National Highway Traffic Safety Administration

BACKGROUND: To understand the consequences of driving cessation in older adults, the authors evaluated depression in former drivers compared with active drivers. METHODS: Depression (as assessed using the Center for Epidemiological Studies Depression Scale), driving status, sociodemographic factors, health status, and cognitive function were evaluated for a cohort of 1953 residents of Sonoma County, California, aged 55 years and older, as part of a community-based study of aging and physical performance. The authors re-interviewed 1772 participants who were active drivers at baseline 3 years later. RESULTS: At baseline, former drivers reported higher levels of depression than did active drivers even after the authors controlled for age, sex, education, health, and marital status. In a longitudinal analysis, drivers who stopped driving during the 3-year interval (i.e., former drivers) reported higher levels of depressive symptoms than did those who remained active drivers, after the authors controlled for changes in health status and cognitive function. Increased depression for former drivers was substantially higher in men than in women. CONCLUSIONS: With increasing age, many older adults reduce and then stop driving. Increased depression may be among the consequences associated with driving reduction or cessation.

Rotational motion of the head as a mechanism for brain injury was proposed back in the 1940s. Since then a multitude of research studies by various institutions were conducted to confirm/reject this hypothesis. Most of the studies were conducted on animals and concluded that rotational kinematics experienced by the animal's head may cause axonal deformations large enough to induce their functional deficit. Other studies utilized physical and mathematical models of human and animal heads to derive brain injury criteria based on deformation/pressure histories computed from their models. This study differs from the previous research in the following ways: first, it uses two different detailed mathematical models of human head (SIMon and GHBMC), each validated against various human brain response datasets; then establishes physical (strain and stress based) injury criteria for various types of brain injury based on scaled animal injury data; and finally, uses Anthropomorphic Test Devices (ATDs) (Hybrid III 50th Male, Hybrid III 5th Female, THOR 50th Male, ES-2re, SID-IIs, WorldSID 50th Male, and WorldSID 5th Female) test data (NCAP, pendulum, and frontal offset tests) to establish a kinematically based brain injury criterion (BrIC) for all ATDs. Similar procedures were applied to college football data where thousands of head impacts were recorded using a six degrees of freedom (6 DOF) instrumented helmet system. Since animal injury data used in derivation of BrIC were predominantly for diffuse axonal injury (DAI) type, which is currently an AIS 4+ injury, cumulative strain damage measure (CSDM) and maximum principal strain (MPS) were used to derive risk curves for AIS 4+ anatomic brain injuries. The AIS 1+, 2+, 3+, and 5+ risk curves for CSDM and MPS were then computed using the ratios between corresponding risk curves for head injury criterion (HIC) at a 50% risk. The risk curves for BrIC were then obtained from CSDM and MPS risk curves using the linear relationship between CSDM - BrIC and MPS - BrIC respectively. AIS 3+, 4+ and 5+ field risk of anatomic brain injuries was also estimated using the National Automotive Sampling System - Crashworthiness Data System (NASS-CDS) database for crash conditions similar to the frontal NCAP and side impact conditions that the ATDs were tested in. This was done to assess the risk curve ratios derived from HIC risk curves. The results of the study indicated that: (1) the two available human head models - SIMon and GHBMC - were found to be highly correlated when CSDMs and max principal strains were compared; (2) BrIC correlates best to both - CSDM and MPS, and rotational velocity (not rotational acceleration) is the mechanism for brain injuries; and (3) the critical values for angular velocity are directionally dependent, and are independent of the ATD used for measuring them. The newly developed brain injury criterion is a complement to the existing HIC, which is based on translational accelerations. Together, the two criteria may be able to capture most brain injuries and skull fractures occurring in automotive or any other impact environment. One of the main limitations for any brain injury criterion, including BrIC, is the lack of human injury data to validate the criteria against, although some approximation for AIS 2+ injury is given based on the angular velocities calculated at 50% probability of concussion in college football players instrumented with 5 DOF helmet system. Despite the limitations, a new kinematic rotational brain injury criterion - BrIC - may offer a way to capture brain injuries in situations when using translational accelerations based HIC alone may not be sufficient.

An optimal preview control method is applied to the automobile path following problem. The technique is first used to examine the straight-line regulatory driving task and results compared with similar experimental measurements. The method is further demonstrated by closedloop simulation of an automobile driver/vehicle system during transient lane-change maneuvers. The computer simulation results are compared with equivalent vehicle test measurements.

The objective of this study was to investigate potential for traumatic brain injuries (TBI) using a newly developed, geometrically detailed, finite element head model (FEHM) within the concept of a simulated injury monitor (SIMon). The new FEHM is comprised of several parts: cerebrum, cerebellum, falx, tentorium, combined pia-arachnoid complex (PAC) with cerebro-spinal fluid (CSF), ventricles, brainstem, and parasagittal blood vessels. The model's topology was derived from human computer tomography (CT) scans and then uniformly scaled such that the mass of the brain represents the mass of a 50th percentile male's brain (1.5 kg) with the total head mass of 4.5 kg. The topology of the model was then compared to the preliminary data on the average topology derived from Procrustes shape analysis of 59 individuals. Material properties of the various parts were assigned based on the latest experimental data. After rigorous validation of the model using neutral density targets (NDT) and pressure data, the stability of FEHM was tested by loading it simultaneously with translational (up to 400 g) combined with rotational (up to 24,000 rad/s2) acceleration pulses in both sagittal and coronal planes. Injury criteria were established in the manner shown in Takhounts et al. (2003a). After thorough validation and injury criteria establishment (cumulative strain damage measure--CSDM for diffuse axonal injuries (DAI), relative motion damage measure--RMDM for acute subdural hematoma (ASDH), and dilatational damage measure--DDM for contusions and focal lesions), the model was used in investigation of mild TBI cases in living humans based on a set of head impact data taken from American football players at the collegiate level. It was found that CSDM and especially RMDM correlated well with angular acceleration and angular velocity. DDM was close to zero for most impacts due to their mild severity implying that cavitational pressure anywhere in the brain was not reached. Maximum principal strain was found to correlate well with RMDM and angular head kinematic measures. Maximum principal stress didn't correlate with any kinematic measure or injury metric. The model was then used in the investigation of brain injury potential in NHTSA conducted side impact tests. It was also used in parametric investigations of various "what if" scenarios, such as side versus frontal impact, to establish a potential link between head kinematics and injury outcomes. The new SIMon FEHM offers an advantage over the previous version because it is geometrically more representative of the human head. This advantage, however, is made possible at the expense of additional computational time.

The SIMon (Simulated Injury Monitor) software package is being developed to advance the interpretation of injury mechanisms based on kinematic and kinetic data measured in the advanced anthropomorphic test dummy (AATD) and applying the measured dummy response to the human mathematical models imbedded in SIMon. The human finite element head model (FEHM) within the SIMon environment is presented in this paper. Three-dimensional head kinematic data in the form of either a nine accelerometer array or three linear CG head accelerations combined with three angular velocities serves as an input to the model. Three injury metrics are calculated: Cumulative strain damage measure (CSDM) - a correlate for diffuse axonal injury (DAI); Dilatational damage measure (DDM) - to estimate the potential for contusions; and Relative motion damage measure (RMDM) - a correlate for acute subdural hematoma (ASDH). During the development, the SIMon FEHM was tuned using cadaveric neutral density targets (NDT) data and further validated against the other available cadaveric NDT data and animal brain injury experiments. The hourglass control methods, integration schemes, mesh density, and contact stiffness penalty coefficient were parametrically altered to investigate their effect on the model's response. A set of numerical and physical parameters was established that allowed a satisfactory prediction of the motion of the brain with respect to the skull, when compared with the NDT data, and a proper separation of injury/no injury cases, when compared with the brain injury data. Critical limits for each brain injury metric were also established. Finally, the SIMon FEHM performance was compared against HIC15 through the use of NHTSA frontal and side impact crash test data. It was found that the injury metrics in the current SIMon model predicted injury in all cases where HIC15 was greater than 700 and several cases from the side impact test data where HIC15 was relatively small. Side impact was found to be potentially more injurious to the human brain than frontal impact due to the more severe rotational kinematics.

<div class="htmlview paragraph">Since 1976, the National Highway Traffic Safety Administration (NHTSA) has pursued biomechanical research concerning lateral impacts to automotive occupants. These efforts have included (a) the generation of an experimental data base containing both detailed engineering and physiological responses of human surrogates experiencing lateral impacts, (b) the analysis of this data base to develop both an injury index linking the engineering parameters to an injury severity level and response corridors to guide in the design of a test dummy, and (c) the development and refinement of a side impact test dummy suitable for use in safety systems development and evaluation. The progress of these efforts has been periodically reported in the literature [<span class="xref">1</span>-<span class="xref">17</span>]<span class="xref">*</span> and these references document the evolutionary trail NHTSA has followed over the duration of this research program.</div> <div class="htmlview paragraph">The purpose of this paper is to state NHTSA's current understanding of the side impact phenomena by summarizing the currently available biomechanical data, explaining the process by which current injury index and mechanical response corridors were developed, and detailing the current status of NHTSA's Side Impact Dummy (SID).</div>

Despite an abundant use of the term “Out of the loop” (OOTL) in the context of automated driving and human factors research, there is currently a lack of consensus on its precise definition, how it can be measured, and the practical implications of being in or out of the loop during automated driving. The main objective of this paper is to consider the above issues, with the goal of achieving a shared understanding of the OOTL concept between academics and practitioners. To this end, the paper reviews existing definitions of OOTL and outlines a set of concepts, which, based on the human factors and driver behaviour literature, could serve as the basis for a commonly-agreed definition. Following a series of working group meetings between representatives from academia, research institutions and industrial partners across Europe, North America, and Japan, we suggest a precise definition of being in, out, and on the loop in the driving context. These definitions are linked directly to whether or not the driver is in physical control of the vehicle, and also the degree of situation monitoring required and afforded by the driver. A consideration of how this definition can be operationalized and measured in empirical studies is then provided, and the paper concludes with a short overview of the implications of this definition for the development of automated driving functions.

This report describes the development of an evidence-based guideline for external hemorrhage control in the prehospital setting. This project included a systematic review of the literature regarding the use of tourniquets and hemostatic agents for management of life-threatening extremity and junctional hemorrhage. Using the GRADE methodology to define the key clinical questions, an expert panel then reviewed the results of the literature review, established the quality of the evidence and made recommendations for EMS care. A clinical care guideline is proposed for adoption by EMS systems. Key words: tourniquet; hemostatic agents; external hemorrhage.

Mind wandering is a pervasive threat to transportation safety, potentially accounting for a substantial number of crashes and fatalities. In the current study, mind wandering was induced through completion of the same task for 5 days, consisting of a 20-min monotonous freeway-driving scenario, a cognitive depletion task, and a repetition of the 20-min driving scenario driven in the reverse direction. Participants were periodically probed with auditory tones to self-report whether they were mind wandering or focused on the driving task. Self-reported mind wandering frequency was high, and did not statistically change over days of participation. For measures of driving performance, participant labeled periods of mind wandering were associated with reduced speed and reduced lane variability, in comparison to periods of on task performance. For measures of electrophysiology, periods of mind wandering were associated with increased power in the alpha band of the electroencephalogram (EEG), as well as a reduction in the magnitude of the P3a component of the event related potential (ERP) in response to the auditory probe. Results support that mind wandering has an impact on driving performance and the associated change in driver's attentional state is detectable in underlying brain physiology. Further, results suggest that detecting the internal cognitive state of humans is possible in a continuous task such as automobile driving. Identifying periods of likely mind wandering could serve as a useful research tool for assessment of driver attention, and could potentially lead to future in-vehicle safety countermeasures.

We examined the effects of trait driving anger, aggressive stimuli, and anonymity on aggressive driving behavior in a driving simulation task. High and low driving anger participants were randomly assigned to one of four conditions: (a) anonymous vs. identifiable driver; and (b) exposure to aggressive stimuli versus nonaggressive stimuli. Participants drove more aggressively when they were anonymous (d = .28) and exposed to aggressive stimuli (d = .05). Males drove more aggressively than did females (d = .06). No main or interaction effects were found for trait driving anger. Results suggest that situational factors affecting other forms of aggression are also important in aggressive driving.

A series of experiments was conducted on the Iowa Driving Simulator to examine driver reaction and performance in an intersection incursion crash scenario. To validate these simulator trials, a second study was run on a test track using a similar intersection incursion scenario to examine driver reaction and vehicle performance. Results showed that there was statistical equivalence between important driver reaction times with both studies.

A technique for synthesizing closed-loop control of linear time-invariant systems during tracking of previewed inputs is presented. The derived control is directly dependent upon the properties of the controlled system and is obtained by minimization of a defined previewed output error.

The goal of sobriety checkpoints is to deter drinking and driving by systematically stopping drivers for assessment of alcohol impairment, thus increasing the perceived risk of arrest for alcohol-impaired driving. This review examines the effectiveness of random breath testing (RBT) checkpoints, at which all drivers stopped are given breath tests for blood alcohol levels, and selective breath testing (SBT) checkpoints, at which police must have reason to suspect the driver has been drinking before demanding a breath test. A systematic review of the effectiveness of sobriety checkpoints in reducing alcohol-involved crashes and associated injuries and fatalities was conducted using the methodology developed for the Guide to Community Preventive Services (Community Guide) . Substantial reductions in crashes were observed for both checkpoint types across various outcome measures and time periods. Results suggest that both RBT and SBT checkpoints can play an important role in preventing alcohol-related crashes and associated injuries.

The absence of emergency medical services (EMS) patient care data has hindered development and evaluation of EMS systems. The National Highway Traffic Safety Administration (NHTSA), in cooperation with the Health Resources and Services Administration (HRSA), has provided funding to the National Association of State EMS Directors to develop a National EMS Information System (NEMSIS). NEMSIS is being designed to provide a uniform national EMS dataset, with standard terms, definitions, and values, as well as a national EMS database, with aggregated data from all states on a limited number of data elements. Forty-eight of the states, the District of Columbia, and three territories signed a memorandum of agreement documenting support for the NEMSIS project and expressing a desire for full implementation of the NEMSIS dataset. NHTSA has agreed to house the National EMS Database at its National Center for Statistics and Analysis. NHTSA, in cooperation with HRSA and the Centers for Disease Control and Prevention, recently entered into a cooperative agreement with the University of Utah School of Medicine to operate a NEMSIS Technical Assistance Center that will provide related assistance to official EMS agencies and to commercial software vendors. The Technical Assistance Center will also biannually assess state and territorial capabilities to provide data to the national EMS database. NEMSIS will provide a uniform national EMS dataset, with standard terms, definitions, and values, as well as a national EMS database, with aggregated data from all states on a limited number of data elements. Many of the potential benefits of implementation of NEMSIS are enumerated in this report.

The present study investigated the effects of discomfort glare on driving behavior. Participants (old and young; U. S. and Europeans) were exposed to a simulated low-beam light source mounted on the hood of an instrumented vehicle. Participants drove at night in actual traffic along a track consisting of urban, rural, and highway stretches. The results show that the relatively low glare source caused a significant drop in detecting simulated pedestrians along the roadside and made participants drive significantly slower on dark and winding roads. Older participants showed the largest drop in pedestrian detection performance and reduced their driving speed the most. The results indicate that the deBoer rating scale, the most commonly used rating scale for discomfort glare, is practically useless as a predictor of driving performance. Furthermore, the maximum U. S. headlamp intensity (1,380 cd per headlamp) appears to be an acceptable upper limit.

<div class="htmlview paragraph">Finite element modelling has been used to study the evolution of strain in a model of the human brain under impulsive acceleration loadings. A cumulative damage measure, based on the calculation of the volume fraction of the brain that has experienced a specific level of stretch, is used as a possible predictor for deformation-related brain injury. The measure is based on the maximum principal strain calculated from an objective strain tensor that is obtained by integration of the rate of deformation gradient with appropriate accounting for large rotations. This measure is used here to evaluate the relative effects of rotational and translational accelerations, in both the sagittal and coronal planes, on the development of strain damage in the brain. A new technique for the computational treatment of the brain-dura interface is suggested and used to alleviate the difficulties in the explicit representation of the cerebrospinal fluid layer existing between the two solid materials.</div>

An analysis of the National Automotive Sampling System/Crashworthiness Data System (NASS/CDS) for the years 1993-1999 was conducted to determine the risk of injury to different body regions in frontal crashes. Lower extremities were the leading injured body region. The risk of lower limb injuries was significant in all crash modes. A detailed examination of these lower extremity injuries was then conducted using the AIS-90 injury codes. The long term consequence of lower extremity injuries was estimated using the Functional Capacity Index (FCI) associated with each AIS-90 injury code. The effect of a particular injury on society was reported in terms of total Functional Life-years Lost to Injury (LLI) which is defined as the product of FCI and the injured person's life expectancy. Using existing biomechanical data on lower extremity injuries, injury criteria and associated injury risk curves were synthesized for different regions of the lower extremity, namely 1) knee-thigh-hip complex fractures, 2) knee ligaments tears, 3) tibial plateau/condyle fractures, 4) tibia/fibula shaft fractures, 5) calcaneus, ankle, and midfoot fractures, 6) malleolar, ligament, and ankle injuries. The threshold for a 25% probability of injury for the 50th percentile male were then scaled to obtain the corresponding threshold for other adult sizes.

OBJECTIVES: Knowledge of how different indicators of drowsiness affect crash risk might be useful to drivers. This study sought to estimate how drowsiness related factors, and factors that might counteract drowsiness, are related to the risk of a crash. METHODS: Drivers on major highways in a rural Washington county were studied using a matched case-control design. Control (n=199) drivers were matched to drivers in crashes (n=200) on driving location, travel direction, hour, and day of the week. RESULTS: Crash risk was greater among drivers who felt they were falling asleep (adjusted relative risk (aRR) 14.2, 95% confidence interval (CI) 1.4 to 147) and those who drove longer distances (aRR 2.2 for each additional 100 miles, 95% CI 1.4 to 3.3). Risk was also greater among drivers who had slept nine or fewer hours in the previous 48 hours, compared with those who had slept 12 hours. Crash risk was less for drivers who used a highway rest stop (aRR 0.5, 95% CI 0.3 to 1.0), drank coffee within the last two hours (aRR 0.5, 95% CI 0.3 to 0.9), or played a radio while driving (aRR 0.6, 95% CI .4 to 1.0). CONCLUSION: Drivers may be able to decrease their risk of crashing if they: (1) stop driving if they feel they are falling asleep; (2) use highway rest stops; (3) drink coffee; (4) turn on a radio; (5) get at least nine hours sleep in the 48 hours before a trip; and (6) avoid driving long distances by sharing the driving or interrupting the trip.

This study evaluated the response of restrained post-mortem human subjects (PMHS) in 40 km/h frontal sled tests. Eight male PMHS were restrained on a rigid planar seat by a custom 3-point shoulder and lap belt. A video motion tracking system measured three-dimensional trajectories of multiple skeletal sites on the torso allowing quantification of ribcage deformation. Anterior and superior displacement of the lower ribcage may have contributed to sternal fractures occurring early in the event, at displacement levels below those typically considered injurious, suggesting that fracture risk is not fully described by traditional definitions of chest deformation. The methodology presented here produced novel kinematic data that will be useful in developing biofidelic human models. Additional analysis of the data produced by the reported tests as well as additional tests with a variety of loading conditions are required to fully characterize torso response including ribcage fracture tolerance.

OBJECTIVE: This paper describes the development of the Functional Capacity Index (FCI) and compares it to the Abbreviated Injury Scale (AIS) and the Injury Impairment Scale (IIS). METHODS: The FCI maps 1990 AIS injury descriptions into scores that reflect expected levels of reduced functional capacity at 1 year after injury. Its development involved three steps. First, an expert clinical panel identified 10 relevant dimensions of function and defined levels of capacity within each dimension. A group of 114 individuals then rated the relative severity of different levels of function in terms of their impact on daily living. The third step involved clinical experts assigning FCI scores to AIS '90 injury descriptions based on their knowledge of the likely 1-year consequences associated with each injury. As a first step in validating the FCI, 1 year postinjury levels of impairment (based on range of motion and strength) were correlated with FCI, IIS, and AIS scores derived for 301 patients with severe lower extremity fractures. RESULTS: Consistency of FCI scores derived within and across dimensions of function argue for the conceptual integrity of the index. Non-zero FCI scores were assigned to only 26% of the 1,272 AIS injury descriptions, indicating that, for most of the injuries in the AIS dictionary, very little or no residual impairment is expected for the average person at 1 year. FCI scores derived for 301 patients with lower extremity fractures ranged from 0 to 63 (out of a possible 100 points). A modest correlation was found between FCI scores and actual levels of impairment observed at 1 year. Compared with the AIS and the IIS, the FCI appeared to discriminate somewhat better among different levels of function. CONCLUSIONS: Although further empirical validation of the FCI is essential before it can be broadly applied, its development represents an important first step in the generation of an AIS-based measure of expected functional outcome. Its validation is encouraged across a variety of settings and injury types.