Optimal design alternatives of advance guide signs of closely spaced exit ramps on urban expressways

Advance guide signs for exit ramps along urban expressways are increasingly critical, enhancing safety and mobility by improving the flow of vehicles exiting urban expressways. However, research has devoted scant attention to advance guide signs for exit ramps. This study aimed to identify and propose optimal design alternatives for exit ramp advance guide signs for different types of exit spacing. This study conducted a driving simulation experiment consisting of five design alternatives of advance guide signs and two exit ramp spacing variation. Eight indicators were measured. The repeated-measure analysis of variances (ANOVA) and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) were performed for the influence analysis and efficiency evaluation of different schemes. Influence analysis results showed better design alternatives in five schemes of advance guide signs, enabling drivers to more easily locate destination exits and change lanes fewer times, in addition to reducing drivers' need to decelerate, and improving traffic flow in the key influence range of destination exit ramps. The percentage of drivers successfully locating the destination exits also increased with optimal design alternatives of advance guide signs. When the exit ramp spacing tightened, on the other hand, drivers had to make more lane changes and accelerate and decelerate more frequently in the key influence range. As a result, a lower percentage of drivers successfully located destination exits. Efficiency evaluation results were also obtained. In tight spacing, three advance guide signs are recommended to be placed at 1 km, 0.5 km and 0 km prior to the beginning of the tapered deceleration lane. If conditions are limited, at least two advance guide signs should be used. With greater spacing, four advance guide signs are recommended, located at 2 km, 1 km, 0.5 km, and 0 km prior to the beginning of the tapered deceleration lane. If road conditions are limited, three advance guide signs should be used.

Determination of critical time points in non-collision incidents of elderly passengers in standing position on urban bus

Objective: Due to the reduced physical ability of elderly, the occurrence of non-collision incidents is higher for these passengers in standing position. Therefore, the purpose of the present study is to determine the critical time points of non-collision incidents using the level of leg muscle activity in elderly standing passengers on urban bus.Methods: To determine the critical time points in the occurrence of non-collision incidents, the level of muscular activity of the standing passengers was analyzed using a surface electromyography (surface EMG) device during the movement scenario of the bus. The results of assessing the leg muscle activity was analyzed in SPSS software.Results: The contraction pattern of the leg muscles in standing passengers was consistent with Newton's First Law. The results showed that the level of muscular activity decreased in the right leg muscles when changing the phase of bus motion from acceleration to constant velocity. This level of muscular activity in the left leg muscles increased when constant velocity changed to deceleration. These changes were quite significant in the medial gastrocnemius and soleus muscles (P < 0.05).Conclusions: According to these findings, it was found that the acceleration and deceleration phases, especially the starting and changing phases of bus motion, are the most critical time points in the occurrence of non-collision incidents in elderly standing passengers on urban bus.

A numerical investigation of factors affecting lumbar spine injuries in frontal crashes

Recent field data analyses have shown that lumbar spine fractures occurred more frequently in late model vehicles than the early ones in frontal crashes. Therefore, the objective of this study was to investigate risk factors associated with lumbar spine fractures in frontal crashes. Parametric simulations were conducted using a set of validated vehicle driver compartment model, restraint system model, and a HIII mid-size male crash test dummy model. Risk factors considered in the study included occupant seating posture, crash pulse, vehicle pitch angle, seat design, anchor pre-tensioner, dynamic locking tongue, and shoulder belt load limiter. ANOVA and ANCOVA were used to test the statistical significance (p < 0.05). Simulation results showed that all the factors that reduced the risk of submarining increased the lumbar spine forces, indicating a direct conflict between submarining and lumbar spine fractures. Among all the factors selected, seat structure is the most significant factor in determining the lumbar spine force (p < 0.001). Crash pulse severity, time at which the peak crash deceleration reached, and pitch angle are also crucial for lumbar spine force. Specifically, increase in vehicle pitch angle increased lumbar spine force, but reduced injury measures to other body regions; while a crash pulse with early peak produced greater lumbar spine force than that with a late peak. On average, more reclined posture increased the lumbar spine force compared to upright posture, and decreases in the coefficient of friction between the pelvis and the seat cushion reduced the lumbar spine force. However, they are not statistically significant. This study provided better understanding of effects from design countermeasures to reduce occupant lumbar spine injuries in new generation of vehicle models.

Relationship between hazard-perception-test scores and proportion of hard-braking events during on-road driving - An investigation using a range of thresholds for hard-braking

Drivers with higher proportion of hard braking events have greater potential to be involved in an accident. In this study, we tested if hard braking events might be accounted for by drivers' hazard perception (HP) ability. Our investigation was based on an original approach. Usually, researchers define hard braking according to a single deceleration threshold (e.g., g<-0.5). In this study, we chose different thresholds for hard braking (-0.25 to -0.6 g) and for each threshold, we examined the linkage between HP test (HPT) scores and the proportion of hard braking events. We hypothesized that this linkage would be stronger if the threshold that defines hard braking is higher. This is because the stronger the braking events, the higher the likelihood that they resulted from later detection of hazards and the lower the likelihood that they resulted from other causes (e.g., road humps). Thirty-three drivers completed an HPT and used a smartphone app that recorded their vehicle kinematics. We estimated the coefficient of HPT score in a series of binomial regression models on the proportion of hard braking events. In accordance with our hypothesis, we found that the coefficient of HPT score changed as a function of the threshold for hard braking. This finding was based on a significant negative Spearman correlation between the coefficients and the threshold and on linear functions that we derived from two binomial models that allowed the coefficient of HPT to vary according to the threshold. Our findings show that hard braking events are related to HP ability and can inform safety interventions in response to excessive proportion of hard braking events. In addition, they demonstrate that using a range of thresholds for hard braking is a practical tool in the study of hard braking events. From a theoretical perspective, our findings provide strong support to hazard perception theory.

Exploring microscopic driving volatility in naturalistic driving environment prior to involvement in safety critical events-Concept of event-based driving volatility

The sequence of instantaneous driving decisions and its variations, known as driving volatility, prior to involvement in safety critical events can be a leading indicator of safety. This study focuses on the component of "driving volatility matrix" related to specific normal and safety-critical events, named "event-based volatility." The research issue is characterizing volatility in instantaneous driving decisions in the longitudinal and lateral directions, and how it varies across drivers involved in normal driving, crash, and/or near-crash events. To explore the issue, a rigorous quasi-experimental study design is adopted to help compare driving behaviors in normal vs unsafe outcomes. Using a unique real-world naturalistic driving database from the 2^nd Strategic Highway Research Program (SHRP), a test set of 9593 driving events featuring 2.2 million temporal samples of real-world driving are analyzed. This study features a plethora of kinematic sensors, video, and radar spatiotemporal data about vehicle movement and therefore offers the opportunity to initiate such exploration. By using information related to longitudinal and lateral accelerations and vehicular jerk, 24 different aggregate and segmented measures of driving volatility are proposed that captures variations in extreme instantaneous driving decisions. In doing so, careful attention is given to the issue of intentional vs. unintentional volatility. The volatility indices, as leading indicators of near-crash and crash events, are then linked with safety critical events, crash propensity, and other event specific explanatory variables. Owing to the presence of unobserved heterogeneity and omitted variable bias, fixed- and random-parameter discrete choice models are developed that relate crash propensity to unintentional driving volatility and other factors. Statistically significant evidence is found that driver volatilities in near-crash and crash events are significantly greater than volatility in normal driving events. After controlling for traffic, roadway, and unobserved factors, the results suggest that greater intentional volatility increases the likelihood of both crash and near-crash events. A one-unit increase in intentional volatility is associated with positive vehicular jerk in longitudinal direction increases the chance of crash and near-crash outcome by 15.79 and 12.52 percentage points, respectively. Importantly, intentional volatility in positive vehicular jerk in lateral direction has more negative consequences than intentional volatility in positive vehicular jerk in longitudinal direction. Compared to acceleration/deceleration, vehicular jerk can better characterize the volatility in microscopic instantaneous driving decisions prior to involvement in safety critical events. Finally, the magnitudes of correlations exhibit significant heterogeneity, and that accounting for the heterogeneous effects in the modeling framework can provide more reliable and accurate results. The study demonstrates the value of quasi-experimental study design and big data analytics for understanding extreme driving behaviors in safe vs. unsafe driving outcomes.

Longitudinal safety impacts of cooperative adaptive cruise control vehicle's degradation

INTRODUCTION

The adaptive cruise control (ACC) and cooperative ACC (CACC) systems are critical parts of self-driving vehicles. The ACC vehicles detect front vehicle' information via vehicle-mounted sensors and make longitudinal reactions automatically, while CACC vehicles enhance the performance by vehicle-to-vehicle (V2V) wireless communication. However, CACC vehicles may abruptly degrade to ACC mode in reality due to various reasons, including communication failures, driver manipulations, and cyber-attacks. The sudden degradation will definitely bring negative influences on safety.

METHOD

This study quantitatively evaluated the longitudinal safety impacts of vehicles' degradation in a CACC fleet based on microscopic simulations. The realistic CACC and ACC models proposed by the California Partners for Advanced Transit and Highways (PATH) were used for simulation experiments. The time integrated time-to-collision (TIT) was measured to quantify the collision risks. Extensive simulations were conducted via a fleet of 10 CACC vehicles and speed profiles of vehicles in different scenarios were compared. Key factors, including the leading vehicle's deceleration rate, the number of vehicles between degraded vehicles (NVDVs), threshold of TTC, and visibility were also examined via sensitivity analyses.

RESULTS AND CONCLUSIONS

Simulation results indicate that degradation has significant negative influences on longitudinal safety of degraded vehicles under the driving state of deceleration. Degradation at middle positions in a CACC fleet, such as fourth and fifth positions, is much safer than that at others. Moreover, nonadjacent degradation is much riskier than adjacent degradation at the front positions of a fleet. NVDVs can bring inverse impacts on safety with different degradation positions. Speed profiles imply that the hysteresis of degraded vehicles' speed control is the major reason for high collision risks. Practical applications: Appropriately, hierarchical countermeasures have the potential to reduce the longitudinal safety impacts of degradation. Findings of this study can contribute to determining the applicable length of CACC fleets.

The effect of gender, occupation and experience on behavior while driving on a freeway deceleration lane based on field operational test data

Deceleration lanes improve traffic flow by reducing interference, increasing capacity and enhancing safety. However, accident rates are higher on these interchange segments than on other freeway segments. It is important to attempt to reduce traffic accidents on these interchange segments by further exploring the behavior of different types of drivers on a highway deceleration lane. In this study, with field operational test (FOT) data from 89 driving instances (derived from 46 participants driving the test road twice) on a typical freeway deceleration lane, section speed profiles, vehicle trajectories, lane position and other key parameters were obtained. The lane-change characteristics and speed profiles of drivers with different genders, occupations and experiences were analyzed. The significant disparities between them reflects the risk associated with different groups of drivers. The study shows that male drivers changed to the outside lane earlier; professional drivers and experienced drivers made the last lane change as early as possible to enter the deceleration lane; and the speed of the vehicles entering the exit ramp was significantly higher than the speed limit. This research work provides ground truth data for deceleration lane design, driver ability training and off-ramp traffic safety management.

[Traumatic dissection of the left renal pedicle in a young adult]

Blunt trauma rarely causes renal pedicle dissection. Clinical signs are minimal and inconsistently reported. The diagnosis is based on computed tomographic angiography; arteriography is still useful when revascularization is considered. We report here a case of traumatic dissection with thrombosis of a juxta-aortic renal pedicle monitored in the intensive care unit. An endovascular procedure could not be proposed because of the juxta-aortic localization.

Evaluation of 6 and 10 Year-Old Child Human Body Models in Emergency Events

Emergency events can influence a child’s kinematics prior to a car-crash, and thus its interaction with the restraint system. Numerical Human Body Models (HBMs) can help understand the behaviour of children in emergency events. The kinematic responses of two child HBMs–MADYMO 6 and 10 year-old models–were evaluated and compared with child volunteers’ data during emergency events–braking and steering–with a focus on the forehead and sternum displacements. The response of the 6 year-old HBM was similar to the response of the 10 year-old HBM, however both models had a different response compared with the volunteers. The forward and lateral displacements were within the range of volunteer data up to approximately 0.3 s; but then, the HBMs head and sternum moved significantly downwards, while the volunteers experienced smaller displacement and tended to come back to their initial posture. Therefore, these HBMs, originally intended for crash simulations, are not too stiff and could be able to reproduce properly emergency events thanks, for instance, to postural control.

[Delayed liver hematoma development following deceleration injury]

Our report presents the case of a young woman who suffered liver trauma after electrical current injury and ensuing fall from an electricity pylon. The resulting intrahepatic hematoma manifested after a time interval of 48 hours following the injury, with initially negative CT scan.Key words: liver hematoma electrical current - polytrauma burns.

Pre-activation and muscle activity during frontal impact in relation to whiplash associated disorders

OBJECTIVE

For the evaluation of neck injury the relative distance was observed between a marker placed on the forehead and a marker placed on the shoulder and also by change of the angle. To compare the severity of head injury a value of maximum head acceleration was used, HIC and a 3 ms criterion. All criteria were related to the activity of musculus sternocleidomastoideus and musculus trapezius in a situation of expected or unexpected impact.

MATERIALS AND METHODS

The situation was recorded using a Qualisys system, head acceleration of probands in three axes was recorded using the accelerometer, activity of neck muscles was monitored by a mobile EMG.

RESULTS

Maximum head acceleration was 12.1 g for non-visual and 8.2 g for visual. HIC36 was 5.7 non visual and 4.0 for visual. 3-ms criterion was 11.5 g for non-visual and 7.8 g for visual. The average time of muscle activation of the observed group without visual perception is 0.027 s after hitting an obstacle, with visual perception 0.127 s before the crash.

CONCLUSIONS

Kinematic values indicate more favourable parameters for neck injuries for visual. Head injury criteria show an average decrease of about 30% for visual. We can conclude that the visual perception means a significant increase in pre-activation of the observed muscle group of almost 400% and lower activation in both following phases of approximately 40%.

Accuracy of a damage-based reconstruction method in NHTSA side crash tests

OBJECTIVE

Delta-V (ΔV), the magnitude of the velocity change experienced by a vehicle during a crash, is widely used as a predictor of injury risk. The National Automotive Sampling System/Crashworthiness Data System (NASS-CDS) uses the WinSMASH computer code to reconstruct ΔV based on postcrash vehicle deformation. WinSMASH, a direct descendant of CRASH3, first uses vehicle damage to estimate absorbed energy and then applies momentum conservation to estimate ΔV. This study aims to determine the accuracy of WinSMASH ΔV reconstructions for NHTSA side crash tests.

METHODS

This study is based upon 168 dynamic side impact tests conducted by the National Highway Traffic Safety Administration (NHTSA). For each crash test the actual ΔV for the struck vehicle was first determined from test instrumentation. WinSMASH was then used to reconstruct the struck vehicle ΔV for each test. WinSMASH-reconstructed ΔVs were compared to measured ΔVs for each test to assess reconstruction accuracy.

RESULTS

WinSMASH predicts ΔV at maximum crush, before restitution occurs. WinSMASH predictions of struck vehicle ΔV at maximum crush were 20 percent high on average when using vehicle specific stiffnesses, with a great deal of inter-case variability in the error. When compared to the total struck vehicle ΔV at separation (including restitution), WinSMASH overpredicted ΔV by 11 percent. WinSMASH overpredicted the amount of energy absorbed in collisions by 40 percent, which is consistent with overprediction of ΔV. When forced to reconstruct tests using the amount of absorbed energy calculated from the test data, error in WinSMASH ΔV effectively disappeared.

DISCUSSION

When reconstructing NHTSA side crash tests, WinSMASH overpredicts maximum crush ΔV by about 20 percent on average. The primary factors determining the amount of ΔV overprediction appear to be overprediction of absorbed energy and the assumption of zero restitution. WinSMASH vehicle side stiffness parameters are calculated based on artificially high energies; this may explain the overprediction of absorbed energy. WinSMASH's assumption of zero restitution partially masks the effect of energy overprediction. When given accurate reconstruction inputs and energy estimates, WinSMASH is capable of accurately reconstructing maximum crush ΔV in NHTSA side crash tests but cannot compensate for restitution.

Minimization of analytical injury metrics for head impact injuries

OBJECTIVE

To compare the predictions of the head injury criterion (HIC), currently used to predict the risk of traumatic brain injury in frontal vehicle impact and pedestrian impact tests, with the predictions of other empirical and analytical injury metrics.

METHODS

The appropriateness of different criteria relative to injury metrics derived from a head finite element (FE) model is investigated for different deceleration pulses in this research. Empirical injury metrics are computed by direct calculation for different analyzed pulses. In addition, for each pulse full FE model simulations of a complete human head were performed by means of the SIMon model. The computations are used to calculate the analytical injury metrics.

RESULTS

This article shows that an optimal head deceleration curve based on HIC does not minimize other analytical injury metrics. The results obtained in this study suggest that the HIC criterion does not necessarily provide the same severity ranking for different external loadings to the head as the injury metrics derived from the FE models.

CONCLUSION

Countermeasures designed based only on HIC could differ significantly from those based on analytical injury measures computed by FE models. The use of multiple injury metrics is recommended given that no scalar measure seems to be positively and strongly correlated with relevant injury metrics.

Sensitivity of THOR and Hybrid III dummy lower neck loads to belt systems in frontal impact

OBJECTIVES

To determine head-neck biomechanics with a focus on lower neck injury metrics in frontal impact. The mid- and large-size Hybrid III dummies and the mid-size Test device for Human Occupant Restraint (THOR) were positioned on a buck. Tests were conducted at low, medium, and high (3.3, 6.7, and 15.7 m/s) change in velocities using 3 restraint types: normal 3-point belt with no pretension (type A), 10-cm pretension (type B), and 200 N pretension (type C). Repeat tests were conducted. Measured vertical and shear forces and sagittal bending moments were evaluated at the upper and lower regions of the neck to different types of belt systems and at different change in velocities. Peak values normalized with respect to the belt type A were used in the comparative analysis. Metrics transformed to the occipital condyles and T1 were also evaluated.

RESULTS

All dummies showed good repeatability. Peak measured and transformed upper and lower neck moments were greatest in the large-size dummy. The mid-size Hybrid III dummy responded with greater forces and moments than the THOR. Regardless of dummy type, anthropometry, and velocity, peak lower neck moments were more sensitive to belt types than peak lower neck forces. A similar pattern was apparent for upper neck data. Moments in the THOR were more sensitive than moments in the mid-size Hybrid III dummy.

CONCLUSIONS

This study offers quantitative generic restraint-based data and addresses response differences between dummies and dummies of the same family. Because of increased sensitivity to belt types at the upper and lower necks for both forces and moments, the THOR appears to be an improvement to better assess injury potential to rear seat occupants wherein frontal impact air bags do not exist.

Caring for patients with traumatic injuries of the thoracic aorta

Trauma is a major cause of mortality and morbidity in the United States, with blunt traumatic injuries of the thoracic aorta continuing to occur despite the increased use of seatbelts and airbags. Emerging from crash analysis are effective interventions and provides increased awareness of the occult nature of these types of injuries. This article describes those interventions that healthcare providers must embed throughout the continuum of care for patients experiencing thoracic aortic injuries. Outcomes will be dependent upon the healthcare provider's knowledge of the physics of the event and the urgency of the diagnosis, as well as the ability to assess and manage all the variables involved. Current procedural issues are delineated and case studies are used to illustrate the processes of care needed by these patients.

Traumatic Innominate Artery Disruption and Aortic Valve Rupture

Rapid deceleration injury causing blunt thoracic trauma can result in injury to the thoracic aorta. Rupture of the aortic isthmus is the most common presentation; however, injury can occur more proximally in the arch vessels or the aortic root. We present an unusual case of simultaneous innominate artery disruption with aortic valve rupture after a motor vehicle accident, and we discuss issues surrounding the diagnosis and operative management of this rare, but life-threatening condition.

An Experimental Cadaveric Study for a Better Understanding of Blunt Traumatic Aortic Rupture

BACKGROUND

Blunt traumatic aortic rupture (BTAR) is a common catastrophic injury leading to death. Considerable uncertainty remains regarding the pathogenic cause. This study examines the comportment of the heart and the aorta during a frontal deceleration.

METHODS

Accelerometers were placed in the right ventricle of the heart, the aorta, the sternum, and the spine of six trunks removed from human cadavers. Different vertical decelerations were applied to cadavers and the relative motion of these organs was studied (19 tests).

RESULTS

The deceleration recorded in the isthmus of the aorta was always higher that the one recorded in the heart (p < 0.05). The difference of deceleration was 17% and increased with the speed's fall (extremes 5-25%). There was no significant difference of deceleration between the bony structures of the thorax. These results experimentally demonstrate for the first time that the fundamental mechanism of BTAR is sudden stretching of the isthmus of the aorta.

CONCLUSION

Four mechanisms are suspected to explain the location of the rupture: two hemodynamic mechanism (sudden increase of intravascular pressure and the water-hammer effect), and two physical mechanisms (sudden stretching of the isthmus and the osseous pinch). A greater understanding of the mechanism of this injury could improve vehicle safety leading to a reduction in its incidence and severity. Future work in this area should include the creation of an inclusive, dynamic model of computer-based modeling systems. This study provides for the first time physical demonstration and quantification of the stretching of the isthmus, leading to a computerized model of BTAR.

The contrecoup-coup phenomenon: a new understanding of the mechanism of closed head injury

A common observation in closed head injuries is the contrecoup brain injury. As the in vivo brain is less dense than the cerebrospinal fluid (CSF), one hypothesis explaining this observation is that upon skull impact, the denser CSF moves toward the site of skull impact displacing the brain in the opposite direction, such that the initial impact of the brain parenchyma is at the contrecoup location. A simple model was developed consisting of a balloon filled with water of density 1.00 g/mL enclosed in a clear plastic jar containing salt water of density 1.04 g/mL, simulating the same relative densities of the CSF and brain. The initial movement of the balloon, modeling the brain, was toward the contrecoup location with subsequent movement toward the coup location. The pattern of brain injury in which the contrecoup injury is greater than the coup injury is a result of initial movement of the brain in the contrecoup location. During the process of closed head injury, the brain parenchyma is initially displaced away from the site of skull impact and toward the contrecoup site resulting in the more severe brain contusion.

Post-traumatic descending aorta intramural haematoma fortuitously witnessed during a magnetic resonance examination of the spine

Most patients with traumatic aortic lesions of the thoracic aorta die at the accident site but 15% arrive at the hospital with vital signs. Digital subtraction angiography is considered the gold standard for the diagnosis of traumatic lesions of the thoracic aorta. Other non-invasive diagnostic techniques, such magnetic resonance and spiral computed tomography, proved to be reliable alternatives. Sometimes the diagnosis can be delayed by the relative lack of significant symptoms as well as the presence of unusual clinical findings. A case of post-traumatic intramural haematoma of the descending aorta revealed during a magnetic resonance of the spine is described. The final diagnosis was obtained with spiral computed tomography.

Understanding the mechanism of injury and kinetic forces involved in traumatic injuries

In this article, the author describes the kinetic forces patients can be subjected to during traumatic incidents or accidents and how these impact on injuries.

Early stabilization of traumatic aortic transection and mitral valve regurgitation with extracorporeal membrane oxygenation

We report a case of life-threatening aortic transection with concomitant mitral papillary muscle rupture and severe lung contusion caused by a failed parachute jump. This blunt thoracic injury was treated by early stabilization with extracorporeal membrane oxygenation followed by successful delayed graft repair of the descending aorta and mitral valve replacement with a mechanical prosthesis.

[Analysis of dynamic stress for human skull-brain under impact loading with acceleration and deceleration]

In this paper, we measure and analyze the changes of dynamic stress in human skull-brain under impact loading. By applying the frequency responding function and coherence function produced by the pressure of impact wave at each point on skull, and by use of the viewpoint of biomechanics, we further research into brain injuries and have got some data which cannot be obtained in clinical setting.

A retrospective review of air bag deaths

OBJECTIVE

To describe occupant and crash characteristics in the first 27 publicly released investigations of air-bag-related fatalities.

METHODS

A retrospective review of the first 27 released crash investigations of air-bag-induced fatalities was conducted. Data were obtained by the National Highway Traffic Safety Administration.

RESULTS

Three separate groups of occupants are described: adult drivers, school-aged children riding in the right front passenger seat, and infants installed into rear-facing infant car seats placed into the right front passenger seat. Female drivers were significantly likely to be short-statured. Male drivers tended to be slumped over the wheel. Eleven children (100%) were improperly restrained and thrown forward by preimpact braking. Adults tended to have serious chest injuries, while children tended to have CNS or neck injuries. All three infants had fatal CNS injuries. The average deltaV (change in the vehicle's velocity at the moment of impact) was 12 mph and the average bumper crash was 8.8 inches.

CONCLUSIONS

Air bags can cause fatal injury to car occupants in low- or moderate-speed crashes. Data suggest that proximity to the air bag at the time of deployment is the critical risk factor for fatal injury.

Aneurysm of the posterior inferior cerebellar artery caused by a traumatic perforating artery tear-out mechanism in a child

Traumatic posterior circulation aneurysms in the absence of fractures and penetrating wounds are extremely uncommon, especially in children. To our knowledge this is the first traumatic posterior inferior cerebellar artery(PICA) aneurysm reported that cannot be related to a skull fracture or a trauma caused by the edge of a rigid meningeal structure. In the present case, the initial subarachnoid hemorrhage (SAH) was caused by a perforating artery, originating from the PICA, which was torn out as the result of a deceleration trauma. Such a mechanism explains both the initial SAH and the development of the false aneurysm responsible for the second SAH.

Acceleration-deceleration injuries to the brain in blunt force trauma

Blunt force trauma to the stationary head is generally associated with cortical-subcortical injuries located at the site of impact (i.e., coup contusions). We present 2 cases of cerebral contusion injury secondary to falling tree limbs hitting the head, illustrating an exception to this observation. In each case, the most prominent lesions were white matter hemorrhagic contusions similar to those associated with acceleration-deceleration types of injuries characterizing falls or motor vehicle accidents (i.e., contrecoup contusions). The proposed pathogenesis for these observed lesions is a forceful impact resulting in the acceleration of the head and brain of a magnitude comparable with that in a motor vehicle accident or a fall.

Vertical deceleration injuries: a comparative study of the injury patterns of 101 patients after accidental and intentional high falls

We analysed the pattern of injury of 101 adult patients who were treated in our Trauma Center after a fall from an average height of 7.2 m between 1987 and 1990. In 62 patients the fall was accidental, and 39 jumped with suicidal intent. The most common injuries were fractures of the thoracic and lumbar spine (83.0 per cent) especially of the thoracolumbar junction. The pattern of limb injuries is towards a significant preference of the metaphyseal and epiphyseal parts of the bones of the distal joints (wrist, elbow, ankle, subtalar). Fractures of the diaphyseal areas and the proximal joints (shoulder, humerus, hip, femur) were rare. The incidence of thoracic (20.8 per cent) and pelvic injuries (30.0 per cent) was relatively lower. Blunt abdominal injury (5.9 per cent) was rare after a fall from a great height. Head injuries occurred in only 27 per cent of our patients who all survived their transport to hospital. There is no significant difference in injury patterns between deliberate and accidental falls, but there is a higher number of isolated injuries in all patients after unsuccessful suicidal jumps.

Temporomandibular joint injury potential imposed by the low-velocity extension-flexion maneuver

PURPOSE

It has been proposed that significant temporomandibular joint injury can occur as a result of rapid extension-flexion motion of the neck (whip-lash). This motion, which is experienced by passengers in vehicles that undergo rear-end collisions, has been described as causing rapid protrusion and opening of the mandible. It has been speculated that this relative motion between the mandible and the cranium produces forces at the temporomandibular joint (TMJ) that injure the articular elements. The objective of this study was to measure these forces by an experimental method.

MATERIALS AND METHODS

Accelerometer sensor and high-speed cinematographic data were obtained from the kinematic responses of live human test subjects positioned as occupants in motor vehicles that underwent staged low-velocity rear-end collisions. Linear and moment forces generated at the TMJs were obtained from the resultant acceleration pulse at the craniomandibular complex, estimation of the mass properties of the mandible and its appended soft tissues, and the application of Newton's Second Law of motion.

RESULTS

The maximum linear forces generated at the TMJ in a rear-end collision resulting in a velocity change of the test subject of 8 km/h (5 mph) were in the 7 to 10 N (1.6 to 2.2 lb) range. Moment forces at the joint peaked briefly at 0.55 N.m (4.81 lb-in).

CONCLUSIONS

These force magnitudes generated at the TMJ constitute a minor fraction of the forces experienced at the joint during normal physiologic function. It is a conclusion of this study that injuries to the TMJ attributed to low-velocity "whiplash" cannot be accounted for by the joint forces produced by this maneuver.

Successful renal autotransplantation in a patient with bilateral renal artery thrombosis

Bilateral renal artery thrombosis is a rare but traumatic injury that is most commonly caused by sudden deceleration. Traditional methods of repair (e.g., in situ repair, bypass graft, and thrombectomy) have poor success rates. This report is the first successful use of autotransplantation in a patient with bilateral renal artery thrombosis.

Autokabalesis: a study of intentional vertical deceleration injuries

Suicidal jumping from a height appears to be a seasonal problem in Glasgow. A series of 58 individuals were studied, giving a total of 60 jumping incidents. Of these, 21 were killed outright, and of 31 reaching hospital a further 11 subsequently died. Many were young, single, unemployed, adult males, the majority of whom had a known psychiatric diagnosis. Jump heights ranged from 1 to 27 floors and jumps from more than 6 floors were almost always fatal. Below this height mortality was related to the attitude of fall. Overall, 50 per cent mortality occurred at the 3rd floor. A wide range of multiple injuries were sustained and the Injury Severity Score was used to grade these for quantitative comparison. This was found to be highly discriminating between survival and non-survival.

A proposed new mechanism of traumatic aortic rupture: the osseous pinch

The currently accepted mechanism to explain traumatic aortic rupture from rapid deceleration involves a combination of traction, torsion, and hydrostatic forces. The authors hypothesize that aortic isthmus lacerations result from a pinch of the aorta between the spine and the anterior bony thorax (manubrium, clavicle, and first ribs) during chest compression caused by abrupt deceleration. Compression of an articulated, normally moving thoracic skeleton containing a synthetic aorta consistently caused transection of the aorta at the isthmus between the spine and anterior bony structures. Analysis of rotation of the first rib in 10 consecutive patients undergoing computed tomography of the chest demonstrated interposition of the distal aortic arch and isthmus between the vertebrae and anterior bony thorax in each instance. Aortas excised from laboratory dogs were pinched between structures simulating bones to reproduce intimal and medial lesions indistinguishable from lesions associated with naturally occurring traumatic disruptions. Although further studies in cadaveric specimens are necessary to confirm this mechanism of injury, the authors believe that their results support the osseous-pinch mechanism of aortic rupture.

Rupture of the supradiaphragmatic inferior vena cava by blunt decelerating trauma: case report

Lacerations of the inferior vena cava resulting from blunt external trauma are relatively rare, but extremely serious. The high lethality is due to the difficulty in diagnosis and technical problems with repair, particularly if the injury is located above the renal veins. During a 12-month period seven patients with inferior vena cava laceration were seen, of whom two presented with laceration of the inferior vena cava above the diaphragm. Both had a deceleration injury while wearing seatbelts. The clinical presentation was similar. The etiology is discussed. Caval continuity should be repaired because acute sudden occlusion at the suprahepatic level is incompatible with survival. Median sternotomy is advised, moreover it provides good exposure for eventual cannulation.

[Injuries and seat belts]

The effectiveness of the seat belt in reduction of road fatalities and injuries is well known. Nevertheless, improper or incorrectly wearing of the seat belt can induce specific cervical, thoracic or abdominal lesions. With reference to the literature and clinical reports, the authors describe the specific lesions of the seat belt syndrome. Superficial lesions are frequently associated with underlying deep lesions.

Spinal injury in a U.S. Army light observation helicopter

All accident reports involving U.S. Army OH-58 series helicopters were analyzed to determine vertical and horizontal velocity change at impact and the relationship of this kinematic data to the production of spinal injury. This analysis determined that spinal injury is related primarily to vertical velocity change at impact and is relatively independent of horizontal velocity change. The dramatic increase in the rate of spinal injury occurring just above the design sink speed of the aircraft landing gear (3.7 m/s) suggests that the fuselage and seat provide little additional impact attenuation capability above that of the gear alone. It is concluded that if this aircraft were modified to provide protection to the occupants for impacts up to 9.1 m/s (30 ft/s), approximately 80% of all spinal injury incurred in survivable accidents could be substantially mitigated. The incorporation of energy absorbing seats is recommended.

Changing trends with abdominal injury in seatbelt wearers

Seatbelts were incorporated as standard equipment for automobiles constructed in North America in 1964. The first seatbelt law was made mandatory in Canada as of 1 January 1971. Between January 1976 and January 1980 38 patients involved in automobile accidents while wearing passive restraints were treated at l'Hôpital du Sacré-Coeur: 32 of these 38 patients had signs and symptoms of abdominal injury. These patients wearing passive restraints had an unusually high incidence of gastrointestinal injury in comparison to previously reported patients not wearing restraints. Twenty-seven of the 32 patients had injury to the bowel or the bowel mesentery. This different spectrum of injuries is most likely related to the altered physics of rapid deceleration caused by restraint with the lap belt and shoulder harness.

Etiological factors in space motion sickness

We compared susceptibility to motion sickness during exposure to sudden-stop stimulation as a function of gravitoinertial force level. Our findings show that susceptibility is greatly enhanced, both with eyes-closed and eyes-open, for zero-g and 2-g conditions in parabolic flight compared with 1-g test conditions. The change in susceptibility is likely related to three factors: alterations in vestibulo-ocular function which result from variations in gravitoinertial force level (28,29); the altered pattern of otolithic activity resulting during variations in gravitoinertial force level; and the altered canal-otolith response synergies that result during exposure to gravitoinertial force levels greater or less than terrestrial levels. These factors are shown to be related to the etiology of space motion sickness and to the alterations in performance and vestibular function that are experienced by astronauts during reentry. An explanation is also proposed for the decrease in susceptibility to motion sickness exhibited by the Skylab astronauts inflight and for some period postflight during exposure to cross-coupled angular accelerations.

Major mediastinal vascular injuries

Surgical repair was carried out in 37 patients who had rupture of the thoracic aorta or major branches. The survival rate was 90% (33 of 37). Three deaths occurred in the acute phase, giving a survival rate of 87% (19 of 22). Two patients had severe coexisting brain trauma and the other had profuse intrathoracic hemorrhage before thoracotomy could be carried out. One death occurred in a chronic case (an arch aneurysm) for a survival rate of 94% (14 of 15). A massive air embolism to the brain caused this fatal outcome. There were no instances of left heart failure or renal shutdown in our series. One case of paraplegia occurred because a shunt was inserted erroneously in the distended adventitia from an enormous surrounding hematoma. The distal end of the shunt was not in the aortic lumen so there was no distal perfusion during the period of aortic clamping.

[Safety criteria in the problem of protection for the pilot's head against impact]

In order to determine man's tolerance, clinical symptoms of craniocerebral injuries were compared with physical characteristics of impacts. A ranking scheme of clinical manifestations of craniocerebral injuries as applied to specific flight conditions was developed. With respect to the craniocerebral injury biomechanics, clinical data were taken under statistical study, which helped to evaluate impact critical parameters and to propose a graphic scheme that can be used to describe in detail the accident and to estimate the probability of injuries of various degree over the entire range encountered in aviation and clinical practice.

Vertical deceleration injuries

Six patients simultaneously sustained vertical deceleration injuries. Vertical deceleration injuries are serious and characteristically involve major weight bearing structures with forces transmitted through the foot, leg, pelvis and vertebral column. Injuries of the lower extremity are likely to be unilateral and comminuted because the force of deceleration is applied to a small area. The severity of the injury increases by increasing the rate of deceleration and decreasing the distance through which the body is decelerated. More severe injury occurs when deceleration forces are applied to the body in the vertical axis compared with the transverse, provided that mass, velocity and stopping distance remain the same.