Browsing by Author "Fang, Youjia"

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    Driver Coach Study: Using Real-time and Post Hoc Feedback to Improve Teen Driving Habits
    Klauer, Charlie; Ankem, Gayatri; Guo, Feng; Baynes, Peter; Fang, Youjia; Atkins, Whitney; Baker, Stephanie Ann; Duke, Rebekah; Hankey, Jonathan M.; Dingus, Thomas A. (National Surface Transportation Safety Center for Excellence, 2017-12-08)
    Novice teenage drivers have the highest rates of fatalities and injuries on U.S. roadways compared to any other age group. This experimental research was conducted to see if presenting novice teenage drivers and their parents with feedback on teen driving performance could decrease rates of crash/near-crash (CNC) involvement. Ninety-two newly licensed teens had their vehicles instrumented with a data acquisition system (the Virginia Tech Transportation Institute’s MiniDAS) and received driving feedback in the form of a light and a tone when a potentially risky behavior was detected. Behaviors, such as swerving, speeding, lane changing without a turn signal, hard braking, hard turning, and fast starts, were used to determine when feedback was administered. Feedback continued for six months and then was turned off for one month (in the seventh month) to determine if risky behaviors returned after feedback stopped. These data were compared to a separate study (the Supervised Practice Driving Study [SPDS]) of 90 teenage drivers in the same geographic location who did not receive feedback. Parental involvement was examined by tracking which teen/parent groups checked the website and which did not. Results suggest that real-time and post hoc feedback produce a relative reduction in the rate of CNC involvement, but only when the parent is logging in to the website. If parents do not log in to the website to review the coachable events, real-time and post hoc feedback do not improve CNC rates. The analyses also indicated that once feedback was turned off in Month 7, teen CNC rates returned to baseline levels, which suggests that 6 months of feedback is not enough time to instill safe driving habits in novice drivers. This result also suggests that parental involvement in driver education must continue through the independent driving phase to improve teen CNC rates. In general, these results support previous research on monitoring and feedback, which suggest that parental involvement is critical in improving teen driving safety. These results also support current Graduated Driver’s Licensing (GDL) policies and provide research-based evidence that these policies should be strengthened.
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    Evaluation of Older Driver Fitness-to-Drive Metrics and Driving Risk Using Naturalistic Driving Study Data
    Guo, Feng; Fang, Youjia; Antin, Jonathan F. (National Surface Transportation Safety Center for Excellence, 2015-07-28)
    In this study, we evaluated the relationship between older drivers’ fitness assessment profiles and their driving risk, represented primarily by crash and near-crash (CNC) rate, and secondarily by high g-force (HGF) event rate, all recorded during a naturalistic study of senior drivers. Due to the relatively small sample size in this pilot investigation (20 primary drivers), principal component analysis was used for dimension reduction and classification of the 60 total fitness profile metrics. Negative binomial regression models were employed to model the CNC and HGF events. The results indicated that contrast sensitivity measures were significantly associated with CNC rate. The greater the sensitivity, the lower the CNC rate, as would be the expected nature of that association. In the HGF event analysis, we found that CNC rate was positively related to HGF rate. The fitness metric contrast sensitivity was also related to HGF event rate. In addition, two metrics related to metacognition, a measurement of one’s perception of one’s own cognitive status, were associated with HGF event rate. Higher HGF rates were associated with greater self-rating of cognitive status as well as greater disparities between that same self-rating and an objective metric of cognitive status. The results of this study provide crucial information on the metrics and protocols which could be applied by motor vehicle departments, physicians, occupational therapists, Certified Driving Rehabilitation Specialists, and others for whom determining seniors’ fitness to drive is an important component of their work. Further, these results can be further investigated and validated using the much larger database of senior driver data collected in the Second Strategic Highway Research Program (SHRP 2) Naturalistic Driving Study.
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    Evaluation of the Interaction of Driver Behavior Based on SHRP 2 NDS Data
    Guo, Feng; Fang, Youjia (National Surface Transportation Safety Center for Excellence, 2024-07-25)
    Driver behavior constitutes a significant factor contributing to traffic crashes. This study examines the relationship between three primary categories of driver behavior—driver distraction, driving errors, and driver impairment—utilizing data from the Second Strategic Highway Research Program Naturalistic Driving Study. The findings offer concrete evidence of interactions among these behaviors, indicating that the presence of one behavior significantly influences the likelihood of another and the occurrence of two high-risk behaviors amplifies crash risk. This study underscores the multifaceted nature of driver behavior and its profound impact on road safety. The findings can provide crucial information for driver education programs, safety countermeasure development, and advanced driving assistance systems.
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    Modeling Driving Risk Using Naturalistic Driving Study Data
    Fang, Youjia (Virginia Tech, 2014-10-21)
    Motor vehicle crashes are one of the leading causes of death in the United States. Traffic safety research targets at understanding the cause of crash, preventing the crash, and mitigating crash severity. This dissertation focuses on the driver-related traffic safety issues, in particular, on developing and implementing contemporary statistical modeling techniques on driving risk research on Naturalistic Driving Study data. The dissertation includes 5 chapters. In Chapter 1, I introduced the backgrounds of traffic safety research and naturalistic driving study. In Chapter 2, the state-of-practice statistical methods were implemented on individual driver risk assessment using NDS data. The study showed that critical-incident events and driver demographic characteristics can serve as good predictors for identifying risky drivers. In Chapter 3, I developed and evaluated a novel Bayesian random exposure method for Poisson regression models to account for situations where the exposure information needs to be estimated. Simulation studies and real data analysis on Cellphone Pilot Analysis study data showed that, random exposure models have significantly better model fitting performances and higher parameter coverage probabilities as compared to traditional fixed exposure models. The advantage is more apparent when the values of Poisson regression coefficients are large. In Chapter 4, I performed comprehensive simulation-based performance analyses to investigate the type-I error, power and coverage probabilities on summary effect size in classical meta-analysis models. The results shed some light for reference on the prospective and retrospective performance analysis in meta-analysis research. In Chapter 5, I implemented classical- and Bayesian-approach multi-group hierarchical models on 100-Car data. Simulation-based retrospective performance analyses were used to investigate the powers and parameter coverage probabilities among different hierarchical models. The results showed that under fixed-effects model context, complex secondary tasks are associated with higher driving risk.
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    The Novel Role of Interleukin-1 Receptor-Associated Kinase 1 in the Signaling Process Controlling Innate Immunity and Inflammation
    Fang, Youjia (Virginia Tech, 2009-05-05)
    Obesity-induced chronic inflammation plays a key role in the pathogenesis of insulin resistance and the metabolic syndrome. Proinflammatory cytokines can cause insulin resistance in adipose tissue, skeletal muscle and liver by inhibiting insulin signaling transduction. Interleukin-1 receptor-associated kinase-1 (IRAK-1) is a serine/threonine kinase functioning in Toll-like Receptor signaling pathways, and plays an important role in inflammation and immune response. In our studies, we demonstrated that IRAK-1 is involved with the negative regulation of PI3K-Akt dependent signaling pathway induced by insulin and TLR 2&4 agonists. Out data also indicate that IRAK-1 can interact with IRS-1 protein both in vivo and in vitro. The binding sites for the IRAK1-IRS1 biochemical interaction are IRS-1's PH domain and IRAK-1's proline-rich LWPPPP motif. Our studies also indicate that IRAK-1 is involved with the negative regulation of glycogen synthesis through inhibiting PI3K-Akt signaling pathway and thus releasing GSK3β's inhibitory effect on glycogen synthase. Moreover, our studies also suggest that IRAK-1 is involved in the activation of transcription factors CREB and ATF-1 by stimulating CREB-Ser133 and ATF-1 phosphorylation. CREB transcription factor family induces genes involved in cellular metabolism, gene transcription, cell cycle regulation, cell survival, as well as growth factor and cytokine genes. That may partially explain our finding that IRAK-1 may be also involved with cell proliferation and survival pathway.