Elsevier

Accident Analysis & Prevention

Volume 60, November 2013, Pages 334-343
Accident Analysis & Prevention

ADSEAT – Adaptive seat to reduce neck injuries for female and male occupants

https://doi.org/10.1016/j.aap.2013.02.043Get rights and content

Highlights

  • We developed EvaRID, the world's first virtual crash test dummy of an average female.

  • Specified anthropometric data of an average female crash test dummy model.

  • Performed dynamic volunteer sled tests comprising females and males.

  • Suggested new whiplash injury criteria limits for female occupants in rear-impact testing.

  • Showed differences in car seat protection performance when using male and female occupant models.

Abstract

Neck injuries sustained in low severity vehicle crashes are of worldwide concern and the risk is higher for females than for males. The objective of the study was to provide guidance on how to evaluate protective performance of vehicle seat designs aiming to reduce the incidence of neck injuries for female and male occupants. The objective was achieved by reviewing injury risk, establishing anthropometric data of an average female, performing dynamic volunteer tests comprising females and males, and developing a finite element model, EvaRID, of an average female. With respect to injury criteria, it was concluded based on the tests that using NIC (with a lower threshold value) and Nkm (with reduced intercept values) for females would be a suitable starting point. Virtual impact simulations with seats showed that differences were found in the response of the BioRID II and EvaRID models, for certain seats.

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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