ADSEAT – Adaptive seat to reduce neck injuries for female and male occupants
Introduction
Whiplash Associated Disorders (WADs), also referred to as whiplash injuries, sustained in vehicle crashes is a worldwide problem. Estimates for the European Union, based on (Kullgren et al., 2007), indicate that 800,000 European Union citizens suffer whiplash injuries annually, of which 40,000 result in long term suffering and an associated socio-economic impact of approximately Euro 10 billion per annum Euro NCAP (2013). In Sweden, such injuries account for ∼70% of all injuries leading to disability due to vehicle crashes (Kullgren et al., 2007). The majority of victims experiencing initial neck symptoms recover within a few weeks or months of the crash (The Whiplash Commission, 2005), however, 5–10% of individuals experience different levels of medically classified permanent disabilities (Nygren et al., 1985, Krafft, 1998, The Whiplash Commission, 2005). Whiplash injuries occur at relatively low velocity changes (typically <25 km/h) (Eichberger et al., 1996, Kullgren et al., 2003), and in impacts from all directions, although rear impacts are most frequently featured in accident statistics (Watanabe et al., 2000).
Injury statistics from the mid 1960s until today show that females have a higher risk of sustaining whiplash injuries than males, ranging from 1.5 to 3 times higher (Kihlberg, 1969, O’Neill et al., 1972, Thomas et al., 1982, Otremski et al., 1989, Maag et al., 1990, Morris and Thomas, 1996, Dolinis, 1997, Temming and Zobel, 1998, Richter et al., 2000, Chapline et al., 2000, Krafft et al., 2003, Jakobsson et al., 2004, Storvik et al., 2009).
In general, concepts for whiplash protection seats have proved to be more effective for males than females (Kullgren and Krafft, 2010). The risk reduction of permanent medical impairment was approximately 45% for females and 60% for males. These results suggest that the effectiveness of different seat concepts may vary when occupied by males and females. It is important to further evaluate and understand the reasons behind such differences, in order to provide better protection for females in particular, as well as for males.
Females and males have different anthropometry and mass distribution, which may influence the interaction of the upper body with the seatback and head restraint, and consequently the injury risk. For example, the deflection of the seat frame, back rest padding and springs may depend on the mass and/or the centre of mass of the upper body with respect to the lever about the seatback hinge. The deflection of the seatback structures affects the plastic deformation, energy absorption and the dynamic head-to-head restraint distance, as well as the rebound of the torso (Svensson et al., 1993, Croft et al., 2002, Viano, 2003). The motion of the head relative to the head restraint may be affected by seated height in relation to the head restraint geometry. It has been reported that females have a somewhat different dynamic response in rear impact volunteer crash tests, such as a greater head x-acceleration, a greater (or similar) T1 x-acceleration, a lower (or similar) Neck Injury Criterion (NIC) value and a more pronounced rebound than males (Szabo et al., 1994, Siegmund et al., 1997, Hell et al., 1999, Welcher and Szabo, 2001, Croft et al., 2002, Mordaka and Gentle, 2003, Viano, 2003, Ono et al., 2006, Linder et al., 2008, Schick et al., 2008, Carlsson et al., 2010, Carlsson et al., 2011). In addition, there are anthropometric difference between males and females, such as stature (Pheasant and Haslegrave, 2006), weight, body part dimensions and mass distribution.
Crash test dummies are used when developing and evaluating the occupant protection performance of a vehicle. Today, females are not well represented, as the 50th percentile male crash test dummies currently used in low velocity rear impacts, the Biofidelic Rear Impact Dummy (BioRID) and the Rear Impact Dummy 3 Dimensional (RID3D), correspond to a ∼90–95th percentile female with regards to stature and mass (Welsh and Lenard, 2001). Consequently, current seats and whiplash protection systems are primarily adapted to the 50th percentile male without consideration for female properties, despite a higher whiplash injury risk in females.
In view of the above, a European research effort was initiated under the Adaptive Seat to Reduce Neck Injuries for Female and Male Occupants (ADSEAT) project. The overall objective of ADSEAT was to provide guidance on how to evaluate the protective performance of vehicle seat designs aiming to reduce the incidence of whiplash injuries. The work concentrates on evaluating the protective performance of seats beneficial to male, as well as, female motor vehicle occupants. By focusing project resources on the latter group, the influence gender and additional factors have on whiplash injury risk was established. The project aimed at establishing the properties of an average female to be implemented into a finite element model in order to provide an improved tool for the development and evaluation of adaptive systems, with special focus on whiplash injuries protection.
This study consists of six different parts aimed at different issues with regards to whiplash injury risk.
Aimed at performing a literature review on injury criteria and on male and female WAD risk based on real-world data, and to carry out database analyses, examining the WAD risk and anthropometric characteristics in WAD cases.
Aimed at establishing geometry and mass distribution of an average female seated in a car seat, based on findings in the literature.
Aimed at quantifying the dynamic response of female and male vehicle occupants by carrying out low severity rear impact sled volunteer tests.
Aimed at developing a finite element model of a crash test dummy representing an average female.
Aimed at analysing the relevance of currently used NIC to predict the injury risk in females, and to propose how to account for female injury risk in seat testing. Exploring the applicability of such recommendations by performing sled tests and computer simulations was also included in this part of the project.
Aimed at highlighting the differences between male and female vehicle occupants during a rear-end impact by using finite element simulations on a generic seat. In addition, this part of the project investigated different setups with respect to backrest angle, headrest position or head-to-headrest distance.
Section snippets
Real world data
An extensive literature review, searching for risk factors and injury criteria for males and females in published literature was performed. Several databases, including two sources of insurance data, were used to establish the size of female model to develop. Analysis of 2146 data sets of females, held on the AGU database, which holds technical and medical records of WAD sufferers, was carried out. The database contained measurements of whole body height and weight. The insurance company
Real world data
In the published literature, 249 articles based on real life data addressing risk factors for the incidence of WAD, specifically following rear end impacts, were identified. Furthermore, conference proceedings were screened, and an additional PubMed (US National Library of Medicine National Institutes of Health) and Google search for WAD risk factors, was performed. Searches included free combinations of terms like “whiplash”, Cervical Spine Distortion, “CSD”, “neck injury”, “risk”,
Discussion
According to real-world car crash records it is apparent that females have a higher risk of sustaining whiplash injuries, than males. One study has also shown that anti-whiplash concepts are more effective for males than females (Kullgren and Krafft, 2010). Studies have already revealed many differences between males and females which may influence the difference in injury risk, for example, differences in seated posture (Jonsson et al., 2007), muscle activity (Foust et al., 1973), and head to
Conclusions
The ADSEAT project has reviewed the whiplash injury risk, established anthropometric data of an average female, performed dynamic volunteer tests comprising females and males, developed a finite element model of an average female, and performed car seat tests with a dummy representing the size and weight of an average female.
A computational dummy model, called (Eva-female/RID-Rear Impact Dummy), of a 50th percentile female for use in rear impact tests was developed based on anthropometric data
Acknowledgements
This study was funded by the European Commission within the 7th Framework Programme. Additional funding has been received from the Swedish Transport Agency.
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2021, SSM - Population HealthCitation Excerpt :Indeed, the predominance of the male body in design and testing of car safety systems, reflects the widely documented under-representation of women's bodies in transport, medical and health research (Badstuber, 2019; Criado-Perez, 2019; Heidari et al., 2016; Law, 1999). In recent years, new simulation and crash test dummies have been developed that aim to better reflect variations in body size and age of the general population (Carlsson et al., 2014; Linder et al., 2013, 2018); the impact of such changes on injury is an important focus for future research. Indeed, to what extent car safety, car design and severity of crash contribute to the observed differences in hospitalised crashes between men and women needs further exploration.
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2019, Accident Analysis and PreventionCitation Excerpt :In order to identify the best performing occupant safety systems, it would be advantageous to use dummy models representing both parts of the adult population. To introduce such testing methods, an average sized female prototype dummy, the BioRID 50F (Linder et al. 2013), and a scaled down version of the BioRID 50M, was developed. To illustrate some of the geometrical differences between males and females, both models can be seen seated in the same seat, Fig. 3.
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2018, Accident Analysis and PreventionCitation Excerpt :Among the reasons that may affect different response to impacts, neck musculature strength (Vasavada et al., 2008) and reaction times (Siegmund et al., 2003), cervical fiber and ligament composition (Stemper et al., 2008), cervical vertebrae anatomical differences (Stemper et al., 2008), spinal alignment in seated postures (Sato et al., 2016) and the effect of these differences in simulated crashes (Sato et al., 2017) have been addressed. These studies have motivated the development of biomechanics research tools that better represent female average populations such as anthropomorphic devices (Schick et al., 2010; Carlsson et al., 2012; Linder et al., 2013) and human body numerical models (Kitagawa et al., 2015; Östh et al., 2017). The increased risk for concussion in female occupants we found in the current study was statistically significant only in frontal impacts and hence cannot be generalized to other crash configurations.
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2018, Accident Analysis and PreventionCitation Excerpt :However, the results from the simulations with the EvaRID tell another story for which the MP and HP generates a higher NICmax (and thus risk of injury) than the LP and thus the Concept Seat is expected to provide better injury protection than the Lab Seat. In addition, it has been suggested that a lower NIC threshold value should be applied for the female model (Schmitt et al., 2012; Linder et al., 2013). These differences cannot be distinguished through simulations exclusively using the FE-BioRID nor in physical test with the BioRID.
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