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In rear end collisions, the movement of the occupant can be subdivided into three phases: first, a relative rearward movement (towards the seat) occurs. Second, due to seat elasticity and deceleration of the car after the collision, the occupant reverses the direction of movement. Third, the forward-moving occupant is caught by the seat belts. The...
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Citations
... In contrast to the serial seat, the concept seat showed a considerable rebound of the back rest which is due to elasticity in the webbing and the dummy fell in to the restraint system in rebound. Therefore, it is useful to divide the crash into three phases, similar as earlier done for the low speed rear impact [14]: ...
With the introduction of fully-automated vehicles, new seating configurations of the passenger compartment has been proposed. Rearward facing front seats are considered to provide so-called living room seating. At least as long as conventional and fully-automated vehicles share the same roads in mixed traffic, crashes may occur. Occupant protection on a rearward facing seat must therefore be on the same level as on a forward facing seat to comply with legal requirements. In order to assess dummy response on a rearward facing seat in a 56 km/h full frontal impact, sled tests were performed, analysed, and discussed. A total of 23 sled tests in three series with a Hybrid III 50 th percentile adult male dummy were performed to simulate a vehicle frontal impact against a rigid barrier at impact speeds up to 56 km/h. In the first test series, a serial vehicle seat was used, but it showed already considerable deformation at an impact speed of 40 km/h. Therefore, a generic concept seat was developed. In the second test series, the concept seat was tested and tuned to enable it to perform tests at the target impact speed of 56 km/h. In the third series, tests to investigate repeatability were performed. Dummy loadings at 56 km/h were compared with reference values from legislation and literature. Focus was set on thorax and lumbar spine loadings. For a qualified interpretation of dummy loadings and the performance of the restraint system, the crash was divided into three phases: (1) impact phase until the maximum dummy rearward displacement, (2) dummy rebound before interaction with the seat belt, and (3) dummy in rebound and interaction with the seat belt. The impact phase (1) is characterized by the highest 3 ms chest acceleration, close to 60 g in 56 km/h tests. Notably, this was the loading closest to the injury assessment reference value (IARV). The lumbar spine was mainly loaded in compression with forces rising up to 5.8 kN. Chest deflection of about 8 mm was caused by inertia of the dummy rib cage. The rebound phase before interaction (2) did not show any substantial dummy loading. The rebound interaction phase (3) was influenced by the seat belt system, chest deflection ranged from 5 mm in the test with lap belts to 19 mm in the test with two crossed shoulder belts (crisscross belt). The viscous criterion was below 0.1 m/s in all tests. Overall, the tests showed good repeatability and the ability of the generic concept seat to control dummy kinematics. A limitation of our study is, that only full frontal loading directions were studied, dummy kinematics of oblique impact direction, simulating e.g. +30° impacts to the barrier, were not included. The head rest was not in focus of our investigation and the head was fixed to the head rest without any gap in between.
... The head and neck kinematics and kinetics observed in target vehicle occupants in these tests clearly show the effect of modern head restraints on optimizing head and neck kinematics and cervical flexion/extension moments in rear impacts [21]. Nearly two decades ago, Muser, et al. described head and neck kinematics in rear impacts as consisting of three phases [22]. In the first phase, the head initially translated rearward without rotation, resulting in a so-called "S-shaped" cervical spine with the upper neck in flexion and lower neck in extension. ...
... As observed in this study with a modern vehicle seat and head restraint, head restraint contact in rear impacts occurred very early in the kinematic sequence, with minimal neck motion and small neck forces and flexion/extension moments throughout. At all delta-Vs, upper neck flexion began prior to head restraint contact, consistent with the S-shape described by Muser et al. [22]. However, the lower neck exhibited an initial phase of subtle flexion loading (less than 10 N-m in all target vehicle ATDs), rather than the extension moment predicted for an S-shape. ...
... These thresholds, shown in Table VII, correspond with a 22% probability of sustaining serious neck injury (AIS+3) [74], which are associated with a risk of rupture of small blood vessels of the occipital condylar joints. An increasing N ij and N km are associated with ligament rapture, damage to the spinal cord, brainstem and death [74], [79], [80]. ...
... Neck injury criterion (N ij and N km ), is applied using neck injury thresholds, which is N ij =1 and N km =1, reported in [74], [77]. This indicates a 22% risk of serious neck injury (AIS+3) [74], which is associated with the rupture of small blood vessels of the occipital condylar joints, alar ligament rupture, damage to spinal cord (disc rupture and nerve root damage) and brainstem, and even death [74], [79], [80], [94]. Pedestrian impacts at the centreline of the vehicle were assessed for frontal impacts by the Neck Injury Criterion, N ij ., as shown in Fig. 10, which illustrated the upper neck load cases of the pedestrian impacts, calculated based on the combination of axial force and moment using (2). ...
Motor vehicle related pedestrian road traffic collisions are a major road safety challenge, since they are a leading cause of death and serious injury worldwide, contributing to a third of the global disease burden. The auto rickshaw, which is a common form of urban transport in many developing countries, plays a major transport role, both as a vehicle for hire and private use. The most common auto rickshaws are quite unlike the typical four wheel motor vehicle, is typically characterised by 3-wheels, a non-tilting sheet-metal body or open frame construction, a canvas roof and side curtains, a small driver's cabin, handlebar controls and a passenger space at the rear. Given the propensity, in developing countries, for auto rickshaws to be used in mixed cityscapes, where pedestrians and vehicles share the roadway, the potential for auto rickshaw impacts with pedestrians are relatively high. Whilst auto rickshaws are used in some Western countries, their limited number and spatial separation from pedestrian walkways, as a result of city planning has not resulted in significant accident statistics. Thus, auto rickshaws have not been subject to the vehicle impact related pedestrian crash kinematic analyses and/or injury mechanics assessment, typically associated with motor vehicle development in Western Europe, North America, and Japan. This present study presents a parametric analysis of auto rickshaw related pedestrian impacts by computational simulation, using a Finite Element model of an auto rickshaw and an LS-DYNA 50th percentile male Hybrid III Anthropometric Test Device (dummy). Parametric variables include auto rickshaw impact velocity, auto rickshaw impact area (front centre or offset) and relative pedestrian impact position (front, side, and rear). The output data of each impact simulation was correlated against reported injury metrics, Head Injury Criterion (front, side, and rear), Neck Injury Criteria (front, side, and rear), Abbreviated Injury Scale and reported risk level and adds greater understanding to the issue of auto rickshaw related pedestrian injury risk. The parametric analyses suggest that pedestrians are subject to a relatively high risk of injury during impacts with an auto rickshaw at velocities of 20 km/h or greater, which during some of the impact simulations may even risk fatalities. The present study provides valuable evidence for informing a series of recommendations and guidelines for making the auto rickshaw safer during collisions with pedestrians. Whilst it is acknowledged that the present research findings are based in the field of safety engineering and may over represent injury risk, compared to 'real world' accidents, many of the simulated interactions produced injury response values significantly greater than current threshold curves and thus, justify their inclusion in the study. To reduce the injury risk level and increase the safety of the auto rickshaw, there should be a reduction in the velocity of the auto rickshaw and, or, consideration of engineering solutions, such as retro fitting injury mitigation technologies to those auto rickshaw contact areas which are the subject of the greatest risk of producing pedestrian injury.
... Therefore, when assessing neck injury by determination of neck loads and injury criteria, the influence of the dummy is always inherent [e.g. Muser et al. 2000, 2002, Bortenschlager et al. 2007. ...
... 13 Different phases of a rear-end collision [adapted fromMuser et al. 2000]. ...
The potential for long-term impairment, including para- and quadriplegia, is always inherent in injuries to the spine and particular to the spinal cord. Of all spinal segments, the cervical spine is most frequently injured. Considering that the head and the neck form one functional entity, head loading often also implies neck loading. With respect to traffic accidents, severe (head-contact) cervical injuries are recorded from unbelted car occupants and motorcyclists (with or without helmet). The vast majority of cervical spine injuries, however, are minor soft tissue neck injuries usually graded as AIS1 and often not exhibiting a morphological manifestation. These injuries are both common and potentially debilitating.
... One measure is the time t between the sign change of the velocity of the head and that of the first thoracic vertebrae. According to [25], the maximum allowable t is 10 ms. Another measure is the frontal neck injury criterion FNIC [26], defined by ...
Passive in-vehicle safety systems such as the air bag and the belt restrain the occupant during a crash. However, often their behavior is not optimal in terms of occupant injuries. This paper discusses an approach to design an ideal restraint system. The problem is formulated as a feedback tracking problem with the objective to force the controlled variables, i.e., the acceleration of the head and the chest of the occupant, to follow a priori defined reference signals by simultaneous manipulation of the belt and the air bag. The reference signals have to reflect minimal injuries to the head, the chest, and the neck. More or less realistic numerical models of a crash test are far too complex to be used in control design processes. Therefore, a strategy is presented to derive simple, linear MIMO models. These models approximate the local dynamic behavior of the complex model and are suitable for control design. Analysis of the interactions in these simple models makes it plausible that the control design problem can be split into two separate tracking problems. Next, stabilizing low order controllers are designed using these models, and implemented in the closed loop system with the realistic numerical model. Results are presented, suggesting that feedback control with low order controllers is extremely effective as a basis for ideal restraint systems. Reductions of the adopted injury measures of at least 40% in comparison with the uncontrolled restraint system are achieved.
... Studies have analysed approaches to change the basic properties of a seat, like for example the stiffness. A general consensus whether it is better to increase or to decrease the seat stiffness was not reached (Svensson et al. 1993, Song et al. 1996, Muser et al. 2000). The head restraint stiffness has also received a controversial discussion with some advocating a stiffer head restraint for whiplash protection (Dippel et al. 1997) and others recommending a decreased head restraint stiffness (Jakobsson et al. 1993). ...
... Sled tests were performed with a car seat of a recent model to investigate the influence of the head restraint padding material with respect to whiplash injury protection. All sled tests were performed in the same manner according to the test procedure for the evaluation of the injury risk to the cervical spine in a low speed rear-end impact proposed for the ISO/TC22 N 2071 and ISO/TC22/ SC10, respectively (Muser et al. 1999). A BioRID II dummy was used as an anthropomorphic test device (Figure 1). ...
To prevent whiplash injury by appropriate seat design is the goal of various approaches presented in recent publications. In this context, the head restraint plays an important role, because its geometry as well as its dynamic behaviour greatly influences the occupant kinematics. This study focuses on the effect of the head restraint padding material. It was investigated whether the head restraint foam can be tailored to reduce whiplash injury. A novel formulation of a visco-elastic (VE) foam was chosen as padding material and was compared to a polyurethane (PU) foam commonly used today. The newly developed visco-elastic foam is characterised by a broad temperature range over which it keeps its advantageous deformation properties and therefore allows advanced energy dissipation. As such the visco-elastic foam fulfils an important requirement for use in an automotive application concerned with the interior of a vehicle. Applying the new foam as a head restraint padding material, sled tests and numerical simulations were performed to determine its possible beneficial effects. Both the experiments and the computational analysis mimicked conditions of rear-end collisions with delta-v values ranging from 16 km/h to 40 km/h. A BioRID II dummy was used as a human surrogate. The results indicate that the change of the foam become particularly effective at higher delta-v values. The loading of the head and neck in terms of maximal head acceleration and NICmax values can be reduced effectively by using visco-elastic foam. Additional changes of the head restraint geometry were shown to have large beneficial influence on the occupant kinematics.
... A higher pulse was estimated to have occurred where stiff vehicle structures engage. It has been suggested that cars produced in the late 1990's have a stiffer structure than those produced before this time and that this stiffness trend will continue (Muser 2001. During low speed insurance crashes reported that the newer vehicles tested produced stiffer pulses with higher peak magnitudes and of a shorter duration at similar delta V's. ...
Several proposals for a test procedure for neck injury protection assessment have been published. A good deal of data are available to serve as a basis for the choice of; test set-up (e.g. full vehicle test, sled test), accident severity (delta-v, acceleration characteristic) and crash dummy type. There is however a lack of information regarding the choice of a neck injury criterion and a tolerance level. There are however promising activities under way, for instance in the ongoing EU-project 'Whiplash II'. The EEVC adhoc working group on whiplash injuries recommends that a new EEVC activity on rear impact is established. Although much research work has taken place there are still significant gaps in the knowledge base, before a full regulatory test procedures can be fully adopted. The ad-hoc group feels that a new EEVC activity would have an important role to play in initiating and evaluating new research to fill these gaps. Future tasks for any new EEVC activity would include: a) Test procedures, b) Test devices (crash dummies), c) Assessment criteria, d) Validation
... Rebound velocity / T1 acceleration Muser et al. (2000) highlighted the potential importance of the rebound phase, where the occupant, having made contact with the seat and head restraint in the fist phase of the rear impact, is propelled forward into the seat belt. A large neck flexion may result during this phase of the impact. ...
div class="section abstract"> Peak upper and lower neck load data from rear impact crash testing were reviewed, aggregated, and analyzed from over 1,800 tests of existing peer-reviewed literature and research as well as available testing conducted by the Insurance Institute for Highway Safety (IIHS) and the National Highway Traffic Safety Administration (NHTSA). Both human volunteers and anthropomorphic test devices (ATDs) were subjects of the reviewed studies and testing.
Peak upper and lower neck axial forces (compression and tension), sagittal shear forces, and sagittal moments (flexion and extension) from available crash testing were reported and analyzed as functions of measured change in velocity (delta-V) ranging from approximately 3 to 60 km/h (1.9 to 37 mph). This load data was then further analyzed for possible trends amongst various testing conditions, such as seat type, ATD used, and subject seating position within the vehicle chassis and seat to develop a simple linear model. The linear regressions developed from rear impact crash testing suggest that a relationship does exist between peak cervical spine loading and delta-V. For the upper neck, peak tension and compression showed the highest correlations with respect to delta-V, seen in their calculated R2 values of 0.37 and 0.29, respectively. For the lower neck, peak tension and extension moments showed the highest correlations with respect to delta-V (R2 of 0.48 and 0.45, respectively) while peak compression had the lowest correlation (R2 = 0.08).
The same cervical spine loads were also aggregated from studies that measured loading in various activities of daily living (ADLs), such as everyday tasks and activities typically undergone by amusement park patrons and athletes. The analyzed ADLs produced cervical spine loading that was generally greater than or comparable to the aggregated data from crash testing and sled tests that underwent delta-Vs of less than approximately 24 km/h (15 mph), except for peak tensile forces. The data suggests that participants of related everyday activities may undergo peak cervical spine loading similar to what is experienced by normally seated occupants in lower-speed (delta-V less than 24 km/h (15 mph)) rear impact motor vehicle collisions.
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Rear-end collisions account for a significant portion of crashes each year and result in many soft tissue injuries. Several active vehicle safety systems have been developed to prevent rear-end collisions from the perspective of the striking vehicle, but at this time, there are limited vehicle systems designed to improve the safety of occupants in the struck vehicle in the case of an imminent collision. To address this shortcoming, the Pre Rear-End Positioning and Risk Extenuation System (PREPARES) was conceptualized, prototyped, and evaluated. Similar to current in-vehicle warnings, PREPARES was designed to elicit a response from drivers using salient and unexpected auditory and/or visual cues. However, unlike most warnings that inform or direct drivers’ attention toward a potential threat exterior to the vehicle, PREPARES attempts to direct drivers’ attention to a specific location inside the vehicle that consequently causes the driver to adjust their seating posture. This reactionary motion aims to recover the normal seated position within the seconds prior to impact, thus improving pre-crash positioning and potentially reducing the risk and severity of injuries. During this focused research effort, a proof-of-concept was obtained through human subject testing, which indicated that PREPARES improves driver pre-crash position. These initial results suggest that PREPARES is a potential strategy for mitigating injuries that warrants additional research and development.
