Browsing by Author "Dunn, Naomi J."

Now showing 1 - 9 of 9
  • Thumbnail Image
    Applying the Crash Trifecta Approach to SHRP 2 Data
    Dunn, Naomi J.; Hickman, Jeffrey S.; Soccolich, Susan A.; Hanowski, Richard J. (National Surface Transportation Safety Center for Excellence, 2018-04-06)
    The crash trifecta model does not consider crash genesis as a simple unitary element, but rather as a convergence of three separate, converging elements: (1) unsafe pre-incident behavior or maneuver; (2) transient driver inattention; and (3) an unexpected traffic event. Previous results from Phase I of the Crash Trifecta study showed that the presence of all three crash trifecta elements increased as the severity of a safety-critical event (SCE) increased. Given the limited number of crashes available in Phase I, however, it was not possible to identify trends in the presence of specific crash trifecta elements or to break the data down by incident type or crash severity. The current study built on the methods and results from Phase I by applying the crash trifecta model to the Second Strategic Highway Research Program (SHRP 2) Naturalistic Driving Study (NDS), which greatly increased the number of SCEs available for analysis. The results of Phase II show that elements well within a driver’s control are at the core of the majority of SCEs. Unsafe driving behavior was the most prevalent crash trifecta element, occurring in 70% of crashes and 52% of near-crashes. Unsafe driving behavior combined with transient inattention contributed to over 25% of crashes and almost 33% of at-fault crashes in the current study, compared to 5% of near-crashes and 8% of at-fault near-crashes, indicating that a crash is much more likely to occur if the unsafe driver is also not paying attention. The prevalence of the remaining two crash trifecta elements (i.e., transient inattention and unexpected event) varied depending on the severity of the SCE. An unexpected event was more likely to be present in near-crashes (74%) compared to crashes (25%), while the opposite was true for transient inattention near-crashes (28%) and crashes (43%). The increased number of SCEs in Phase II compared Phase I meant that the data set could be broken down by incident type for a more in-depth assessment of the applicability of the crash trifecta model. Of the 16 different incident types, the most common crashes were animal related, rear end (striking), rear end (struck), and road departure (left or right). The most common near-crashes were animal related, rear end (striking), sideswipe (same direction), and turn into path (same direction). The majority of different types of near-crashes tended to be associated with pedestrians, animals, pedalcyclists, or other vehicles behaving unexpectedly. The presence of transient inattention in a number of incident types resulted in a higher proportion of crashes than near-crashes. As was the case in Phase I, the results of the current Phase II study suggest that assigning a single, unitary critical reason as the proximal cause of the SCE without considering additional contributing factors is likely to be a limitation that does not address the complexities involved in the genesis of a crash.
  • Thumbnail Image
    Commercial Motor Vehicle Driver Risk Based on Age and Driving Experience
    Dunn, Naomi J.; Soccolich, Susan A.; Hickman, Jeffrey S. (National Surface Transportation Safety Center for Excellence, 2020-04-17)
    The commercial motor vehicle (CMV) industry comprises a largely aging workforce, which adds to a widely held concern about a growing CMV driver shortage. As CMV drivers age and retire, there are fewer workers to step in and fill the gap. A possible solution to this problem is to recruit and hire younger drivers, although this poses a potential safety risk due to a lack of CMV driving experience among the younger driver population. However, it is largely unknown in the CMV industry what impact age has on driver risk independent of CMV driving experience, and vice versa. Thus, this study used data collected and compiled in a study sponsored by the Federal Motor Carrier Safety Administration (FMCSA), Commercial Driver Safety Risk Factors (Hickman et al., under Agency review), from more than 9,000 CMV drivers to determine the impact of age and CMV driving experience on crash rates, crash involvement, and moving violations. The results indicate that, while both age and CMV driving experience play a role in driver risk, CMV driving experience is more important than age when considering risk. This may be especially true for older inexperienced CMV drivers (e.g., over 55 years of age with less than 1 year of CMV driving experience), who had higher crash rates and odds of being involved in a crash than their younger, inexperienced counterparts. Generally speaking, the first year of driving a CMV is riskier in terms of crash rates, crash involvement, and moving violations, regardless of age. Thus, motor carriers may want to focus on driver training, including engaging older, experienced drivers in driver mentoring programs to share their knowledge with inexperienced CMV drivers. In addition, there are vehicle technologies that use dash cameras to help fleet managers improve driver safety, such as the Lytx DriveCam system. These cameras continually record video and provide evidence-based opportunities for driver training, which may provide additional benefits.
  • Thumbnail Image
    A Complex Driving Scenario for Describing Safety-Critical Event Causation
    Dunn, Naomi J.; Hickman, Jeffrey S.; Hanowski, Richard J. (2014-08-25)
  • Thumbnail Image
    Crash Trifecta: A Complex Driving Scenario Describing Crash Causation
    Dunn, Naomi J.; Hickman, Jeffrey S.; Hanowski, Richard J. (National Surface Transportation Safety Center for Excellence, 2014-07-28)
    When determining crash causation, crash databases emphasize a single, unitary critical reason (CR) as the primary proximal cause of a safety-critical event (SCE), which leaves no room for the specification of any other potential contributing factors to the crash/event genesis. This is despite the fact that it is well established in the transportation safety field that crash genesis typically involves a convergence of several factors. The aim of this study was to investigate the crash trifecta concept to determine if the convergence of multiple elements, rather than a single, unitary critical reason, has greater value in explaining the complexities of crash genesis. Specifically, the crash trifecta concept is defined as three separate, but converging, elements: 1. Unsafe pre-incident behavior or maneuver (e.g., speeding, tailgating, unsafe turn); 2. Transient driver inattention (which may be driving related, such as mirror use, or unrelated, such as reaching for an object); and 3. An unexpected traffic event (e.g., unexpected stopping by the vehicle ahead). The value of the crash trifecta concept and convergence concepts in crash causation is that these concepts provide a structure for understanding the complexities of crash genesis. Thus, the crash trifecta concept may help explain the differences between the genesis of a crash and lower-severity SCEs (e.g., near-crashes).
  • Thumbnail Image
    Driver Detention Times in Commercial Motor Vehicle Operations
    Dunn, Naomi J.; Hickman, Jeffrey S.; Soccolich, Susan A.; Hanowski, Richard J. (United States. Federal Motor Carrier Safety Administration. Office of Analysis, Research, and Technology, 2014-12)
    The purpose of this project was to quantitatively identify detention times in the commercial motor vehicle (CMV) industry. Although there is currently no standard definition, the industry commonly defines detention time as “any time drivers have to wait beyond 2 hours, which is the average time it takes to load or unload their cargo." Results indicated that drivers experienced detention time on approximately 1 in every 10 stops for an average duration of 1.4 hours. This represents the length of time the driver was detained beyond 2 hours; thus, he/she was loading/unloading at that delivery location for 3.4 hours in total. Medium-sized carriers (51-500 power units) had similar average detention times as large carriers (more than 500 power units); however, they experienced driver detention about twice as often as large carriers. For example, 19 percent of stops made by medium-sized carriers were accompanied by detention time compared to 9 percent of stops made by large carriers. The calculation of odds ratios (ORs) provided similar results for medium-sized carriers when compared to large carriers. The odds of a driver being detained were 2.17 times greater for medium-sized carriers than for large carriers. Operation type did not have much impact on the average length of detention time; however, operation type influenced how frequently drivers experienced detention time, with for-hire truck load (TL) carriers experiencing detention time more than twice as frequently as for-hire less-than-truckload (LTL) carriers and four times more often than private carriers. The OR analysis also indicated that for-hire TL carriers were worse off than for-hire LTL or private carriers. The odds of a driver being detained were nearly 5 times greater for for-hire TL carriers than for private carriers and 2.6 times greater than for for-hire LTL carriers. The odds of a driver being detained were 6.3 and 1.9 times greater for temperature controlled freight carriers than for dry bulk carriers, and liquid bulk/tank freight carriers, respectively.
  • Thumbnail Image
    Evaluating the Potential Safety Benefits of Electronic Hours-of-service Recorders Final Report
    Hickman, Jeffrey S.; Camden, Matthew C.; Guo, Feng; Dunn, Naomi J.; Hanowski, Richard J. (United States. Federal Motor Carrier Safety Administration. Office of Analysis, Research, and Technology, 2014-04)
    The purpose of the current study was to assess the benefits of installed electronic hours-of-service recorders (EHSRs) on safety and hours-of-service (HOS) violations related to Class 7 and 8 trucks as they operated during normal revenue service. Data were obtained through a third-party vendor that compiled previously-generated compliance data regarding participating motor carriers. Although the final data sets included data from 11 carriers representing small, medium, and large carriers (including a total of 82,943 crashes, 970 HOS violations, and 224,034 truck-years that drove a total of 15.6 billion miles), the data set in the current study was skewed toward larger, for-hire carriers and may not represent the overall U.S. trucking population. After controlling for calendar year, carriers in the data set, onboard safety system (OBSS) status, and long-haul/regional indicator, EHSR-equipped trucks had a significantly lower total crash rate (11.7 percent reduction) and a significantly lower preventable crash rate (5.1 percent reduction) than trucks not equipped with an EHSR. Small sample sizes limited the power to detect a significant difference between the EHSR cohort and the non-EHSR cohort for U.S. Department of Transportation (USDOT)-recordable and fatigue-related crashes. This result is primarily attributed to the lack of sufficient data (in terms of the number of these types of crashes) to be able to detect safety benefits with statistical significance at the observed level. After controlling for year, carrier index, OBSS status, and long-haul/regional indicator, EHSR-equipped trucks had a 53 percent lower driving-related HOS violation rate and a 49 percent lower non-driving-related HOS violation rate than trucks not equipped with EHSRs. The results show a clear safety benefit, in terms of crash and HOS violation reductions, for trucks equipped with EHSRs.
  • Thumbnail Image
    Guiding Driver Responses During Manual Takeovers from Automated Vehicles
    Greatbatch, Richard L.; Dunn, Naomi J.; Kim, Hyungil; Krasner, Alexander (Safe-D National UTC, 2023-11)
    The number of automated features in surface vehicles is increasing as new vehicles are released each year. Some features allow drivers to temporarily take their attention off the road to engage in other tasks. However, sometimes it is important for drivers to immediately take control of the vehicle. To take control safely, drivers must understand what is required of them and have the situation awareness (SA) to understand important changes or factors within the environment around them. To achieve this, drivers may be presented with necessary takeover information using a head-up display (HUD), which keeps the driver’s eyes on the road. This study investigated the impact of novel HUDs on driver SA during takeover on highways. Data collection included empirical data for takeover performance metrics, self-reported SA, and participant preferences. To investigate differences between conditions, statistical analyses utilized repeated measure analyses of variance (ANOVAs). The results indicated that HUDs can increase aspects of takeover performance on highways, with participants demonstrating lower response times and higher time-to-collision metrics. There was no significant impact of HUDs on driver SA. Results of this work identified potential use cases and design criteria for new designs of novel HUDs to deliver important information during takeover.
  • Thumbnail Image
    A Preliminary Investigation into the Safety-Critical Event Risk of Aging Commercial Motor Vehicle Drivers
    Dunn, Naomi J.; Antin, Jonathan F.; Soccolich, Susan A. (National Surface Transportation Safety Center for Excellence, 2018-09-07)
    The majority of research into age-related declines in driving performance has concentrated on light vehicle, non-commercial drivers. However, the aging of the commercial motor vehicle (CMV) workforce raises a number of important questions regarding the potential impact of age-related declines in perceptual, cognitive, and psychomotor performance on the ability to safely operate a CMV. The current study offers a secondary analysis of four existing naturalistic truck driving studies examining the safety-critical event risk of younger CMV drivers (30 to 40 years old) versus older drivers (50+ years old). Results for the initial analysis show that the younger and older driver groups did not differ significantly from each other, with the exception that the younger drivers had 2.4 times the odds of being involved in an at-fault near-crash. Additional comparisons were also conducted between younger drivers (30 to 40 years old), older drivers (50 to 64 years old), and the oldest drivers (65 years old or older), though the sample size of six drivers for the oldest drivers group was small. Results for the second analysis indicate that the SCE, at-fault SCE, near-crash, and crash-relevant conflict rates did not differ significantly between the younger, older, and oldest driver groups. Crash rates also did not differ significantly, though this needs to be interpreted with caution due to the small number of crashes in the final data set. In general, the results provide evidence that older (50 to 64 years old) drivers are as safe behind the wheel as their younger counterparts. Due to the small sample size for the oldest driver group (65+ years old), the preliminary impression that they are as safe as the other two groups cannot be statistically tested or confirmed.
  • Thumbnail Image
    Tips for Sharing the Road with Commercial Motor Vehicles: A Web-Based Approach
    Dunn, Naomi J.; Baker, Stephanie Ann; Blanco, Myra (National Surface Transportation Safety Center for Excellence, 2016-01-11)
    This report documents the Tips for Sharing the Road with Commercial Motor Vehicles website (http://www.cmvroadsharing.org). The website was created by the National Surface Transportation Safety Center for Excellence to educate teen drivers about how to share the road with heavy vehicles. The website incorporates video clips of real-world driving events captured during a naturalistic driving study conducted by the Virginia Tech Transportation Institute (VTTI). The video clips provide examples of both proper and improper driving behavior. The rationale for providing examples of both types of behavior was that effective education of drivers, especially those who are young and inexperienced, needs to show not only “what not to do,” but should also illustrate the alternative “correct” road sharing behavior. The naturalistic driving video clips shown on the website are all from the truck driver’s perspective to highlight the difficulties these drivers face on the road every day due to other drivers’ improper road sharing behavior.