Car Safety for Children Aged 4-12 : real world evaluations of long-term injury outcome, head injury causation scenarios, misuse, and pre-crash maneuver kinematics

Child casualties in car crashes have decreased over the years. Nevertheless, occupant safety in rear seats, especially for children 4-12 years old, needs further attention because motor vehicle crashes remain the leading cause of death and long-term health consequences for children. The aim of this thesis was to obtain comprehensive knowledge of real-life situations for restrained, forward-facing, rear-seated children aged 4-12 years, in frontal car crashes as a basis for vehicle safety improvements to reduce long-term health consequences. The thesis is comprised of four studies based on child-specific data from Sweden and the US. Study I was based on injury data from insurance claim files, covering 2619 injured children in Sweden. Study II was an experimental study of restraint misuse, including 130 Swedish children. Study III analyzed crash data included 27 cases from two US databases, to determine injury causation scenarios. Study IV was a driving study of how pre-crash maneuvers affect child occupant kinematics with 16 children included. The results of Study I emphasized the importance of looking beyond acute, severe injuries and also examine injuries (regardless of initial injury severity) resulting in permanent medical impairment. The vast majority of injuries with the higher degree of permanent medical impairment were severe injuries to the head. The most frequent injuries leading to permanent medical impairment were minor injuries to the neck and head. To reduce the risk of head injuries among children in car crashes, a fundamental step is to ensure that vehicle restraint systems are adapted to the child, physically and behaviorally, and that the child is properly restrained. An experimental study (Study II) of children using integrated booster cushions compared to aftermarket belt positioning booster cushions, showed that misuse related to buckling up, a problem for decades, can be reduced to a minimum by the design of an integrated booster cushion. Minimizing misuse will lead to increases in proper positioning of the restraint on the child and may translate to reductions in head injury risk. Therefore, car manufacturers should focus on integrated booster cushions, preferably as standard equipment. Even with proper use, however, restrained children in rear seats sustained head injuries in frontal impacts by impacting their heads on the side interior and on the seat back in front of them. Oblique impacts and pre-crash steering maneuvers contributed to both these injurycausation scenarios (Study III). Therefore, pre-crash steering maneuvers were further explored in a driving study and it was confirmed that these common pre-crash maneuvers can result in an unstable restraint situation that may potentially compromise rear occupant safety in the event of a crash (Study IV). In conclusion, the primary recommendation as a result of this research is to protect the head and neck of child occupants from both minor and severe injuries, since all severity levels of injuries may result in long-term consequences. Frontal impacts, including oblique impacts or maneuvers prior to impact, need to be addressed to develop “tolerant” restraint systems. Furthermore, it is recommendable to design and use vehicle-built-in restraint systems to improve crash safety among children, by facilitating proper use of the restraint and placement on the child, as has been previously done for front-seated adults. To incentivize vehicle manufacturers to accelerate the implementation of child safety improvements within their vehicles, an assessment of child safety for 4-12-year-old children should be included in consumer rating programs and legal requirements

Safety of children in cars: A review of biomechanical aspects and human body models

The protection of children in motor vehicle crashes has improved since the introduction of child restraint systems. However, motor vehicle crashes remain one of the top leading causes of death for children. Today, computer-aided engineering is an essential part of vehicle development and it is anticipated that safety assessments will increasingly rely on simulations. Therefore, this study presents a review of important biomechanical aspects for the safety of children in cars, including child human body models, for scenarios ranging from on-road driving, emergency maneuvers, and pre-crash events to crash loading. The review is divided into four parts: Crash safety, On-road driving for forward facing children, Numerical whole body models, and Discussion and future outlook.The first two parts provide ample references and a state-of-the-art description of important biomechanical aspects for the safety of children in cars. That children are not small adults has been known for decades and has been considered during the development of current restraints that protect the child in the crash phase. The head, neck, thorax, and pelvis are body areas where development with age changes the biomechanics and the interaction with restraint systems. The rear facing child seat distributes the crash load over a large area of the body and has proved to be a very efficient means of reducing child injuries and fatalities. Children up to age 4. years need to be seated rearward facing for optimal protection, mainly because of the proportionally large head, neck anthropometry and cartilaginous pelvis. Children aged 4 up to 12. years should use a belt positioning booster together with the vehicle seat belt to ensure good protection, as the pelvis is not fully developed and because of the smaller size of these children compared to adults. On-road driving studies have illustrated that children frequently change seated posture and may choose slouched positions that are poor for lap belt interaction if seated directly on the rear seat. Emergency maneuvers with volunteers illustrate that pre-crash loading forces forward-facing children into involuntary postures with large head displacements, having potential influence on the risk of head impact. Children, similar to adults, benefit from the safety systems offered in the vehicle. By providing child adaptability of the vehicle, such as integrated booster cushions, the child-restraint interaction can be further optimized. An example of this is the significant reduction of lap belt misuse when using integrated boosters, due to the simplified and natural positioning of the lap belt in close contact with the pelvis. The research presented in this review illustrates that there is a need for enhanced tools, such as child human body models, to take into account the requirements of children of different ages and sizes in the development of countermeasures.To study how children interact with restraints during on-road driving and during pre- and in-crash events, numerical child models implementing age-specific anthropometric features will be essential. The review of human whole body models covers multi body models (age 1.5 to 15. years) and finite element models (ages 3, 6, and 10. years). All reviewed child models are developed for crash scenarios. The only finite element models to implement age dependent anthropometry details for the spine and pelvis were a 3. year-old model and an upcoming 10. year-old model. One ongoing project is implementing active muscles response in a 6. year-old multi body model to study pre-crash scenarios. These active models are suitable for the next important step in providing the automotive industry with adequate tools for development and assessment of future restraint systems in the full sequence of events from pre- to in-crash. Document type: Articl

REAR SEAT SAFETY IN FRONTAL TO SIDE IMPACTS – FOCUSING ON OCCUPANTS FROM 3YRS TO SMALL ADULTS

ABSTRACT This study presents a broad comprehensive research effort that combines expertise from industry and academia and uses various methodologies with applied research directed towards countermeasures. The project includes real world crash data analysis, real world driving studies and crash testing and simulations, aiming at enhancing the safety of forward facing child occupants (aged 3y to small adults) in the rear seat during frontal to side impacts. The real world crash data analyses of properly restrained children originate from European as well as US data. Frontal and side impact crash tests are analyzed using different sizes of crash test dummies in different sitting postures. Side impact parameter studies using FE-models are run. The sitting posture and behavior of 12 children are monitored while riding in the rear seat. Also, the body kinematics and belt position during actual braking and turning maneuvers are studied for 16 rear seat child occupants and for various child dummies. Real world crash data indicates that several of the injured children in frontal impacts, despite being properly restrained, impacted the vehicle interior structure with their head/face resulting in serious injury. This was attributed to oblique crashes, pre-crash vehicle maneuvers or high crash severity. Crash tests confirm the importance of proper initial belt-fit for best protection. The crash tests also highlight the difficulty in obtaining the real world kinematics and head impact locations using existing crashtest dummies and test procedures. The side impact parameter studies indicate that the vehicle’s occupant protection systems, such as airbags and seat belt pretensioners, play an important role in protecting children as well. The results from the on-road driving studies illustrate the variation of sitting postures during riding in the rear seat giving valuable input to the effects of the restraint systems and to how representative the standardized dummy seating positioning procedures are. The results from the maneuver driving studies illustrate the importance of understanding the kinematics of a child relative to the seat belt in a real world maneuver situation. Real world safety of rear seat occupants, especially children, involves evaluation of protection beyond standard crash testing scenarios in frontal and side impact conditions. This project explores the complete context of rear seat protection in impact situations ranging from front to side and directions in between highlighting the importance of pre-crash posture and behavior. This research project at SAFER (Vehicle and Traffic Safety Centre at Chalmers), where researchers from the industry and universities cooperate with the aim to further improve safety for children (from 3y) to small adults in the rear seat, speeds up the process to safety implementation due to the interaction between academic and industrial researchers

New molecular methods to assess biodiversity. Potentials and pitfalls of DNA metabarcoding: a workshop report

This report presents the outcome of the joint work of PhD students and senior researchers working with DNA-based biodiversity assessment approaches with the goal to facilitate others the access to definitions and explanations about novel DNA-based methods. The work was performed during a PhD course (SLU PNS0169) at the Swedish University of Agricultural Sciences (SLU) in Uppsala, Sweden. The course was co-organized by the EU COST research network DNAqua-Net and the SLU Research Schools Focus on Soils and Water (FoSW) and Ecology - basics and applications. DNAqua-Net (COST Action CA15219, 2016-2020) is a network connecting researchers, water managers, politicians and other stakeholders with the aim to develop new genetic tools for bioassessment of aquatic ecosystems in Europe and beyond. The PhD course offered a comprehensive overview of the paradigm shift from traditional morphology-based species identification to novel identification approaches based on molecular markers. We covered the use of molecular tools in both basic research and applied use with a focus on aquatic ecosystem assessment, from species collection to the use of diversity in environmental legislation. The focus of the course was on DNA (meta)barcoding and aquatic organisms. The knowledge gained was shared with the general public by creating Wikipedia pages and through this collaborative Open Access publication, co-authored by all course participants

Misuse of Booster Cushions – An Observation Study of Children’s Performance during Buckling Up

Booster cushions are effective tools to protect children from injuries in car crashes, but there remains a large amount of misuse. The aim of this study was to assess potential misuse of booster cushions in an observational laboratory study, and to identify whether booster cushion design, age or clothing had any effect. 130 Swedish children from the ages of 4–12 years participated. Each child buckled up on an integrated and on an aftermarket booster cushion in the rear seat. The older children also buckled up with seat belt only. Interviews, observations and body measurements were performed. Time to buckle up and amount of belt slack were registered. Photographs were taken to document misuse. Results showed that 77% failed to perform correct belt routing on the aftermarket cushion, independent of age, although they were familiar with this system. The misuse rate for the integrated cushion was only 4%. No misuse was found for seat belt only. Few children tightened the belt. The belt slack increased when wearing winter jackets. This indicates the importance of adding pretensioners to the rear seat. Sled tests with HIII&TNO 6y dummies were also performed for the most frequent misuse situations found. The main conclusion is that an integrated booster cushion has many advantages compared to an aftermarket cushion regarding both safety and comfort. It is easy and quick to handle, has few possibilities for misuse, has an intuitive design, the buckling up sequence is equal to buckling up with an ordinary seat belt, and younger children can buckle up correctly

Rear-End Impact Assessment expanded with Pre-Impact Posture Variations

Present whiplash injury assessment tests, reflecting the seat performance only, provide limited insights into real-world whiplash injury protection needs. Virtual testing of braking followed by a rear-end impact, in addition to alternative initial sitting postures, were conducted to investigate if the current anthropomorphic test device can be used to cover a larger scope of the real-world context. Reconstruction of published 1.1 g braking volunteer tests showed that a BioRID FE model was capable of recreating human-like kinematics; with head and T1 kinematics just within a 1 SD corridor on the low side of the volunteer response, while vertical displacements and lap-belt forces were underpredicted. A simulation series including pre-impact braking prior to rear-end impact investigated two strategies to vary the backset, as well as pre-impact means of intervention, exemplified by pre-impact seatbelt pretensioning. Using virtual testing, the study demonstrates examples of expanding the whiplash assessment test setup, enabling inclusion of a variety of occupant sitting postures and a braking event preceding the rear-end impact, while still being feasible to execute. As a next step, a human body model capable of seamless pre-crash and crash prediction could even allow for more in-depth investigations, as well as inclusion of ranges of occupant sizes and posture setting possibilities

Pretensioner Loading to Rear-Seat Occupants During Static and Dynamic Testing

<div><p><b>Objective:</b> Pretensioners reduce the seat belt slack and couple the occupant early to the restraint system. There is a growing prevalence of rear seat pretensioners and it is essential to determine whether the load from the pretensioner itself can cause injuries to rear-seated children. The aim of the study was to investigate the loading to the neck, chest, and abdomen of various sizes of anthropometric test devices (ATDs) during the pretensioner deployment phase and the crash phase in low-severity frontal sled tests and during static deployment.</p><p><b>Methods:</b> Low-severity frontal sled tests were conducted with the Hybrid III (HIII) 3-year-old, HIII 6-year-old, HIII 5th percentile, and HIII 50th percentile ATDs. Two different retractor pretensioners with varying pretensioner force were used. The child ATDs were restrained on a booster cushion (BC), with and without a back. The loading to the neck and chest was compared to injury assessment reference values (IARVs) reported by Mertz et al. (2003). The chest loading to the HIII 5th percentile and HIII 50th percentile ATDs was also analyzed using age-related injury risk curves. Static pretensioner tests with the Q-series 10-year-old ATD, equipped with an advanced abdominal loading device, were conducted in standard ATD position and out-of-position with the lap belt positioned high on the abdomen.</p><p><b>Results:</b> During the crash phase, head excursion and neck loading were reduced for both pretensioners for all ATDs compared to testing without a pretensioner. The pretensioner reduced chest deflection to the adult ATDs but not to child ATDs when seated on a BC with a back during the crash phase. When the back was removed, chest deflection was reduced below IARV. The head excursion was reduced for all ATDs with both pretensioners.</p><p>During the pretensioner deployment phase, the chest deflection exceeded the IARV for the HIII 3-year-old with the stronger pretensioner when seated on booster with a back and it was reduced below the IARV with the lower force pretensioner. For all ATDs, neck and chest loading during the pretensioner deployment phase were reduced when a pretensioner with lower force was used.</p><p>Abdominal loading to the Q10 in the static pretensioner deployments indicated a low risk of abdominal injury in all tested positions.</p><p><b>Conclusion:</b> This study indicates the need to balance the pretensioner force and seat belt geometry to gain good pretensioner performance in both the pretensioner deployment phase and the crash phase.</p></div

Head injury criteria assessment using head kinematics from crash tests and accident reconstructions

Objective: The aim of this study was to assess head injury criteria based on their correlation to brain strain in a Finite Element (FE) head model (the KTH Royal Institute of Technology model), by simulation of head kinematics data from frontal and side crash tests with Anthropomorphic Test Devices (ATDs), and from Human Body Model (HBM) accident reconstructions. Methods: Six Degrees of Freedom (DoF) head kinematic data was extracted from 221 crash tests, consisting of frontal impacts with the THOR-50M ATD, near-side and far-side impacts with the WorldSID-50M ATD, and from 19 FE HBM accident reconstructions. The head injury criteria HIC15, HIP, BrIC, UBrIC, DAMAGE and CIBIC were calculated, and FE head model simulations were conducted using the six DoF kinematics data. The 100th, 99th, and 95th percentile Maximum Principal Strains (MPS) of the brain were extracted and linear regression models with respect to the injury criteria were created. The injury criteria were then evaluated based on the coefficient of determination, R2, and the Normalized Root Mean Square Error (NRMSE) of each regression model. Results: For all the data sets combined and for the WorldSID far-side data, CIBIC had the best goodness of fit, with R2 of 0.76 and 0.85. For frontal impacts with THOR and the combined ATD data set, DAMAGE had highest R2, 0.83 and 0.78, respectively. Injury criteria including translational accelerations were ranked lower, and BrIC were among the three lowest ranked for most data sets evaluated. UBrIC generally ranked after DAMAGE and CIBIC with respect to the goodness of fit but had the lowest NRMSE for all data sets. Conclusions: The two mass-spring-damper brain surrogate model criteria, DAMAGE and CIBIC, were best in capturing the head model MPS response for both the THOR and WorldSID data sets. BrIC had lower correlation to the head model MPS and performed marginally better than the linear acceleration only criteria for all the data sets combined. This study supports the suitability of DAMAGE and CIBIC as brain injury criteria to be used with THOR-50M and WorldSID-50M in vehicle crash test conditions, as they outperform BrIC