The influence of seated postures and anthropometry on lap belt fit in vehicle occupants: A 3D computed tomography study.

OBJECTIVE: In vehicle frontal collisions, it is crucial that the lap belt is designed to engage with the anterior superior iliac spine (ASIS) of occupants for a reliable restraint. This study aims to understand the influence of different seated postures on the geometrical relationship of the seat belt and the pelvis for various occupants using 3D upright and supine computed tomography (CT) systems. METHODS: The 3D shapes of bones and soft tissues around the pelvis were acquired through a CT scan for 30 participants. They were seated in a rigid seat equipped with a lap belt simulating the front seat of a small car, and wore a lap belt in three seated postures: upright, slouched and reclined. Parameters related to the likelihood of submarining occurrences, such as belt-ASIS overlap (an index for assessing the potential engagement of the lap belt with the ASIS) and the belt-pelvis angle (the difference between the belt angle and the normal direction of the anterior edge of the ilium) were compared. RESULTS: It was observed that the pelvis angle tilted rearward as the hip point was positioned forward and seatback angle increased. This can be seen in the slouched and reclined posture. The belt-pelvis angle was comparable between the slouched and the reclined postures, and was closer to zero (indicating that the lap belt path is closer to perpendicular to the anterior edge of the ilium) compared to the upright posture. In contrast, the belt-ASIS overlap increased with an increasing flesh margin of the ASIS and shallower belt angle. This suggests that the belt-pelvis angle is influenced by the seated posture whereas the belt-ASIS overlap is dependent more on an individual's anthropometry. The plot of belt-pelvis angle and belt-ASIS overlap exhibited significant variability among participants. CONCLUSIONS: The belt-pelvis angle and the belt-ASIS overlap of individuals will provide valuable information for understanding the current belt-fit location and predicting submarining occurrences for individuals in various postures when designing restraint systems.

Predictive modeling of submarining risk in car occupants based on pelvis angle and lap belt positioning.

OBJECTIVE: The engagement of the lap belt with the pelvis is critical for occupant safety during vehicle frontal crashes to prevent occupant submarining. This study aims to develop a predictive model for submarining risk based on anthropometric parameters and lap belt positioning using finite element (FE) analyses. METHODS: FE analyses were conducted using human body models representing various body shapes (a 50th percentile male, low and high BMI males, and a 5th percentile female) in three seated postures (standard, reclined, and slouched). The lap belt-ASIS overlap and the belt-pelvis angle were used as key parameters for predicting submarining risk. A logistic regression analysis was utilized to correlate submarining occurrence with the initial values of these two parameters at the beginning of impact. Subsequently, this submarining prediction model was applied to computer tomography (CT) measurements of human subjects in different seated postures (upright, reclined, and slouched), and submarining risks were calculated based on the developed model. RESULTS: FE simulations indicated that submarining was more likely to occur as the initial belt-pelvis angle approached zero and there was a smaller initial belt-ASIS overlap. The logistic regression analysis demonstrated that the initial belt-pelvis angle and belt-ASIS overlap were statistically significant for predicting submarining risk. The derived model effectively distinguished submarining occurrence based on the initial values of these two parameters. The application of the submarining model to CT measurements of human subjects showed that submarining risk was lower in the order of upright, slouched, and reclined postures. In the reclined posture, the high submarining risk was attributed to a small belt-ASIS overlap and a rearward-tilted pelvis angle; whereas in the slouched posture, the risk was mostly associated with a rearward-tilted pelvis angle. CONCLUSIONS: The submarining prediction model was developed based on the belt-pelvis angle and the belt-ASIS overlap. This predictive model may help to design restraint systems for various body types and seated postures of occupants.

Analysis of loading to the hip joint in fall using whole-body FE model.

Hip fractures caused by falls are important health problems for the elderly. Many studies used finite element (FE) models of the femur and its surroundings to evaluate the hip fracture risk during the impact phase in a fall. In this study, the whole-body human FE model (THUMS) of a small female was applied from the descent to the impact phase in a fall to understand the effect of the whole body. Brosh's material model was used for the soft tissue of the hip. A low-BMI and high-BMI model were developed based on THUMS (middle-BMI). For the middle-BMI model, the torso angle and the pelvis impact velocity were 45.2° and 2.62 m/s at the time of pelvis impact. The effective mass changed with time, and was 18.3 kg when the femoral neck force was maximum. The femoral neck force was 2.11 kN for the low-BMI model. The femoral neck forces when wearing a soft and a hard hip protector, and when falling on an energy-absorbing floor were compared for the FE models of human and a hip protector testing system. Though the force attenuation of the protective devices was 32.0-44.3 % in the testing system, the force attenuation in the middle-BMI was 0.1-22.2 %. In the low-BMI model, the attenuation of the soft protector was limited (4.2 %) because the hip protector protruded from the outer surface, so the contact force was concentrated at the hip region. This research suggests the importance of including the whole body to evaluate the hip fracture risk.

Analysis of fall kinematics and injury risks in ground impact in car-pedestrian collisions using impulse.

In vehicle-to-pedestrian collisions, pedestrian injuries occur due to contact with the car and the ground. Previous studies investigated pedestrian kinematic behavior using a parameter study or through statistical analysis although the force interaction between the pedestrian and the vehicle has not been considered. In this study, multibody analyses were conducted for vehicle-pedestrian collisions for adult and child pedestrian with various vehicle shapes. The impulse and impulse moment acting on the pedestrian from the vehicle were introduced, and the kinematic behavior, rotation and ground impact of the pedestrian model were examined. It was found that if an impulse moment acts on the pedestrian when the pedestrian re-contacts with the hood of the car, the angular velocity of the pedestrian's torso changes in the opposite direction (away from the car), and the torso angle prior to the ground contact decreases to less than 90°. This re-contact between the pedestrian and the vehicle was more likely to occur for cases where the collision involves an adult pedestrian, lower hood leading edge (HLE), longer hood length, and lower collision velocity. When the pedestrian torso angle in contact with the ground was less than 90°, the head vertical impact velocity with respect to the ground became less than 2.9 m/s which corresponds to the injury threshold of the head. This study demonstrated that pedestrian-vehicle re-contact is crucial for reducing ground injury. The vehicle shape, pedestrian size, and collision velocity can determine whether re-contact of the pedestrian with the vehicle occurs. This can then explain the factors affecting pedestrian ground impact injury (e.g., higher HLE, higher risk of ground head injury for children) that were shown in previous studies. A strategy to mitigate ground injury is to apply enough impulse moment onto the pedestrian's upper body from the hood in order to change the torso angular velocity during re-contact, thus making the torso angle less than 90°prior to the ground contact.

Shock-absorbing effect of flooring-adopted mechanical metamaterial technology and its influence on the gait and balance of older adults.

OBJECTIVE: To elucidate the performance of a shock-absorbing floor material with a mechanical metamaterial (MM-flooring) structure and its effect on the gait and balance of older adults. METHODS: The drop-weight impact was applied to evaluate the shock-absorbing performance. The falling weight was adjusted equivalent to the energy exerted on the femur of an older woman when she falls, which was evaluated on the MM-flooring and six other flooring materials.Nineteen healthy people over the age of 65 years participated in the gait and balance evaluations. The timed up and go and two-step tests were adopted as gait performance tests, and the sway-during-quiet-balance test with force plates and the functional reach test (FRT) were adopted as balance tests. All the participants underwent these tests on the MM-flooring, shock-absorbing mat and rigid flooring. RESULTS: The shock-absorbing performance test revealed that MM-flooring has sufficient shock-absorbing performance, and suggesting that it may reduce the probability of fractures in the older people when they fall. The results of the gait performance test showed that the participants demonstrated the same gait performance on the MM-flooring and the rigid floor. In the quiet standing test, MM-flooring did not affect the balance function of the participants to the same extent as the rigid floor, compared with the shock-absorbing mat. In the FRT, no significant differences were found for any of the flooring conditions. CONCLUSIONS: MM-flooring has the potential to prevent fractures attributed to falls and does not affect the gait or balance of older adults.

Experimental study on car collisions with bicycles equipped with child seats.

In Japan, traffic accidents involving bicycles have become a serious problem as a result of the increase in the use of bicycles due to the rising concerns of environmental and health problems. In recent years, bicycles equipped with child seats have become a popular means of transportation for preschool children in urban areas in Japan. Under such adverse circumstances, it is necessary to conduct more studies and evaluations to prevent traffic accidents and the resulting injuries involving bicycles with children. For accident prevention and damage mitigation, this study mainly aims to understand the kinematic behavior and injury risk of children in collisions involving bicycles equipped with child seats through experiments. First, fall tests were conducted to evaluate the effect of the integrated head restraints (also commonly known as headrests) of child seats. It was confirmed that head restraints can reduce the impact of head collisions with the road surface. Second, side collision tests were conducted between a car and a bicycle equipped with a child seat, and the effects of the seat belt and head restraint of the child seat were investigated. It was shown that the kinematic behavior of the child dummy significantly was changed depending on wearing the seat belt. In the condition that the seat belt was not fastened, the child dummy was ejected out of the child seat while rotating toward the hood after the impact with the front of the car. In contrast, when the seat belt was fastened, the child dummy was restrained in the child seat and moved together with the bicycle from the start of the collision until the complete stop. Thus, it was found that using child seats with head restraints and using seat belts can reduce the risk of injury to children during an impact with the road surface, because the child dummy in the tests impacted the road surface only after the bicycle already had contact with the road surface.

Molecular mechanisms of cyclic phosphatidic acid-induced lymphangiogenic actions in vitro.

The lymphatic system plays important roles in various physiological and pathological phenomena. As a bioactive phospholipid, lysophosphatidic acid (LPA) has been reported to function as a lymphangiogenic factor as well as some growth factors, yet the involvement of phospholipids including LPA and its derivatives in lymphangiogenesis is not fully understood. In the present study, we have developed an in-vitro lymphangiogenesis model (termed a collagen sandwich model) by utilizing type-I collagen, which exists around the lymphatic endothelial cells of lymphatic capillaries in vivo. The collagen sandwich model has revealed that cyclic phosphatidic acid (cPA), and not LPA, augmented the tube formation of human dermal lymphatic endothelial cells (HDLECs). Both cPA and LPA increased the migration of HDLECs cultured on the collagen. As the gene expression of LPA receptor 6 (LPA6) was predominantly expressed in HDLECs, a siRNA experiment against LPA6 attenuated the cPA-mediated tube formation. A synthetic LPA1/3 inhibitor, Ki16425, suppressed the cPA-augmented tube formation and migration of the HDLECs, and the LPA-induced migration. The activity of Rho-associated protein kinase (ROCK) located at the downstream of the LPA receptors was augmented in both the cPA- and LPA-treated cells. A potent ROCK inhibitor, Y-27632, suppressed the cPA-dependent tube formation but not the migration of the HDLECs. Furthermore, cPA, but not LPA, augmented the gene expression of VE-cadherin and ß-catenin in the HDLECs. These results provide novel evidence that cPA facilitates the capillary-like morphogenesis and the migration of HDLECs through LPA6/ROCK and LPA1/3 signaling pathways in concomitance with the augmentation of VE-cadherin and ß-catenin expression. Thus, cPA is likely to be a potent lymphangiogenic factor for the initial lymphatics adjacent to type I collagen under physiological conditions.

The Head AIS 4+ Injury Thresholds for the Elderly Vulnerable Road User Based on Detailed Accident Reconstructions.

Compared with the young, the elderly (age greater than or equal to 60 years old) vulnerable road users (VRUs) face a greater risk of injury or death in a traffic accident. A contributing vulnerability is the aging processes that affect their brain structure. The purpose of this study was to investigate the injury mechanisms and establish head AIS 4+ injury tolerances for the elderly VRUs based on various head injury criteria. A total of 30 elderly VRUs accidents with detailed injury records and video information were selected and the VRUs' kinematics and head injuries were reconstructed by combining a multi-body system model (PC-Crash and MADYMO) and the THUMS (Ver. 4.0.2) FE models. Four head kinematic-based injury predictors (linear acceleration, angular velocity, angular acceleration, and head injury criteria) and three brain tissue injury criteria (coup pressure, maximum principal strain, and cumulative strain damage measure) were studied. The correlation between injury predictors and injury risk was developed using logistical regression models for each criterion. The results show that the calculated thresholds for head injury for the kinematic criteria were lower than those reported in previous literature studies. For the brain tissue level criteria, the thresholds calculated in this study were generally similar to those of previous studies except for the coup pressure. The models had higher (>0.8) area under curve values for receiver operator characteristics, indicating good predictive power. This study could provide additional support for understanding brain injury thresholds in elderly people.

An increase in normetanephrine in hair follicles of acne lesions through the sympatho-adrenal medullary system in acne patients with anxiety.

Acne vulgaris, a chronic inflammatory skin disease, has been associated with not only sebaceous gland dysfunction but also various endogenous and exogenous stresses. Since sebaceous glands are under neuroendocrine control, including the hypothalamic-pituitary-adrenal axis and neuro-autocrine mechanisms, it remains unclear how psychological stress relates to the pathogenesis of acne. In this study, we investigated the relationship between psychological stress and catecholamine in acne lesions from 18 patients with mild or moderate acne. The State-Trait Anxiety Inventory (STAI) revealed that all patients were anxious, with six having low anxiety and 12 high anxiety. Salivary α-amylase activity (sAA), which is regulated by the sympatho-adrenal medullary (SAM) system, positively correlated with the STAI State Anxiety scores (STAI-S) and was significantly detectable in acne patients with high rather than low anxiety. In addition, the level of normetanephrine, but not metanephrine, both of which are catecholamine metabolites, in hair follicles of acne lesions also positively correlated with the STAI-S. Furthermore, the normetanephrine level was higher in patients with high rather than low anxiety, whereas there was no change in metanephrine in the hair follicles of the acne lesions. Moreover, neither the sAA nor metanephrine and normetanephrine in the acne lesions was related to acne severity in the patients. Thus, these results provide novel evidence that a SAM system-associated increase of normetanephrine level in hair follicles is involved in the acne pathology of patients with anxiety.

Lysophosphatidic Acid Augments the Gene Expression and Production of Matrix Metalloproteinases-1 and -3 in Human Synovial Fibroblasts in Vitro.

Rheumatoid arthritis (RA) is an inflammatory disease with joint dysfunction following cartilage degradation. The level of lysophosphatidic acid (LPA) has been reported to be augmented in human synovial fluid from patients with RA. However, it remains to be elucidated whether LPA participates in cartilage destruction. In the present study, we have demonstrated that the production of promatrix metalloproteinases (proMMPs)-1 and -3 was augmented along with an increase of extracellular signal-regulated kinase (ERK)1/2 phosphorylation through LPA receptor 1 (LPAR1) in human synovial fibroblasts. These results suggest that LPA transcriptionally increases MMP production by the activation of an LPAR1/ERK1/2 signal pathway in human synovial fibroblasts. Thus, LPA is likely to be a pathological candidate for cartilage degradation in RA.

Analysis of Lap Belt Fit to Human Subjects using CT Images.

In vehicle collisions, the lap belt should engage the anterior superior iliac spine (ASIS). In this study, threedimensional (3D) shapes of bones and soft tissues around the pelvis were acquired using a computed tomography (CT) scan of 10 male and 10 female participants wearing a lap belt. Standing, upright sitting, and reclined postures were scanned using an upright CT and a supine CT scan system. In the upright sitting posture, the thigh height was larger with a higher BMI while the ASIS height did not change significantly with BMI. As a result, the height of the ASIS relative to the thigh (ASIS-thigh height) became smaller as the BMI increased. Because the thigh height of females was smaller than that of males, the ASIS-thigh height was larger for females than for males. As the ASIS-thigh height was larger, the overlap of the lap belt with the ASIS increased. Thus, the lap belt overlapped more with the ASIS for the females than for the males. The abdomen outer shape is characterized by the trouser cord formed valley, the torso/thigh junction, and the anterior convexity formed between them depending on the adipose tissues. The abdomen outer shapes changed from the standing, the reclined posture to the upright sitting posture. In the reclined sitting posture, the lap belt is positioned upward and rearward relative to the ASIS, and the overlap of the lap belt with the ASIS was smaller compared to the upright posture.

Analysis of car driver responses to avoid car-to-cyclist perpendicular collisions based on drive recorder data and driving simulator experiments.

The reduction of cyclist injuries and fatalities is one of the important issues in traffic safety. To establish countermeasures to avoid collisions, it is necessary to understand driver's responses in such critical situations. From videos of drive recorders, the behavior of cyclists and drivers that led to car-to-cyclist collisions can be analyzed objectively. In this research, the drivers' responses to avoid car-to-cyclist perpendicular collisions were examined using videos of drive recorders, and through using a driving simulator. First, drivers' responses to avoid collisions were compared between near-miss incidents and actual collisions using videos from drive recorders. In a statistical analysis of selected parameters of the drivers' responses, the average values of different parameters such as the time-to-collision (TTC), the deceleration at the time the cyclist was first visible to the driver, and the braking reaction time (BRT) were significantly different between near-miss incidents and collisions. Applying logistic regression to the near-miss and collision data revealed that the BRT at the time the cyclist was first visible had the largest influence on collision occurrences. The velocity-TTC, and the velocity-distance graphs at the time of braking-onset was plotted; the car deceleration of 5.2 m/s2 was the threshold which discriminated near-miss and collisions. Second, the responses of people to avoid collisions against cyclists were investigated in a driving simulator. Based on real-world collision videos from the drive recorders, two scenarios were reconstructed where the crossing cyclist appeared suddenly from behind view-blocking obstructions at an intersection. Scenario A has a relatively large TTC of 1.9 s, and scenario B had a small TTC of 0.5 s. The BRT was significantly smaller in the group that avoided collisions than in the group that collisions occurred in scenario A, whereas all parameters (TTC, BRT, and car deceleration) were all significantly smaller in the group that avoided collision in scenario B. The driver response parameters (TTC, BRT and car deceleration) were comparable between the drive recorder data and the driving simulator experiments. It was demonstrated that the BRT is the most important parameter toward avoiding collisions. Some drivers who accelerated the cars at the intersections had large BRT, and this led to collisions. Additionally, it was observed that swerving of cars without braking was not effective for collision avoidance.

Analysis of kinematic behavior of pedestrians/cyclists in vehicle collisions using impulse.

Objective: In order to further reduce the injury risks to pedestrians/cyclists in vehicle collisions, it is necessary to control pedestrian/cyclist kinematics. To investigate pedestrian/cyclist kinematic behavior from initial contact with the vehicle to the ground contact, it is necessary to evaluate the force interactions between the pedestrian/cyclist body region and the car body during the crash event.Method: Finite element analysis was conducted for models of pedestrians and cyclists being struck by a car around the center, left, and right sides of the front of the vehicle at 40 km/h. The impulse that was applied to each body region of the pedestrian/cyclist by the vehicle body during the impact was employed to analyze the kinematic behavior of the pedestrian/cyclist.Results: An impulse-time history can be separated into three stages. In the first stage, the pedestrian/cyclist was accelerated by the vehicle's forward impulse imparted to the subject due to the lower extremities contacting the bumper and hood leading edge. In the second stage, the pedestrian/cyclist rotates around the hood leading edge. In the third stage, the pedestrian/cyclist was accelerated in the vehicle forward and upward directions by the impulse resulting from the contact of the head and upper extremities with the cowl and the windshield. As the impulse to the lower extremity increased, the wraparound distance (WAD) decreased; however, the pelvis velocity in the forward direction increased.Conclusion: This research employed a new approach using the impulse transmitted to each body region due to contact with the vehicle body and showed that impulse is a useful parameter to understand the process of pedestrian/cyclist kinematics. The impulse relates to the linear and angular velocities of the pedestrian/cyclist at the time of separation from the car, thereby providing useful information to control pedestrian/cyclist falling kinematics prior to the ground impact.

A new approach for uncertainty analysis of ETW Rider Head Injury Reconstruction via Coupling Response Surface and Monte Carlo methodologies.

Traditional vehicle accident reconstructions do not take into account all existing uncertainties and may over- or under-estimate the injury risk. The objective of this study was to introduce a new uncertainty analysis method by applying Response Surface-Monte Carlo Methods (RS-MCM) to predict head injury risk in real electric two wheelers (ETW) to vehicle accidents. Vehicle impact velocity ranges in three detailed ETWs accidents (including video records and injury reports) were estimated using direct linear transformation (DLT) or video frame (VF) methods. A response surface methodology (RSM) was used to obtain an approximate model of the each real ETW accident, and a vehicle impact velocity distribution was estimated by applying the Monte Carlo Method (MCM) to the resulting model. If the velocity distribution was in agreement with the initial estimated velocity, the reconstruction quality was deemed acceptable. The injury severity was then assessed using the initial conditions resulting from the range of potential head impact conditions identified in the reconstruction activities. The identified head linear and angular impact velocities were input to finite element analyses to the THUMS Ver4.02 pedestrian head model and resulting in head injury criteria (HIC). The HIC values were further explored using the same RSM method used earlier to establish impact conditions. The distribution of reconstructed AIS levels show good agreement with the injury results from forensic reports. The results illustrated that the RS-MCM enriches the information for head trauma injury mechanisms caused by the vehicle collisions or ground impact.

Antineuropathic pain actions of Wu-tou decoction resulted from the increase of neurotrophic factor and decrease of CCR5 expression in primary rat glial cells.

Wu-tou decoction (WTD), a classic Traditional Chinese medicine formula, has been extensively used in the treatment of neuropathic pain (NP) such as chronic inflammatory pain, trigeminal neuralgia, and cancer-induced pain. Our previous studies have shown that the severity of mechanical allodynia and thermo hypersensitivity in NP rats are reduced by WTD, of which analgesic candidates are paeoniflorin (Pae) and liquiritin (Liq). The aim of this study was to clarify the molecular mechanisms of WTD, Pae and Liq against NP based on the primary rat glial cells in vitro. The gene expression levels of neurotrophic factors such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), and Artemin and C-C chemokine receptor type 5 (CCR5) were augmented by inflammatory cytokines, while chemokines increased only CCR5 gene expression. The constitutive and cytokine-augmented neurotrophic factor gene expression was enhanced by WTD, Pae, and Liq through PI3K- and PKA-dependent pathways in rat glial cells, leading to the increase of NGF and BDNF production. Furthermore, the CCR5 gene expression under basal and chemokine-treated conditions was suppressed by these reagents, in which signal pathway(s) was independent on the activation of PI3K and PKA. Moreover, there was no cytotoxicity in the WTD, Pae, and Liq treatments in glial cells. Thus, these results provide a novel evidence that WTD may exert the anti-NP actions by predominantly increasing the production of neurotrophic factors through PI3K- and PKA-signaling pathways in rat glial cells. Furthermore, Pae and Liq may play as analgesic candidates in WTD-mediated NP management.

Chest compression of a pregnant woman by a seatbelt might affect fetal outcome, even in minor to moderate frontal vehicle collisions.

INTRODUCTION: Pregnant women often suffer from negative fetal outcomes, despite wearing a seatbelt correctly. When restrained vehicle passengers are involved in a frontal collision without suffering from any injuries, the forces they experience are particularly concentrated in the chest because of the seatbelt. We analyzed the biomechanics of chest injuries sustained by restrained pregnant drivers and possible effects of these injuries on the fetus. MATERIAL AND METHODS: The Maternal Anthropometric Measurement Apparatus dummy, version 2B, representing a pregnant woman at 30 weeks of gestation, was used. Sled tests were performed for recreating frontal impact situations with vector velocity changes at impact speeds of 13, 26, and 40km/h. Overall kinematics of the dummy were examined using high-speed video imaging. Quantitative dummy responses, such as time course of acceleration of the sled and chest, pressure of the belt, and deflection of the chest (right and left) during impact were also measured. RESULTS: Although collision velocities were different, the distances of forward movement of the dummy were similar (121-129mm) owing to the safety devices. However, maximum deflection of the chest (35.4mm to the left and 15.7mm to the right) was obtained at a 26-km/h collision. Additionally, maximum deflection of 28.7mm to the left and 10.9mm to the right of the chest were obtained at 40km/h. CONCLUSIONS: Because the uterus enlarges and the fundus reaches the lower part of the rib cage during late pregnancy, we consider that the reason for negative fetal outcomes is partly owing to chest compression and subsequent applied forces on the uterus, even in minor to moderate frontal collisions. This knowledge may be useful for forensic scientists who determine the causes and mechanisms of a fetal death or the offenders' responsibilities for both maternal and fetal outcomes when the mother is involved in a frontal vehicle collision.

AEB effectiveness evaluation based on car-to-cyclist accident reconstructions using video of drive recorder.

OBJECTIVE: Though autonomous emergency braking (AEB) systems for car-to-cyclist collisions have been under development, an estimate of the benefit of AEB systems based on an analysis of accident data is needed for further enhancing their development. Compared to the data available from in-depth accident data files, data provided by drive recorders can be used to reconstruct car-to-cyclist collisions with greater accuracy because the position of cyclists can be observed from the videos. In this study, using data from drive recorders, the performance and limitations of AEB systems were investigated. METHOD: Data of drive recorders involving taxi-to-cyclist collisions were collected. Using the images collected from the drive recorders of those taxis, 40 cases of 90° car-to-cyclist intersection collisions were reconstructed using PC-Crash. Then, the collisions were reconstructed again utilizing car models with AEB systems installed while changing the sensor's field of view (FOV) and the delay time of initiating vehicle deceleration. RESULTS: The angle of FOV has a significant influence on avoiding car-to-cyclist collisions. Using a 50° FOV with a braking delay time of 0.5 s resulted in avoiding 6 collisions, and using a 90° FOV resulted in avoiding an additional 14 collisions. Even when installing an ideal AEB system providing 360° FOV and no delay time for braking, 8 collisions were not avoided, though the impact velocities were reduced for all of these remaining collisions. These collisions were caused by the cyclists' sudden appearance in front of cars, and the time-to-collision (TTC) when the cyclists appeared was less than 0.9 s. CONCLUSION: The AEB systems were effective for mitigating collisions that occurred due to driver perception delay. Because cyclists have a traveling velocity, a wide-angle FOV is effective for reduction of car-to-cyclist intersection collisions. The reduction of delay time in braking can reduce the number of collisions that are close to the braking performance limit. The collisions that remained even with an ideal AEB system in the PC-Crash simulation indicate that such collisions could still occur for autonomous cars if the traffic environment does not change.

Difference between car-to-cyclist crash and near crash in a perpendicular crash configuration based on driving recorder analysis.

Analyzing a crash using driving recorder data makes it possible to objectively examine factors contributing to the occurrence of the crash. In this study, car-to-cyclist crashes and near crashes recorded on cars equipped with advanced driving recorders were compared with each other in order to examine the factors that differentiate near crashes from crashes, as well as identify the causes of the crashes. Focusing on cases where the car and cyclist approached each other perpendicularly, the differences in the car's and cyclist's parameters such as velocity, distance and avoidance behavior were analyzed. The results show that car-to-cyclist crashes would not be avoidable when the car approaching the cyclist enters an area where the average deceleration required to stop the car is more than 0.45 G (4.4 m/s2). In order for this situation to occur, there are two types of cyclist crash scenarios. In the first scenario, the delay in the drivers' reaction in activating the brakes is the main factor responsible for the crash. In this scenario, time-to-collision when the cyclist first appears in the video is more than 2.0 s. In the second scenario, the sudden appearance of a cyclist from behind an obstacle on the street is the factor responsible for the crash. In this case, the time-to-collision is less than 1.2 s, and the crash cannot be avoided even if the driver exhibited avoidance maneuvers.

Analysis of pedestrian-to-ground impact injury risk in vehicle-to-pedestrian collisions based on rotation angles.

INTRODUCTION: Due to the diversity of pedestrian-to-ground impact (secondary impact) mechanisms, secondary impacts always result in more unpredictable injuries as compared to the vehicle-to-pedestrian collisions (primary impact). The purpose of this study is to investigate the effects of vehicle frontal structure, vehicle impact velocity, and pedestrian size and gait on pedestrian-to-ground impact injury risk. METHOD: A total of 600 simulations were performed using the MADYMO multi-body system and four different sizes of pedestrians and six types initial gait were considered and impacted by five vehicle types at five impact velocities, respectively. The pedestrian rotation angle ranges (PRARs) (a, b, c, d) were defined to identify and classify the pedestrian rotation angles during the ground impact. RESULTS: The PRARs a, b, and c were the ranges primarily observed during the pedestrian landing. The PRAR has a significant influence on pedestrian-to-ground impact injuries. However, there was no correlation between the vehicle velocity and head injury criterion (HIC) caused by the secondary impact. In low velocity collisions (20, 30km/h), the severity of pedestrian head injury risk caused by the secondary impact was higher than that resulting from the primary impact. CONCLUSIONS: The PRARs defined in this study are highly correlated with the pedestrian-to-ground impact mechanism, and can be used to further analyze the pedestrian secondary impact and to predict the head injury risk. PRACTICAL APPLICATIONS: To reduce the pedestrian secondary impact injury risk, passive and active safety countermeasures should be considered together to prevent the pedestrian's head-to-ground impacts, particularly in the low-velocity collisions.

Application of energy derivative method to determine the structural components' contribution to deceleration in crashes.

OBJECTIVE: For occupant protection, it is important to understand how a car's deceleration time history in crashes can be designed using efficient of energy absorption by a car body's structure. In a previous paper, the authors proposed an energy derivative method to determine each structural component's contribution to the longitudinal deceleration of a car passenger compartment in crashes. In this study, this method was extended to 2 dimensions in order to analyze various crash test conditions. The contribution of each structure estimated from the energy derivative method was compared to that from a conventional finite element (FE) analysis method using cross-sectional forces. METHOD: A 2-dimensional energy derivative method was established. A simple FE model with a structural column connected to a rigid body was used to confirm the validity of this method and to compare with the result of cross-sectional forces determined using conventional analysis. Applying this method to a full-width frontal impact simulation of a car FE model, the contribution and the cross-sectional forces of the front rails were compared. In addition, this method was applied to a pedestrian headform FE simulation in order to determine the influence of the structural and inertia forces of the hood structures on the deceleration of the headform undergoing planar motion. RESULT: In an oblique impact of the simple column and rigid body model, the sum of the contributions of each part agrees with the rigid body deceleration, which indicates the validity of the 2-dimensional energy derivative method. Using the energy derivative method, it was observed that each part of the column contributes to the deceleration of the rigid body by collapsing in the sequence from front to rear, whereas the cross-sectional force at the rear of the column cannot detect the continuous collapse. In the full-width impact of a car, the contributions of the front rails estimated in the energy derivative method was smaller than that using the cross-sectional forces at the rear end of the front rails due to the deformation of the passenger compartment. For a pedestrian headform impact, the inertial and structural forces of the hood contributed to peaks of the headform deceleration in the initial and latter phases, respectively. CONCLUSIONS: Using the 2-dimensional energy derivative method, it is possible to analyze an oblique impact or a pedestrian headform impact with large rotations. This method has advantages compared to the conventional approach using cross-sectional forces because the contribution of each component to system deceleration can be determined.