research report

An Examination of the Impact That Electric Vehicle Incentives Have on Consumer Purchase Decisions Over Time

Abstract

The research team investigates the impacts of a combination of incentives on the purchase decisions of electric vehicle (EV) buyers in California from 2010 through 2017. The team employs a comprehensive survey of over 14,000 purchasers of EVs in California. The survey covers a range of purchase intentions, general demographics, and the importance of various incentives. The results indicate that the most important incentives for plug-in electric vehicle (PEV) owners are the federal tax credit, the state rebate, and HOV lane access. In addition, the importance of the incentives and their associated effect on purchase behavior has been changing over time: respondents are more likely to change their decisions and not buy a vehicle at all as time passes and the technology moves away from early adopters.

presentation

Asphalt Pavement Maintenance & Rehabilitation

policy brief

Electric Assisted Bikes (e-bikes) Show Promise in Getting People Out of Cars

Publication Date

April 1, 2019

Abstract

For over a decade, California has offered incentives towards the purchase of zero-emission vehicles as part of the state’s broader effort to reduce greenhouse gas emissions. Expanding California’s incentive program for zero-emission vehicles to include electric assisted bikes (e-bikes) has been a point of recent discussion. The following summarizes the existing evidence on the effects e-bicycling has on car travel, characteristics of e-bike incentive programs, and opportunities for increasing e-bicycling in California.

policy brief

Mobility Challenges Facing Older Adults: A Contra Costa County Case Study

Publication Date

April 1, 2019

Author(s)

David Ragland, Sarah Doggett, Tracy McMillan

Abstract

Meeting the mobility needs of an aging population is one of the most substantial challenges facing California in the coming decades. The number of residents age 60 and above will grow to 13.9 million by 2050, representing over 25% of the state’s population. Meanwhile, the number of residents age 85 and above is expected to increase by over 70% between 2010 and 2030. Many older adults, who have primarily been auto dependent, will reduce or stop driving due to medical and non-medical reasons. Declines in age-related physical functions may also reduce the ability to walk to access goods and services, and can make using public transportation more difficult. These reductions in mobility can have a negative impact on the physical and mental health of seniors.

research report

Evaluating the Impacts of Start-Up and Clearance Behaviors in a Signalized Network: A Network Fundamental Diagram Approach

Abstract

Numerical simulations have shown that the network fundamental diagram (NFD) of a signalized network is significantly affected by the green ratio. An analytical approximation of the NFD has been derived from the link transmission model. However, the consistency between these approaches has not been established, and the impacts of other factors are still unrevealed. This research evaluates the impacts of start-up and clearance behaviors in a signalized network from a network fundamental diagram approach. Microscopic simulations based on Newell’s car-following model are used for testing the bounded acceleration (start-up) and aggressiveness (clearance) effects on the shape of the NFD in a signalized ring road. This new approach is shown to be consistent with theoretical results from the link transmission model when the acceleration is unbounded and vehicles have the most aggressive clearance behaviors. This consistency validates both approaches, but the link transmission model cannot be easily extended to incorporate more realistic start-up or clearance behaviors. With the new approach, this project demonstrates that both bounded acceleration and different aggressiveness lead to distinct network capacities and fundamental diagrams. In particular, they lead to start-up and clearance lost times of several seconds; and these lost times are additive. Therefore, the important role that these behaviors play in the NFD shape is studied to reach a better understanding of how the NFD responds to changes. This will help with designing better start-up and clearance behaviors for connected and autonomous vehicles.

research report

Assessing and Addressing the Mobility Needs of an Aging Population

Publication Date

April 1, 2019

Author(s)

David Ragland, Grace Felschundneff, Kara MacLeod, Sarah Doggett, Tracy McMillan

Abstract

The mobility needs of an aging population is one of the most substantial challenges facing California in the coming decades. The number of residents aged 65 and older is expected to double between 2012 and 2050, and the number aged 85 and above is expected to increase by over 70% between 2010 and 2030. Declines in physical function related to age may reduce mobility options dramatically. A survey of 510 residents aged 55 and older in Contra Costa County was conducted to determine mobility patterns and limitations related to age and other factors. Results of the survey indicate that a majority of seniors are car-dependent. However, some older adults miss important activities due to mobility limitations associated with increasing age, poorer health, living alone, not having a licensed driver in the household, and having a disability. Mobility options are also limited in some geographic areas and demographic groups. Importantly, older adults want to “age in place.” Based on these findings and those in related studies, the travel options and the quality of life for older adults, now and in the future, can be greatly enhanced if efforts are made to develop mobility solutions beyond the use of private vehicles. The findings support the recommendations of recent regional plans such as the Coordinated Public Transit–Human Services Transportation Plan (2018), adopted by the Metropolitan Transportation Commission (MTC) of the San Francisco Bay Area, which recommends supporting a range of mobility options centered around shared mobility and accessibility for populations at risk for limited mobility.

published journal article

Use of Ride-Hailing Services among Older Adults in the United States

Abstract

This paper presents an analysis of data from the 2017 National Household Travel Survey to examine the factors influencing the adoption and the frequency of use of on-demand ride-hailing services such as Uber and Lyft among older adults. Using a zero-inflated negative binomial model (ZINB), the results indicate that the determinants of adoption of on-demand ride-hailing services (users versus non-users) are different from the determinants of the frequency of use of these services among older adult users. Seniors who are younger, living alone, in urban dwellings, more highly educated, more affluent, or male with a medical condition that results in asking others for rides are more likely to be adopters of ride-hailing services. However, seniors who are middle elderly, less educated, or are carless older adults, are more likely to be frequent users of on-demand ride-hailing services as long as they adopt these services. In addition, smartphone possession plays an important role in the adoption behavior of on-demand ride-hailing services among older adults. Results of bivariate analysis showed that older adult ride-hailing users make more transit trips than their non-user counterparts, suggesting that ride-hailing services have the potential to serve as a complementary form of public transportation for older adults. The findings of this research will help ride-hailing operators in identifying potential market segments of their services and in developing campaign strategies for potential adopters.

research report

Using GPS Tracking to Understand the Transportation Costs of Displacement: A San Francisco Pilot

Publication Date

March 1, 2019

Author(s)

Audrey Lieberworth, Karen Chapple, Miriam Zuk

Abstract

California’s housing crisis has spurred residential displacement of low-income households from its high-cost coastal regions. Yet little is known about the transportation costs of displacement. As low-income households are displaced from high to lower-cost areas that may lack high-quality transit options, one may expect them to shift transportation modes, have longer commutes, and pay more of their income for transportation. This study aimed to pilot several data collection instruments in an effort to design a larger study on the transportation costs of displacement. The team attempted to recruit people who were about to be evicted to download a GPS app on their phones and answer two surveys about their travel patterns and other characteristics before, during, and after their eviction. After seven months of active recruitment, and partnering with eviction defense organizations, the research team terminated the study without having collected any data. Ultimately the researchers believe a lighter touch study would have been more successful and that it may have been too much to ask a person undergoing what may be considered a traumatic life event to install a GPS tracking app on their phone and dedicate several hours and emotional energy to a study. The need to characterize the transportation costs of displacement, however, is still important and the research team believes a shorter retrospective survey may be a more appropriate data collection method to pilot.

research report

Arterial Traffic Estimation Using Field Detector and Signal Phasing Data

Publication Date

March 1, 2019

Author(s)

Abstract

In this project, a novel approach has been developed to estimate the traffic states on arterial road links controlled by signalized intersections using both loop detector data and signal phasing information. The research team derived a trapezoidal fundamental diagram that includes two occupancy thresholds to categorize the traffic states into three different regimes: uncongested, congested, and downstream queue spillback. The parameters used to compute these two thresholds are closely related to road geometry, detector layout, signal settings, and vehicle dynamics, which can be obtained from the field data.  A case study was performed using field data from three intersections along Huntington Drive in the City of Arcadia in the I-210 Connected Corridors pilot. Flow-occupancy relations were obtained for both advance and stop line detectors at the intersection approaches, and it was found that advance detector information is more reliable because it is less impacted by the traffic signal.  The proposed trapezoidal fundamental diagram was validated using a dataset with six months of detector data.

research report

Understanding the Impact of Local Policies and Initiatives on Plug-In Electric Vehicle Adoption - An In-Depth Study of the Sacramento Region

Abstract

The survey project described here is intended to be the beginning of a multi-year project on the effectiveness of various activities in growing consumer interest in purchasing Battery Electric Vehicles in the Sacramento region. This survey in Sacramento shows that engagement in plug-in electric vehicles (PEVs) is moderate, based on the following results: 50% of respondents had seen some PEV-related advertising, mostly on television or in print media; 47% were aware of the California Clean Vehicle Rebate, and 46% aware of the federal tax credit; 40% could correctly name a PHEV, and 50% a BEV; 25% had sought out information on PEVs, mostly through the internet or speaking to car salespeople, friends, or family. Compared to respondents to a 2014 state-wide survey, a higher percentage of respondents to this 2018 Sacramento survey had seen charging stations, and a similar percentage, 3.3%, had actively shopped for a BEV. Ordinal logistic regression modeling indicated that the following factors were associated with having considered purchasing a BEV: being enthusiastic about PEVs, knowing someone by name who owns a PEV, having sought out information on PEVs, knowing how to refuel a PEV, and being familiar with the vehicles. Considering a Battery Electric Vehicles purchase was not associated with having seen advertising, being aware of ride-and-drive events, having been in a PEV, having seen chargers, awareness of incentives, or the density of PEVs or charging stations near the respondent’s home. Results suggest that respondents who are interested in BEVs are a self-selecting group whose interest is not the result of promotional activities. Existing efforts to engage the general population have not yet had a significant impact on respondents thinking about purchasing a BEV. Future follow-up surveys will be able to track changes in respondent awareness, the impact of various advertising and awareness campaigns, and growing consumer engagement in PEVs over time.