the residential density increases are found to induce further plan/zoning modifications in nearby areas, indicating the presence of feedback loops in this dynamic relationship. There is also evidence of the positive influence of public transit accessibility. Single-family residential land parcels with greater access to high-quality transit services show a higher level of densification and upzoning probabilities when all other conditions are held constant. Such positive effects are detected not only in existing high-quality transit areas but also in locations where public transit services will be available in the future.

policy brief

Gaining Wait? Analyzing the Congestion Impacts of Road Diets in Los Angeles