Browsing by Author "Liang, Dan"

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    Advanced Driver Assistance Systems and Older Drivers – Mobility, Perception, and Safety
    Liang, Dan (Virginia Tech, 2023-10-25)
    The aging process is often accompanied by declines in one or more physical, vision, and/or cognitive abilities that may impact driving safety. As older drivers become more self-aware of these functional deficits, they have the tendency to engage in self-regulation practices, such as less driving and avoiding challenging driving situations. This tendency may gradually evolve to give up driving altogether. Advanced Driver Assistance Systems (ADAS) holds promise for improving older drivers' safety on the road as well as maintaining their mobility by compensating for declines in visual, cognitive, and physical capabilities. However, the perception of these technologies can influence the realization of these expected benefits. The overarching goal of this research is to understand and enhance the safety and mobility of older adults by examining the impact of ADAS. The dissertation addresses this goal by investigating mobility, perception, safety measures, and safety. Study 1 employed structure equation modeling (SEM) on the data from the Second Strategic Highway Research Program (SHRP 2) on driving habits with respect to age, gender, living status, health, and functioning capabilities. The results illustrate that older drivers' health is a reliable predictor of driving exposure, and cognitive and physical declines are predictive of their intention to reduce exposure and actual driving in challenging situations. These findings highlight that the aging population requires support for their mobility and likely road safety given their age-related impairments. Study 2 employed structure topic modeling on a focus group of older adults driving vehicles equipped with ADAS for six weeks was conducted to reveal five key issues to older drivers (in the order of prevalence): (1) safety, (2) confidence concerning ADAS, (3) ADAS functionality, (4) user interface/usability, and (5) non-ADAS related features. The findings point to a need for holistic ADAS design that not only must consider safety concerns but also user interfaces accommodating older adults' preferences and limitations as well as in-depth training programs to operate ADAS given the technology limitations. Study 3 employed correlation analysis and logistic regression on SHRP 2 data to reveal that the longitudinal deceleration events at greater than 0.60g and lateral acceleration events at greater than 0.40g appear most associated with older adults' driving risk and are predictive of near future crash and near-crashes (CNCs) occurrence and high-risk older drivers with acceptable accuracy. These findings indicate that high g-force events can be used to assess risk for older drivers, and the selection of thresholds should consider the characteristics of drivers. Study 4 compared high g-force events between two naturalistic driving studies to reveal that drivers who drove vehicles equipped with ADAS had lower longitudinal declaration rates, indicating the benefits of ADAS presence on older drivers' safety. When lane keeping assist (LKA) was engaged, lower high longitudinal deceleration was observed than when LKA was not engaged, indicating that older drivers tended to apply less aggressive braking when using LKA. Over several weeks of exposure to vehicles with ADAS presence, older drivers showed decreasing longitudinal deceleration but increasing lateral acceleration events. In other words, the potential of ADAS for positive safety-related impacts exists but some refinement in the design to reduce lateral events might be necessary.
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    Examining Senior Drivers Adaptation to Mixed Level Automated Vehicles: A Naturalistic Study
    Liang, Dan; Antin, Jonathan F.; Lau, Nathan; Stulce, Kelly E.; Baker, Stephanie Ann; Wotring, Brian (SAFE-D: Safety Through Disruption National University Transportation Center, 2019-08)
    Advances in the development of advanced vehicle technologies (AVTs), such as blind spot alerts, lane keep assist,lane alert, and adaptive cruise control, can benefit senior drivers by reducing exposure to hazards andcompensating for diminished cognitive abilities sometimes seen in this population. However, the degree to whichsuch benefits can be realized in this vulnerable population depends largely on the degree to which senior driverswill accept, adopt, and adapt to these features. This study investigated how 18 seniors, aged 70–79, accepted,trusted, and used mixed-function AVTs when provided an AVT-equipped vehicle to drive as they desired for a 6-week period. Researchers assessed attitudes and the effect of exposure via before-and-after exposure surveys, briefweekly check-in surveys during the driving exposure period, and focus group sessions conducted after theconclusion of the driving exposure period. Analyses revealed that seniors prefer technologies that inform, such asblind spot alert, over those that assert independent control over the vehicle, such as lane keep assist. Increasedconfidence in and willingness to use AVTs correlated positively with exposure, with adequate time for orientationand appropriate user documentation emerging as key factors determining senior drivers’ acceptance.
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    Examining senior drivers' attitudes toward advanced driver assistance systems after naturalistic exposure
    Liang, Dan; Lau, Nathan; Baker, Stephanie Ann; Antin, Jonathan F. (Oxford University Press, 2020-01-01)
    Background and Objectives: The increasing number of senior drivers may introduce new road risks due to age-related declines in physical and cognitive abilities. Advanced driver assistance systems (ADAS) have been proposed as solutions to minimize age-related declines, thereby increasing both senior safety and mobility. This study examined factors that influence seniors' attitudes toward adopting ADAS after significant exposure to the technology in naturalistic settings. Research Design and Methods: This study recruited 18 senior drivers aged 70-79 to drive vehicles equipped with ADAS for 6 weeks in their own environments. Afterward, each participant was enrolled in 1 of the 3 focus group sessions to discuss their changes in attitude toward ADAS based on their driving experiences. We applied structural topic modeling (STM) on the focus group transcripts to reveal key topics deemed important to seniors. Results: STM revealed 5 topics of importance for seniors. In order of prevalence, these were (i) safety, (ii) confidence concerning ADAS, (iii) ADAS functionality, (iv) user interface/usability, and (v) non-ADAS-related features. Based on topics and associated keywords, seniors perceived safety improvement with ADAS but expressed concerns about its limitations in coping with adverse driving conditions. Experience and training were suggested for improving seniors' confidence in ADAS. Blind spot alert and adaptive cruise control received the most discussion regarding perceived safety and comfort. Discussion and Implications: This study indicated that promoting road safety for senior drivers through ADAS is feasible. Acceptance and appropriate use of ADAS may be supported through intuitive and senior-friendly user interfaces, in-depth training programs, and owner's manuals specifically designed and tested for senior drivers.
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    Examining senior drivers’ acceptance to advanced driver assistance systems
    Liang, Dan; Antin, Jonathan F.; Lau, Nathan (2019-09-10)
    Advanced driver assistance systems (ADAS) can help maintain seniors’ safety and mobility with their decline in cognitive and physical capabilities. An early step of investigating the adoption and merits of ADAS for senior drivers is examining the factors that influence senior drivers’ acceptance of the technology. This paper presents our modeling effort on the acceptance of 18 senior drivers towards adaptive cruise control (ACC) and lane control features after six weeks of naturalistic driving with study vehicles. Adapting the Technology Acceptance Model (TAM), our model is built on questionnaire data on perceived usefulness (PU), perceived ease of use (PEoU), usebased trust (T) and perceived satisfaction (PS) in predicting behavioral intention to use (BIU) ADAS. Two major findings in our modeling effort are that (i) perceived ease of use has significant influence on trust and (ii) perceived satisfaction has significant influence on behavioral intention to use.
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    Examining Seniors’ Adaptation to Mixed Function Automated Vehicles: Analysis of Naturalistic Driving Data
    Liang, Dan; Antin, Jonathan F.; Lau, Nathan; Stulce, Kelly E. (SAFE-D: Safety Through Disruption National University Transportation Center, 2021-02)
    The study examined whether advanced driver assistance systems (ADAS) can benefit the mobility and driving performance of senior drivers. Two groups of driving data, collected separately from two naturalistic driving projects, were examined. The Second Strategic Highway Research Program and the Examining Seniors’ Adaptation to Mixed Function Automated Vehicles project databases were used to compare measurements of mobility and driving performance. Mobility analyses did not yield significant differences between seniors who drove conventional vehicles and those who drove ADAS-equipped vehicles. As to driving performance, three analyses were conducted to address different research interests. Results indicated that ADAS-equipped vehicles influence seniors’ driving performance both in positive as well as negative ways. Seniors generally displayed better speed management performance while driving the ADAS-equipped vehicles. Using adaptive cruise control (ACC) may help seniors reduce the frequency and level of higher g-force accelerations. However, poorer lateral control performance was observed during trips where ACC was used. The study is the first to investigate the influence of ADAS on the mobility and driving performance of seniors in real-world traffic and road environments.
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    Modeling of older adults’ driving exposure and avoidance using objective driving data in a naturalistic driving study
    Liang, Dan; Lau, Nathan; Antin, Jonathan F. (Elsevier, 2022-09-01)
    Older adults in the United States rely heavily on driving their own vehicles to commute to work, shop for groceries, and access public services. To effectively help older adults maintain mobility and independence, we need to better understand how the cognitive, visual functioning, and health declines influence their tendency to self-restrict their driving. The objective of this study is to develop a causal model to examine the effects of age, gender, household status (specifically living alone), physical, cognitive, visual abilities, and health status on older adults’ driving mobility in terms of driving exposure and avoidance. Driving exposure was measured by actual driving data, whereas driving avoidance was assessed by both self-report data and actual driving exposure to challenging situations. Structural equation modeling was used to analyze data collected in the Second Strategic Highway Research Program Naturalistic Driving Study for establishing relationships between the selected factors and mobility. The structural equation model included a total of 794 participants aged 65 and over (367 or 46.22% females and 427 or 53.78% males). Results indicate that poorer health is associated with less driving exposure; deteriorating cognitive and physical capabilities are associated with more self-reported driving avoidance and less actual driving in challenging situations; visual function is associated with self-reported avoidance; living alone is associated with higher driving exposure in general as well as in challenging situations; self-reported driving avoidance of challenging situations has a negative association with actual driving in those same situations. The final model could be applied to predict older adults’ mobility changes according to their age, gender, household status, as well as their visual, physical, cognitive and health status.