Effects of child restraint misuse on dynamic performance

The effects of postural support padding modifications to child restraints for children with disability on crash protection

OBJECTIVE

Many children with physical disabilities need additional postural support when sitting and supplementary padding is used on standards approved child restraints to achieve this when traveling in a motor vehicle. However, the effect of this padding on crash protection for a child is unknown. This study aimed to investigate the effect of additional padding for postural support on crash protection for child occupants in forward facing child restraints.

METHODS

Forty frontal sled tests at 49 km/h were conducted to compare Q1 anthropometric test device (ATD) responses in a forward-facing restraint, with and without additional padding in locations to increase recline of the restraint, and/or support the head, trunk and pelvis. Three padding materials were tested: cloth toweling, soft foam, and expanded polystyrene (EPS). The influence of padding on head excursion, peak 3 ms head acceleration, HIC15, peak 3 ms chest acceleration and chest deflection were analyzed.

RESULTS

The influence of padding varied depending on the location of use. Padding used under the restraint to increase the recline angle increased head injury metrics. Toweling in multiple locations which included behind the head increased head excursion and chest injury metrics. There was minimal effect on injury risk measures with additional padding to support the sides of the head or the pelvis position. Rigid EPS foam, as recommended in Australian standards and guidelines, had minimal effect on injury metrics when used inside the restraint, as did tightly rolled or folded toweling secured to the restraint at single locations around the body of the child.

CONCLUSIONS

This study does not support the use of postural support padding to increase recline of a forward-facing restraint or padding behind the head. Recommendations in published standards and guidelines to not use foam that is spongy, soft or easily compressed, with preference for secured firm foam or short-term use of tightly rolled or folded toweling under the child restraint cover is supported. This study also highlights the importance of considering the whole context of child occupant protection when using additional padding, particularly the change in the child's seated position when adding padding in relation to the standard safety features of the restraint.

Child occupant safety in unconventional seating for vehicles with automated driving systems

The objective of this study was to use computational models to study how unconventional seating positions and orientations in vehicles with Automated Driving System (ADS) may affect occupant response metrics of children with various restraint conditions. A literature review was first conducted to frame a simulation plan, including selections of surrogate ADS-equipped vehicles, potential seating arrangements, impact scenarios, anthropomorphic test device (ATD) models, and child restraint system (CRS) models that are relevant to the selected ATD models. Due to the lack of impact tests with child ATDs and CRS in farside, oblique, and rear impacts, 17 sled tests were conducted with CRS harness-restrained ATDs and vehicle belt-restrained ATDs in frontal, farside, oblique, and rear impact conditions. The sled tests were then used to validate a set of MADYMO (MAthematical DYnamic MOdels) v7.7 models. A total of 550 simulations were then conducted with four child ATDs and various CRS conditions across a range of conventional and unconventional seating locations and orientations under five impact directions. We did not find major safety concerns with ATDs restrained by harnessed CRSs based on the nature of ATD contacts. Compared with frontal and rear impacts, CRSs may rotate laterally in farside and oblique impacts, which could result in higher head and chest injury measures than frontal due to inertial loading to the CRS, and the larger lateral rotation of the CRS may lead to a contact between the CRS and vehicle interior. The major safety concern for vehicle belt-restrained ATDs (with and without booster) is that they have the potential to contact the seat next to them or the instrument panel behind them in a farside or oblique impact. Unconventional seating does not necessarily create additional safety concerns beyond what we know with the conventional seating. However, due to the orientation of the unconventional seats, the occupants on those seats may be involved in a higher percentage of oblique and rear-oblique impacts relative to their seating orientations than conventional seats, which may be considered in the future safety design process. This is the first study using different child ATDs and CRSs to investigate child occupant responses in a wide range of impact directions and seating orientations. Results from the sled tests and simulations provide a better understanding of child occupant responses in those crash conditions, but also identified several limitations of using frontal ATDs in other crash directions.

Randomised feasibility trial of a virtual intervention to address infant car seat misuse

BACKGROUND

Serious car seat installation errors occur at high rates in infants and children. These errors significantly increase the risk of child injury in a motor vehicle crash, and few interventions have addressed the challenge longitudinally.

METHODS

This was a pilot randomised controlled feasibility trial of virtual car seat safety checks for caregivers of newborns recruited from an urban newborn nursery. The control (enhanced usual care (EUC)) group received an in-person car seat check as a newborn and virtual check at 9 months. The intervention group received two additional virtual checks at 3 and 6 months. Installation and infant positioning errors were documented and corrected by a child passenger safety technician (CPST). We measured feasibility and acceptability by tracking caregiver and CPST challenges, and caregiver retention. Group differences were tested for statistical significance using χ2 or Fisher's exact test for categorical variables, and two sample t-tests for continuous variables.

RESULTS

33 caregivers were randomised to the EUC and 28 to the intervention group. Virtual checks were feasible, with variable participation levels at each quarter. Wi-Fi and app challenges noted in 30%. There was satisfaction with the virtual car seat checks. At baseline, car seat installation and infant positioning errors occurred at equal frequency, and at 9 months the intervention group had a significantly lower mean proportion than the EUC group in all categories of errors. In summary, virtual seat checks are feasible and the optimal timing of repeat checks requires additional study. A larger study is needed to further evaluate the effect of longitudinal virtual checks on errors.

Comparative performance of rearward and forward-facing child restraint systems with common use errors: Effect on crash injury risk for a 1-year-old occupant

OBJECTIVE

To compare how errors in child restraint use influence crash injury risk in rearward and forward-facing restraints for a 1-year old occupant.

METHODS

Three convertible child restraint systems (CRS) were subjected to frontal dynamic sled tests at 56 km/h in rearward-facing and forward-facing modes in a correct use (baseline) condition and in five incorrect use conditions: loose securing belt, loose harness, partial harness use, top tether slack, and three minor errors. Excursion, head, and chest 3 ms resultant acceleration, HIC15, and neck forces and moments of a Q1 anthropomorphic test device (ATD) seated in the restraints were measured. The effect of incorrect use on each outcome and restraint type was analyzed.

RESULTS

The influence of errors varied across different outcome variables, the three restraints tested and orientation modes. Excursion increased in four of five incorrect use conditions in both rearward and forward-facing orientations. A very loose harness increased four of five outcome variables in at least one forward-facing restraint, whereas only excursion was increased when rearward-facing. Overall, there tended to be a more negative effect of incorrect use (demonstrated through increases in outcome variables compared to the baseline) in the forward-facing orientation.

CONCLUSIONS

Overall, errors in use tended to have a larger negative impact on forward-facing restraints than rearward-facing restraints. Given the widespread nature of errors in use, this adds further weight to arguments to keep children rearward-facing to 12 months of age and older. The results also highlight a variation in response to errors across differently designed restraints, suggesting the influence of errors may be minimized by restraint design that is more resistant to errors.

System providing automated feedback improves task learning outcomes during child restraint system (CRS) installations

OBJECTIVES

The objective was to build and test an automated, interactive educational system to teach adults how to install a child restraint system (CRS) into a vehicle seat.

METHODS

The automated feedback system (AFS) consisted of a mockup vehicle fixture, convertible CRS, and doll. Sensors were implemented into the equipment so that forward-facing (FF) CRS installation errors could be detected. An interactive display monitor guided users through the CRS installation process and alerted them when steps were done incorrectly. Sixty adult volunteers were recruited and randomized into either the treatment group or the control group. The treatment group used the AFS to guide them through a practice installation. The control group also completed a practice installation using the same equipment fixture without the feedback feature turned on; they only had standard printed instruction manuals to guide their tasks. Then, participants from both groups completed a second CRS installation in a real vehicle with standard instruction manuals only. The frequencies and types of errors in all the installations were evaluated by a Child Passenger Safety Technician (CPST). Error rates were compared between the treatment and control groups using lower-tailed t-tests and Pearson's chi-square tests. Error rates were evaluated considering minor and serious errors together and also considering serious errors alone.

RESULTS

Compared to the control group, participants who trained with the AFS exhibited fewer overall errors (minor and serious) in their fixture installations (p < 0.0001) as well as their follow-up vehicle installations (p < 0.0001). Specifically, participants in the treatment group had fewer errors in choosing an installation method, locking the seat belt (SB), tightening the SB or lower anchors (LA), and tightening the harness (p = 0.0002, p = 0.0003, p = 0.0084, and p = 0.0098, respectively, compared to control group during follow-up vehicle installations). The treatment group also performed significantly better than the control group when only serious errors were considered.

CONCLUSIONS

An automated feedback system is an effective way to teach basic CRS installation skills to users.

Restraint Factors and Child Passenger Deaths in New South Wales, Australia

Inappropriate or incorrect use of child restraints can influence crash injury outcome. This study examined the role of restraint factors in child passenger deaths and the effect of legislation requiring appropriate restraint systems up to 7 years old. Data for child (0–12 years) passenger deaths occurring in New South Wales (NSW) from 2007 to 2016 were collected by the child death review team including photographs, reports of in-depth crash investigation, witness reports and medical reports. Restraint use, type of restraint, appropriateness of the restraint for the age of the child and correctness of restraint use were examined. The primary contributor to death was determined in each case. Sixty-four child passengers died in NSW during the data period. Twenty-nine (29/64, 45%) were properly restrained. Thirteen children (13/64, 20%) were unrestrained. In 20 cases (20/64, 31%), children were using a restraint that was either inappropriate for their age (6) or not used correctly (14). Restraint factors were a primary contributor in 22 (22/64, 34%) child deaths. Compared to pre-legislation, appropriate restraint use was more common post-legislation (13/22. 59% vs. 30/42, 71%). However, incorrect use was also greater (3/22, 14% vs. 11/42, 26%). Interventions targeting increasing restraint use and reduction of common ‘use’ errors are needed to prevent further restraint factor-related deaths.