Browsing by Author "Walker, Stuart"

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    Development of a Naturalistic Observer-Based Rating of Near-Crash Severity in Naturalistic Driving Data
    McClafferty, Julie A.; Walker, Stuart (National Surface Transportation Safety Center for Excellence, 2024-09-04)
    The analysis of safety-critical events, including crashes and near-crashes, from naturalistic driving studies has proven extraordinarily useful in guiding transportation safety policies, transportation technology, and transportation infrastructure. Near-crashes, which are much more common than crashes, have the potential to answer many research questions. However, they are difficult to define, and their severity is difficult to rate. By definition, there is no impact to measure in a near-crash and therefore no injury or property damage to assess. Near-crashes cover a range of scenarios, and perceptions of severity can vary greatly depending on the person experiencing or perceiving them. From a research perspective, this variability makes near-crashes challenging. Severe near-crashes may be considered most similar to crashes and serve as better surrogates than less severe near-crashes, but less severe near-crashes are still very different from “normal” driving and are still relevant to policy, technology, and infrastructure development research. In this effort, an observer-based, naturalistic near-crash severity rating protocol was developed and tested to help researchers produce near-crash event data effectively and reduce associated variability. Goals included producing a protocol that can (1) produce consistent and meaningful ratings, (2) be incorporated effectively and efficiently into the standard primary event assessment, (3) be implemented by trained data reductionists with access to video and basic kinematic data charts, (4) be applied without complex models, calculations, or statistical modeling, and (5) mirror the existing crash severity scale in implementation and conceptualization. A key concept in this work was that of conflict urgency. There is no clear answer about how urgency can or should be observed or measured in naturalistic data, especially in non-crash scenarios. It is clear, however, that the concepts of collision imminence (a sense of conflict timing) and potential crash severity (related to possible damage and injury) are important factors. Thus, an additional goal was to achieve a balance between actual kinematics, predictive outcomes, and perceived subjective risks. Operational definitions, associated research protocols, and reference guides were developed for four levels of near-crash severity ranging from Critical Severity to Lower Severity. These are documented in the appendices. At their core, the definitions are based on objective metrics such as relative speed, time-to-collision, and type of conflict, but with room for subjective assessments. An iterative approach was used in the development of these definitions, and this included assessments to evaluate interrater reliability. Results indicated that reference materials and training improve interrater reliability.
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    Making design work: Sustainability, Product Design and Social Equity
    Walker, Stuart; Dorsa, Edward A. (Kluwer, 2001)
    This paper discusses the relationship between the product designer, sustainability and the creation of good quality work within the manufacturing sector. When the principles of sustainability are applied to the nature of employment it points to a new direction for design and product production where ethics, environmental issues and social wellbeing become far more important criteria for ‘success’ than is currently the norm. Awareness of the relationship between ‘work’ and sustainability is not generally being addressed, but needs to become a part of a comprehensive approach to sustainability in design school curricula.
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    Streamlining Drowsiness Assessment: An In-Depth Review of ORD and PERCLOS Methods
    Soccolich, Susan A.; Hammond, Rebecca; Camden, Matthew C.; Walker, Stuart (National Surface Transportation Safety Center for Excellence, 2024-03-15)
    Every year, drowsy and fatigued driving contributes to thousands of crashes and their resulting injuries and fatalities. Naturalistic driving data allows researchers an opportunity to better understand drowsy driving through review of driver-facing video capturing the driver’s behavior and eyes. Two drowsiness measures that have been successfully used in naturalistic driving data are Observer Rating of Drowsiness (ORD) (Wiegand, McClafferty, McDonald, & Hanowski, 2009) and manual percentage of eye closure (PERCLOS) (Wierwille & Ellsworth, 1994). The current study explored how different drowsiness measures impact fatigue determination for an event and study estimates of fatigue prevalence, risk, and secondary task association for truck and motorcoach drivers. Analyses investigated PERCLOS scores using 1 minute of data (PERCLOS 1) versus 3 minutes of data (PERCLOS 3). The study found the sample size of events with PERCLOS data increased by 8.94% when PERCLOS 1 criteria were used. Overall, matching fatigue determination (whether fatigue was observed) in PERCLOS 3 and PERCLOS 1 scores was found for between 95.89% and 99.48% of truck and motorcoach baselines (BLs) and safety-critical events (SCEs). The risk of SCE involvement when driving while fatigued was consistent for truck drivers when using PERCLOS 1 or PERCLOS 3 to determine fatigue. However, for motorcoach drivers, the risk of SCE involvement when driving while fatigued depended on the PERCLOS measure used. The study also aimed to determine how to potentially lessen the effort of fatigue data reduction in future studies and obtain the most valuable dataset at the lowest cost to time and budget. The single fatigue reduction approach with the lowest time and cost budget was PERCLOS 1 for all events. However, a targeted fatigue reduction approach that includes ORD for all events and targeted PERCLOS 3 or PERCLOS 1 reduction for events that meet or exceed an ORD threshold can reduce the cost of fatigue reduction while maintaining the advantage of ORD reduction.