Browse Topic: Child restraint systems
Letter from the Special Issue Editors
This SAE Recommended Practice provides a Glossary of Terms commonly used to describe Seat Belt Restraint Systems Hardware and their function. These terms are currently defined in various SAE Recommended Practices but are sometimes inconsistent. It is intended for this document to supersede the definitions found in separate SAE Recommended Practices.
Many vehicles allow consumers to adapt the vehicle environment to their families’ needs by folding or removing one or more rear row seats. It is currently unclear how different seat configurations affect child restraint systems (CRS) installed in adjacent seats. The objective is to quantify CRS performance in far-side impacts when the seating position adjacent to the CRS is in its normal upright position, folded in half, or removed. Twelve tests were conducted. Second row seats from a recent model year minivan were obtained, including full size captain’s chairs from the outboard positions and narrow seats from the center position. Rear-facing (RF) and forward-facing (FF) CRS were installed one at a time in either the outboard or center position. The seating position adjacent to the CRS was set in either the standard upright position, folded in half, or removed. Far-side impacts were conducted at 10° anterior of pure lateral at 24.8 ± 0.2 g. The Q3s ATD was used for all tests. CRS installed with the adjacent seat removed tended to have the most lateral displacement but lowest HIC36, resultant chest acceleration, and neck loads. Adjacent upright vehicle seats limited the motion of the CRS bases with mid-level level injury metrics. Adjacent folded vehicle seats reduced CRS displacement the most but resulted in higher injury metrics in the head, neck, and chest. When the RF CRS was installed in the narrow center seat with the adjacent (outboard) seat removed, the lower anchor connector of the RF CRS released from the anchor during the impact. This likely occurred due to the narrow seat cushion combined with the shape of the lower anchor hardware. With the exception of this extreme failure, the RF CRS tended to produce lower injury metrics compared to the FF CRS for all corresponding conditions.
Child safety in the back seat during a rear-impact chiefly depends on how well the survival space is maintained at their location. Collapsing front seatback pose a foreseeable hazard as it intrudes into the survival space of the child on the backseat. Furthermore, the condition gets worse in the presence of a structural intrusion from the rear that tends to push the occupant further closer to the backward collapsing seatbacks. This paper reports two real-world rear impact collisions resulting severe to fatal injuries to the child occupant seating behind the driver. Each collision shows the dangers of seatback collapse into the survival space of the child. Furthermore, the paper demonstrates safety through design concept by employing seats with strong seatback design resisting collapse into the survival space of the child. The crash sled-testing are conducted to show the importance of front seatback strength preventing its collapse and occupant ramping up into the child’s survival space. Furthermore, occupant kinematics confirms seatbelt system working together with the seat to increase the level of occupant protection. The shoulder belt limits the shoulder motion and further impedes the occupant ramping up on the seatback. The head, neck and chest injury parameters for the front seat occupants remains below the published Injury Assessment Reference Value (IARV) confirming the advantage of stronger seatbacks in a rear impact scenario protecting rear and front seat occupants.
Child injury performance evaluation is becoming critical part of almost all legal and consumer ratings-based vehicle safety evaluation protocols. Most of New CAR Assessment Programs (NCAP) now have separate ratings exclusively to evaluate child restraint system effectiveness and child dummy performance under various crash testing modes. OEM’s have need and challenge to maximize injury performance. Sled tests are conventionally used for tuning restraints like seat belts and airbags for driver and co-driver under various frontal type test conditions. However, second row seats are used for CRS/ Child injury performance evaluations. In the present study an attempt is made to simulate child injury performance of P3 dummy positioned on second row seat on defined child seat for 64 kmph frontal Offset deformable barrier type test conforming to Global NCAP. Sled pulses are carefully tuned to capture key injury patterns. Thence restraint parameters are tuned to improve child dummy injuries
Side impacts are disproportionately injurious for children compared to other crash directions. Far side impacts allow for substantial translation and rotation of child restraint systems (CRS) because the CRS does not typically interact with any adjacent structures. The goal of this study is to determine whether minor installation incompatibilities between CRS and vehicle seats cause safety issues in far side crashes. Four non-ideal CRS installation conditions were compared against control conditions having good fit. Two repetitions of each condition were run. The conditions tested were: 1) rear-facing (RF) CRS installed with a pool noodle to create proper recline angle, 2) RF CRS with narrow base, 3) forward-facing (FF) CRS with gap behind back near seat bight (i.e., vehicle seat angle too acute for CRS), 4) FF CRS with gap behind back near top of CRS (i.e., vehicle seat angle too obtuse for CRS). Second row captain’s chairs were set up at 10° anterior of lateral. A sled pulse target of 35 kph and 24 g was used. All trials used the Q3s anthropomorphic test device (ATD) with standard instrumentation. CRS were installed using Lower Anchors and Tethers for CHildren (LATCH). The non-ideal RF CRS conditions produced kinetic and kinematic outcomes similar to the RF control trials. All RF trials resulted in the ATD’s head rolling toward the direction of impact along the CRS side wing, although upper neck moments were below injury assessment reference values (IARVs). Non-ideal FF CRS conditions also produced outcomes similar to the FF control trials. The top tether load was higher for the “vehicle seat too acute” condition, although the higher top tether loads did not correlate with higher neck forces or HIC36 values in those trials. Overall, the minor CRS/vehicle incompatibilities examined in this study do not appear to affect the performance of the CRS in the far side impact scenario.
A correctly used child restraint system (CRS) is associated with a substantial reduction of injury and mortality risks in motor vehicle crashes and epidemiologic data suggests that toddlers are provided greater protection when restrained in a rearward-facing CRS compared to a forward-facing CRS. Some ‘extended-use’ European CRS models can accommodate children up to six years rearward-facing and have a support (load) leg and/or a pair of lower (Swedish) tethers to reduce rotation during frontal and rear impacts, respectively. Laboratory studies have found that a support leg reduces head and neck injury metrics of anthropomorphic test devices (ATDs) younger than three years in rearward-facing CRS models during frontal impacts. The objectives of the current study were to perform sled tests to: (1) evaluate the effects of using a support leg in rearward-facing infant and extended-use convertible CRS models during frontal impacts, (2) evaluate the effects of using a pair of lower tethers in a rearward-facing extended-use convertible CRS model during rear impacts and (3) compare responses of ATDs in an extended-use convertible CRS with a support leg and a pair of lower tethers in rearward- and forward-facing configurations during frontal and rear impacts. The presence of a support leg in rearward-facing infant and extended-use convertible CRS models in frontal impacts was associated with reductions in head injury metrics across a range of pediatric ATDs and neck injury metrics were below injury tolerance values. Other strategies in the design of rearward-facing CRS and front row vehicle seatbacks may be available to further reduce head injury metrics. Lower tethers reduced the rearward rotation of an extended-use convertible CRS toward the vehicle seatback in rear impacts and were typically associated with reductions in head and neck injury metrics for the Q6 ATD, but not the Q3 ATD. For frontal impacts, neck injury metrics were typically greater for ATDs in the forward-facing extended-use convertible CRS, whereas head injury metrics were typically greater for the rearward-facing condition (with a support leg and a pair of lower tethers). Interactions of the ATD head and/or the rearward-facing extended-use convertible CRS with the blocker plate in rearward-facing frontal impacts need to be further investigated.
Naturalistic driving studies have shown that pediatric occupants do not assume ideal seating positions in real-world scenarios. Current vehicle assessment programs and child restraint system (CRS) sled tests, such as FMVSS No. 213, do not account for a wide range of seating postures that are typically observed during real-world trips. Therefore, this study aims to analyze the kinematic and kinetic response of a pediatric human body model in various naturalistic seating positions in booster seats when subjected to a frontal offset impact in a full-vehicle environment, with and without the application of pre-crash automatic emergency braking (AEB). A 6YO (seated on a lowback and highback booster) and a 10YO (seated in no-CRS and on a lowback booster) PIPER pediatric human body model’s response was explored in a reference, and two most commonly observed seating postures: forward-leaning and forward-inboard-leaning. The vehicle environment with a side-curtain airbag (SCAB) was subjected to a small offset barrier impact (25% overlap at 40MPH), with and without the application of a pre-crash automatic emergency braking (AEB). 24 conditions were simulated using finite element analysis. Cases with a pre-crash AEB resulted in relatively lower kinematic and kinetic values due to the occupant being in a more flexed position before impact compared to without-AEB cases, coupled with the increased ride-down effect due to AEB. Moreover, different seating postures resulted in substantially different kinematics and kinetics, the injury metrics crossing the injury assessment reference values in some cases. Therefore, to design a passive safety standard test for pediatric occupants, it is important to consider the possible postural changes that may occur.
Current recommendations for restraining child occupants are based on biomechanical testing and data from national and international field studies primarily conducted prior to 2011. We hypothesized that analysis to identify factors associated with pediatric injury in motor-vehicle crashes using a national database of more recent police-reported crashes in the United States involving children under age 13 where type of child restraint system (CRS) is recorded would support previous recommendations. Weighted data were extracted from the National Automotive Sampling System General Estimates System (NASS-GES) for crash years 2010 to 2015. Injury outcomes were grouped as CO (possible and no injury) or KAB (killed, incapacitating injury, non-incapacitating injury). Restraint was characterized as optimal, suboptimal, or unrestrained based on current best practice recommendations. Analysis used survey methods to identify factors associated with injury. Factors with significant effect on pediatric injury risk include restraint type, child age, driver injury, driver alcohol use, seating position, and crash direction. Compared to children using optimal restraint, unrestrained children have 4.9 (13-year-old) to 5.6 (< 1-year-old) times higher odds of injury, while suboptimally restrained children have 1.1 (13-year-old) to 1.9 (< 1-year-old) times higher odds of injury. As indicated by the differences in odds ratios, effects of restraint type attenuate with age. Results support current best practice recommendations to use each stage of child restraint (rear-facing CRS, forward-facing harnessed CRS, belt-positioning booster seat, lap and shoulder belt) as long as possible before switching to the next step.
Abstract - Adult and pediatric human body models have focused on developing accurate representation of the human body in terms of anthropometry and kinetics/kinematics in correlation with published PMHS (Post-Mortem Human Subjects) data. This study focuses on comparing the PIPER 6-year-old human body finite element (FE) model with a Q6 FE model to generate comparable metrics. The FE models were simulated in a vehicle environment by positioning them on two different child booster seats with a 3-point lap-shoulder belt for frontal and lateral impacts. The overall kinematic response (head excursion) of the PIPER human body model (HBM) mimics the behavior of the Q6 ATD. However, there is a significant difference in the NIJ values between the PIPER HBM and Q6 ATD (minimum reduction of 67% in PIPER HBM). The head-neck complex of the PIPER is seen to be more flexible (minimum reduction of 12% in neck forces and 64% in neck moments) as compared to the Q6.
Children tend to be victims of road accidents more often than is the case for adults. Children made up 2,5% of the total number of road fatalities in the EU countries in 2015 and about 15% of the world? population. They are at about a sixth regarding the risk of dying in a road accident of the average member of the population across the EU as a whole.[1] The European Union uses the R44.04 [2] homologation standard to assess child restraint systems (CRS), but in 2013 a new regulation was implemented called Enhanced Child Restraint Systems (ECRS) or UNECE R-129[3] The first step of this regulation, called Phase 1 or I-Size, adds new performance criterion and improved the requirements for the CRS related to safety by introducing side-impact protection, classification based on stature not mass, use of Isofix and mandatory rearward facing until 15 months. Both regulations have been used simultaneously since 2013. In this paper a comparison study was carried out to analyse the differences between both protocols and regulation requirements in order to assess the benefits and impacts of this new standard.
This study examines the performance of rear-facing child restraint systems (RF CRS) in moderate severity rear impact sled tests. The study also investigates the effects of RF CRS features on CRS kinematics and anthropomorphic test device (ATD) injury metrics in this scenario. Twelve tests were conducted at a moderate severity rear impact sled pulse (approximately 28.2 km/h and 18.4 g). Four models of RF CRS were tested in the rear outboard positions of a sedan seat. The CRABI 12-month-old and Hybrid III 3-year-old ATDs were instrumented with head and chest accelerometers, head angular rate sensors, six-axis upper neck load cells, and a chest linear potentiometer (3-year-old only). The effects of carry handle position, occupant size, presence of anti-rebound bar, Swedish style tethering, and lower anchor vs. seat belt installation were investigated. Data were also compared to pediatric injury assessment reference values (IARV). Head Injury Criterion (HIC15) values ranged from 9.6 to 89.2. Chest resultant accelerations (3 ms duration) ranged from 21.3 to 39.9 g. Neck loads and head contact against seat structures varied depending on the features of the CRS. The results indicate that RF CRS mitigate crash forces with a variety of methods in the moderate severity rear impacts performed in this series. This study provides experimental data to address this crash scenario, which are currently lacking in the literature. These conclusions are supported by epidemiological and field data which indicate RF CRS provide good protection for young occupants.
With the market rushing headlong toward trucks, SUVs and crossovers, Volkswagen has badly needed a mid-range SUV between its $25,000 compact Tiguan and $50,000-plus premium Touareg. And now, finally, it has one. Designed and engineered in Wolfsburg, built at VW's billion-dollar Chattanooga plant and riding on the modular MQB platform, the 2018 Atlas ($31,000 base price) enters production three years after the CrossBlue concept made the autoshow rounds. Atlas was developed as “a vehicle to go straight at the heart of the mid-size SUV market,” explained Michael Lovati, Vice President of VW's mid-size/full-size product line.
Oblique crashes to the vehicle front corner may not be characteristic of either frontal or side impacts. This research evaluated occupant response in oblique crashes for a driver, rear adult passenger, and a rear child passenger. Occupant responses and injury potential were evaluated for seating positions as either a far-or near-side occupant. Two crash tests were conducted with a subcompact car. The vehicle’s longitudinal axis was oriented 45 degrees to the direction of travel on a moving platform and pulled into a wall at 56 km/h. Dummies utilized for the seating positions were an adult dummy (50th-percentile-HIII and THOR-Alpha) for the front-left (driver) position, 5th-percentile-female-HIII for the right-rear position, and a 3-year-old HIII for the left-rear position. Test results indicate the driver is at risk of head injury in both conditions and for the far-side position had potential for thoracic/abdominal injuries as the inflatable restraint was not engaged and the occupant slid out of the shoulder belt. The 3-year-old child occupant experienced high neck tension and its head translated beyond the child restraint’s side wings. The small female dummy approached the acceptable limit for the chest acceleration metric in the far-side rear seating position and exceeded the neck IARV in the near side position. Oblique crashes may challenge the sensing and deployment algorithms of restraint control modules, and the resulting occupant kinematics may present a more challenging scenario for occupant protection systems. Ensuring optimal deployment of restraint systems and optimizing restraint performance for oblique occupant motion would likely improve occupant outcomes in oblique impacts.
Passenger car side impact crash tests and sled tests were conducted to investigate the influence of booster seats, near-side occupant characteristics and vehicle interiors on the responses of the Q6/Q6s child ATD positioned in the rear, far-side seating location. Data from nine side impact sled tests simulating a EuroNCAP AEMD barrier test were analyzed with data obtained from 44 side impact crash tests. The crash tests included: FMVSS 214 and IIHS MDB, moving car-to-stationary car and moving car-to-moving car. A Q6 or prototype Q6s ATD was seated on the far-side, using a variety of low and high back booster seats. Head and chest responses were recorded and ATD motions were tracked with high-speed videos. The vehicle lateral accelerations resulting from MDB tests were characterized by a much earlier and more rapid rise to peak than in tests where the bullet was another car. The near-side seating position was occupied by a Hybrid III 10-year-old ATD in the sled tests, and a rear or front facing child restraint or a 5th percentile side impact ATD in the crash tests. Head impacts occurred more frequently in vehicles where a forward facing child restraint was present behind the driver seat for both the low and high back booster seats. Pretensioners were found to reduce lateral head displacements in all sled test configurations but the greatest reduction in lateral excursion was obtained with a high back booster seat secured with LATCH and tested in combination with pretensioners.
Simulation based design optimization has become the common practice in automotive product development. Increasing computer models are developed to simulate various dynamic systems. Before applying these models for product development, model validation needs to be conducted to assess their validity. In model validation, for the purpose of obtaining results successfully, it is vital to select or develop appropriate metrics for specific applications. For dynamic systems, one of the key obstacles of model validation is that most of the responses are functional, such as time history curves. This calls for the development of a metric that can evaluate the differences in terms of phase shift, magnitude and shape, which requires information from both time and frequency domain. And by representing time histories in frequency domain, more intuitive information can be obtained, such as magnitude-frequency and phase-frequency characteristics. However, Most of the existing metrics only focus on time domain. In this paper, a validation method combining analysis in time and frequency domain is proposed. Two analytical cases are then utilized for the illustration of the proposed method and process. A real-world children restraint system design case is then conducted. The evaluation results are consistent with Subjective Matter Experts' judgments.
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