Forward-facing Child Restraint System Research Articles

Key factors associated with child occupants’ suboptimal head positions when travelling in child restraint systems: Results from a naturalistic driving study of children in cars

ObjectiveThe current study aimed to quantify the real-world, everyday travel behaviours of child vehicle occupants and associations with child restraint systems (CRS)/booster seat (BS) head positions that are suboptimal in terms of crash injury risk. MethodsThe data from a naturalistic driving study (NDS) provided 414 trips for analysis. Child occupant behaviour, head position within their forward-facing CRS (FFCRS) or BS and other relevant information was coded for nine discrete 5 s intervals or ‘epochs’ (5%, 17%, 25%, 30%, 50%, 53%, 75%, 89% & 95% of trip duration). A total of 2158 epochs were analysed. The relative contributions of factors of interest to suboptimal head position were explored through a generalised estimating equation (GEE), which accommodated correlation between measurement in each epoch for an individual child. ResultsThe GEE revealed that, when compared to child occupants travelling in a FFCRS, child occupants travelling in a BS were twice as likely to have a suboptimal head position. Child occupants were also nearly one and a half times more likely to have a suboptimal head position if they were in the older age range for the restraint type that they were using (FFCRS or BS), if they had incorrect shoulder belt/harness use, or if they were interacting with other vehicle occupants. In addition, when compared to engagement in conversation, children's engagement in a lap-based activity (including use of electronic devices, toys and reading) increased the odds of suboptimal head position by nearly two and half times,. ConclusionsThis study identified key factors associated with child occupants’ head positions when travelling in a CRS. These findings suggest that various head positions are adopted during everyday travel. Future restraint and vehicle designs that improve the ability of child occupant protection systems (CRS and vehicle-based devices) to safely accommodate a wide range of suboptimal head positions that were commonly observed during everyday travel are encouraged.

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.

Evaluation of Rotation Reduction Features in Infant and Extended-Use Convertible Child Restraint Systems during Frontal and Rear Impacts.

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 extendeduse 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.

The effect of chin-to-chest contact on upper neck axial force in UN Regulation No. 129 frontal impact tests of child restraint systems

Objective The objective of this study was to investigate the effect of chin-to-chest contact on upper neck axial force in United Nations (UN) Regulation No. 129 frontal impact tests of child restraint systems. Methods Frontal impact pilot experiments were carried out according to the test procedure in UN Regulation No. 129. Q-Series child dummies were seated in a small convenience sample of forward-facing child restraint systems. The timing and duration of chin-to-chest contact were determined using the procedure for calculating external head impact force in SAE J2052. Results Chin-to-chest contact was observed in all of our experiments and generated a tensile peak in the upper neck axial force of the Q-Series dummies. Prior to chin-to-chest contact, a purely inertial, noncontact peak was observed in the axial tension force. The tensile peak due to chin-to-chest contact was often greater than the inertial, noncontact peak force. Conclusions Chin-to-chest contact can increase axial neck tension force beyond the level it would reach under purely inertial loading. Adopting upper neck axial force in regulation, without considering how the force is generated, might encourage child restraint designs that mitigate only chin-to-chest contact, rather than the true inertial neck loading.

The Roles of Vehicle Seat Cushion Stiffness and Length in Child Restraint System (CRS) Performance

<div class="section abstract"><div class="htmlview paragraph">The objective is to determine whether responses and injury risks for pediatric occupants in child restraint systems (CRS) are affected by vehicle seat cushion stiffness and fore/aft cushion length. Eighteen sled tests were conducted using the Federal Motor Vehicles Safety Standard (FMVSS) 213 frontal pulse (48 km/h). Seats from a recent model year vehicle were customized by the manufacturer with three different levels of cushion stiffness: compliant, mid-range, and stiff. Each stiffness level was quantified using ASTM D 3574-08 and all were within the realistic range of modern production seats. The usable length of each seat cushion was manipulated using foam spacers provided by the manufacturer. Two different seat lengths were examined: short (34.0 cm) and long (43.5 cm). Three different types of CRS were tested with size-appropriate anthropomorphic test devices (ATDs): rear-facing (RF) CRS with 12-month-old CRABI, forward-facing (FF) CRS with Hybrid III 3-year-old, and high-back booster with Hybrid III 6-year-old. Each CRS, vehicle seat (including cushion and frame), seat belt webbing and buckle were replaced after every test. ATD kinematic and kinetic data were compared across seat cushion lengths and cushion stiffness levels to determine which seat configurations were the most beneficial for each type of CRS. For RF CRS, short vehicle seats allowed more y-axis rotation (SAE J211) but reduced several injury metrics including HIC36. For FF CRS, long and short seats resulted in similar injury metrics across matched conditions. For boosters, short seats increased chest resultant acceleration but did not have a noticeable effect on other injury metrics. The range of cushion stiffness examined in this study did not have a consistent or relevant effect on any of the CRS or occupant responses.</div></div>

The common characteristics and behaviors of child occupants in motor vehicle travel

Objective: Child occupant behavior and head position when travelling in child restraint systems (CRS) may have an effect on injury risk in the event of a motor vehicle crash. The current study aimed to describe the common characteristics and behaviors of child occupants during everyday, real-world motor vehicle travel in a sample of Australian families to identify potential safety implications of observed behaviors and head position within the CRS.Methods: Two instrumented study vehicles were used by 42 families for approximately two weeks. Continuous video and audio data were collected across 1,651 trips (over 600 hours). An online survey provided additional parent, familial and child occupant data. The characteristics and behaviors of 72 child occupants (aged 14 months to 9 years) who travelled in a forward-facing CRS (FFCRS) or a belt-positioning booster seat (BS) were observed and recorded by manual review of a sample of the video/audio recordings. One quarter of all trips (n = 414) was randomly selected for coding/analysis and, within each trip, one child occupant was selected who was travelling in a FFCRS or BS. Child occupant behaviors, head position within the FFCRS or BS, and other relevant information was coded for each trip during nine discrete five second intervals or ‘epochs’ (5%, 17%, 25%, 30%, 50%, 53%, 75%, 89% and 95% of trip duration).Results: In the majority of epochs (74%), child occupants’ heads were observed to be ‘optimally’ positioned within the FFCRS or BS. For more than half of the epochs, child occupants were observed to be: correctly restrained (58%) and involved in an interaction with another vehicle occupant (59%). Bivariate analyses revealed that children travelling in a FFCRS were significantly more likely to be observed to have optimal head positions than those travelling in a BS (78% vs. 62%), χ2 (1) = 86.00, p < 0.001. Child occupants who were observed to be ‘correctly’ restrained were significantly more likely to be observed to have optimal head positions than those who were observed to be ‘incorrectly’ restrained (80% vs. 20%), χ2 (1) = 10.33, p < 0.01.Conclusions: This is the first naturalistic driving study (NDS) to specifically explore the factors associated with child occupants’ head position when travelling in a CRS. Findings from the current study can be used to inform the positioning of anthropometric test dummies (ATD) in CRS testing, guide improvements to CRS/vehicle design, and develop targeted educational strategies to improve child occupant safety.

The influence of child restraint lower attachment method on protection offered by forward facing child restraint systems in oblique loading conditions

ABSTRACTObjective: The research objective was to quantify the influence of child restraint lower attachment method on head kinematics, head impact potential, and head, neck, and thorax injury metrics for a child occupant secured in a forward-facing child restraint system (FFCRS) in oblique side impacts.Methods: Fifteen sled tests were conducted with a Q3s seated in an FFCRS secured to the center position on a production small SUV bench seat. Three lower attachment methods were evaluated: rigid ISOFIX, a flexible single loop lower anchors and tethers for children (LATCH) webbing routed through the vehicle belt path of the FFCRS, and dual flexible LATCH webbing attachments on either side of the FFCRS. All were tested with and without a tether with one repeat test in each test condition. The same model FFCRS was used for all tests; only the attachment method varied. The vehicle bench seat was fixed on the sled carriage at 80° (from full frontal). The input pulse was the proposed FMVSS 213 side impact pulse scaled to a 35 km/h delta-v. Two-way analysis of variance (ANOVA) was used to evaluate the effect of lower attachment and tether use on 3 outcome metrics: lateral head excursion, neck tension, and neck lateral bending. Data included anthropomorphic test dummy (ATD) head excursions, head linear accelerations and angular velocities, neck loads and moments, thoracic accelerations, lateral chest deflections, lower anchor loads, and tether webbing loads. ATD head kinematics were collected from 3-dimensional motion capture cameras.Results: Results demonstrated a reduction in injury measures with the rigid ISOFIX and dual webbing attachment compared to the single webbing attachment with decreased lateral head excursions (331, 356, and 441 mm for the rigid ISOFIX, dual webbing, and single webbing systems, respectively, P <.0001), neck tension (1.4, 1.6, and 2.2 kN, P <.01), and neck lateral bending (31.8, 38.7, and 38.0 Nm, P =.002). The tether had a greater influence on lateral head excursion for the FFCRS with flexible webbing attachments than those with the rigid attachment, with the tether forces being highest with the single webbing attachment. Lateral head excursions were significantly lower and lateral neck bending moments were significantly higher with tether use (P <.0001) across all lower attachments. The effect of tether on neck tension was mixed, only showing an increased effect with the rigid ISOFIX system.Conclusion: The CRS lower attachment system influenced occupant kinetics. The results indicate that CRS attached to the vehicle via rigid and dual webbing systems exhibit improved kinematics by reducing the rotation and tipping seen with the single webbing attachment. This leads to reduced lateral head excursions and neck tension values. The advantages of the tether in reducing lateral head excursion in side impacts are most pronounced with the flexible webbing attachments. With tether use low in the United States, a dual webbing type FFCRS attachment system may be a better attachment method than single webbing and provide a simpler engineering solution than rigid ISOFIX attachment.

Rear-facing versus forward-facing child restraints: an updated assessment

ObjectivesThe National Highway Traffic Safety Administration and the American Academy of Pediatrics recommend children be placed in rear-facing child restraint systems (RFCRS) until at least age 2. These recommendations are...

Caregivers’ Use of Child Passenger Safety Resources and Quality of Future Child Restraint System Installations

Objectives: Child Restraint System (CRS) misuse is common. We characterized caregivers’ use of child passenger safety informational and instructional resources and determined whether there were differences in the quality of CRS installations associated with prior exposure to specific resources as evaluated in a standardized CRS installation environment. Methods: Caregivers completed self-report surveys and installed a forward-facing CRS in a controlled environment. Installations were evaluated for security (tightness) and accuracy (no errors) by a child passenger safety technician (CPST). Results: CRS manuals were the most common way caregivers learned to install a CRS. Primary care providers (PCP)s were the most frequently endorsed source of CRS safety information. There was no strong pattern of associations between prior exposure to resources and installation quality (security or accuracy), although some evidence supports protective effects of learning from CPSTs; 13% (19 out of 151) installations were secure and 57% (86 out of 151) installations were accurate. Conclusions: A focus on developing effective and lasting behavioral interventions is needed.

Differences in the kinematics of booster-seated pediatric occupants using two different car seats

ABSTRACTObjective: The objective of this article is to compare the performance of forward-facing child restraint systems (CRS) mounted on 2 different seats.Methods: Two different anthropomorphic test device (ATD) sizes (P3 and P6), using the same child restraint system (a non-ISOFIX high-back booster seat), were exposed to the ECE R44 regulatory deceleration pulse in a deceleration sled. Two different seats (seat A, seat B) were used. Three repetitions per ATD and mounting seat were done, resulting in a total of 12 sled crashes. Dummy sensors measured the head tri-axial acceleration and angular rate and the thorax tri-axial acceleration, all acquired at 10,000 Hz. A high-speed video camera recorded the impact at 1,000 frames per second. The 3D kinematics of the head and torso of the ATDs were captured using a high-speed motion capture system (1,000 Hz). A pair-matched statistical analysis compared the outcomes of the tests using the 2 different seats.Results: Statistically significant differences in the kinematic response of the ATDs associated with the type of seat were observed. The maximum 3 ms peak of the resultant head acceleration was higher on seat A for the P3 dummy (54.5 ± 1.9 g vs. 44.2 ± 0.5 g; P =.012) and for the P6 dummy (56.0 ± 0.8 g vs. 51.7 ± 1.2 g; P =.015). The peak belt force was higher on seat A than on seat B for the P3 dummy (5,488.0 ± 198.0 N vs. 4,160.6 ± 63.6 N; P =.008) and for the P6 dummy (7,014.0 ± 271.0 N vs. 5,719.3 ± 37.4 N; P =.015). The trajectory of the ATD head was different between the 2 seats in the sagittal, transverse, and frontal planes.Conclusion: The results suggest that the overall response of the booster-seated occupant exposed to the same impact conditions was different depending on the seat used regardless of the size of the ATD. The differences observed in the response of the occupants between the 2 seats can be attributed to the differences in cushion stiffness, seat pan geometry, and belt geometry. However, these results were obtained for 2 particular seat models and a specific CRS and therefore cannot be directly extrapolated to the generality of vehicle seats and CRS.

Has Child Restraint System Use Increased among Parents of Children in Shantou, China?

Objective: to examine parents’ use of child restraint systems (CRS), and determine if parents’ knowledge of, attitude toward, and use behavior of child restraint systems have improved following enactment of child restraint use laws in other cities. Design: Observations and a cross-sectional survey of drivers transporting children 17 years and under were conducted at the gate of the schools and parking lots of hospitals in Shantou. Observers recorded the seating location of child passengers, the type of restraint, and appropriate use of CRS and safety belts based on the observation. Knowledge of and attitudes towards use of CRS were reported by the driver following observation. Results: Approximately 6.6% of passengers aged 0–12 were in CRS; rate of forward-facing CRS in children aged 3–5 (9.9%) was higher than rear-facing CRS for children aged 0–2 (1.1%) and booster seat use among children aged 6–12 (0.1%). Children younger than four years old (OR = 3.395, 95% CI = 2.125–5.424), drivers having a college or higher lever education (OR = 2.908, 95% CI = 1.878–4.500) and drivers wearing seatbelt (OR = 3.194, 95% CI = 1.605–6.356) had greater odds of CRS use. Over half (56.6%) of parents might or would use CRS if they could rent CRSs with fees. Conclusions: The rate of CRS is still low in Shantou. Comprehensive public education programs supported by legislation might be an effective way to improve child passenger safety. Renting CRSs to parents could be a new approach to encourage use.

Protection of children in forward-facing child restraint systems during oblique side impact sled tests: Intrusion and tether effects

ABSTRACTObjective: Testing was conducted to quantify the kinematics, potential for head impact, and influence on head injury metrics for a center-seated Q3s in a forward-facing child restraint system (FFCRS) in oblique impacts. The influences of a tether and intruded door on these measures were explored.Methods: Nine lateral oblique sled tests were conducted on a convertible forward-facing child restraint seat (FFCRS). The FFCRSs were secured to a bench seat from a popular production small SUV at the center seating position utilizing the lower anchor and tether for children (LATCH). The vehicle seat was fixed on the sled carriage at 60° and 80° from full frontal (30° and 10° forward rotation from pure lateral) providing an oblique lateral acceleration to the Q3s and FFCRS. A structure simulating an intruded door was mounted to the near (left) side of vehicle seat. The sled input acceleration was the proposed FMVSS 213 lateral pulse scaled to a 35 km/h delta-V. Tests were conducted with and without the tether attached to the FFCRS.Results: Results indicate the influence of the tether on kinematics and injury measures in oblique side impact crashes for a center- or far-side-seated child occupant. All tests without a tether resulted in head contact with the simulated door, and 2 tests at the less oblique angle (80°) with a tether also resulted in head contact. No head-to-door contact was observed in 2 tests utilizing a tether. High-speed video analysis showed that the head moved beyond the CRS head side wings and made contact with the simulated intruded door. Head injury criterion (HIC) 15 median values were 589 without the tether vs. 332 with the tether attached. Tests utilizing a tether had less lateral head excursion than tests without a tether (median 400 vs. 442 mm).Conclusion: These tests demonstrate the important role of the tether in controlling head excursion for center- or far-side-seated child occupants in oblique side impact crashes and limiting the head injury potential with an intruded door. The tether may not influence the kinematics of a near-side-seated occupant as strongly where the vehicle door or side structure interacts with the CRS and influences its motion. The results indicate that there may be an opportunity to improve child head kinematics and head protection in oblique side impacts through different CRS attachment methods and/or alternative vehicle side structure protection or padding.

Naturalistic driving study of rear seat child occupants: Quantification of head position using a Kinect™ sensor

ABSTRACTObjective: Restraint performance is evaluated using anthropomorphic test devices (ATDs) positioned in prescribed, optimal seating positions. Anecdotally, humans—children in particular—assume a variety of positions that may affect restraint performance. Naturalistic driving studies (NDSs), where cameras and other data acquisition systems are placed in a vehicle used by participants during their regular transportation, offer means to collect these data. To date, these studies have used conventional video and analysis methods and, thus, analyses have largely been qualitative. This article describes a recently completed NDS of child occupants in which their position was monitored using a Kinect sensor to quantify their head position throughout normal, everyday driving trips.Methods: A study vehicle was instrumented with a data acquisition system to measure vehicle dynamics, a set of video cameras, and a Kinect sensor providing 3D motion capture at 1 Hz of the rear seat occupants. Participant families used the vehicle for all driving trips over 2 weeks. The child occupants' head position was manually identified via custom software from each Kinect color image. The 3D head position was then extracted and its distribution summarized by seat position (left, rear, center) and restraint type (forward-facing child restraint system [FFCRS], booster seat, seat belt).Results: Data from 18 families (37 child occupants) resulted in 582 trips (with children) for analysis. The average age of the child occupants was 45.6 months and 51% were male. Twenty-five child occupants were restrained in FFCRS, 9 in booster seats, and 3 in seat belts. As restraint type moved from more to less restraint (FFCRS to booster seat to seat belt), the range of fore–aft head position increased: 218, 244, and 340 mm on average, respectively. This observation was also true for left–right movement for every seat position. In general, those in the center seat position demonstrated a smaller range of head positions.Conclusions: For the first time in a naturalistic setting, the range of head positions for child occupants was quantified. More variability was observed for those restrained in booster seats and seat belts than for those in FFCRS. The role of activities, in particular interactions with electronic devices, on head position was notable; this will be the subject of further analysis in other components of the broader study. These data can lead to solutions for optimal protection for occupants who assume positions that differ from prescribed, optimal testing positions.

The Influence of Enhanced Side Impact Protection on Kinematics and Injury Measures of Far- or Center-Seated Children in Forward-Facing Child Restraints

Objective: To evaluate the influence of forward-facing child restraint systems’ (FFCRSs) side impact structure, such as side wings, on the head kinematics and response of a restrained, far- or center-seated 3-year-old anthropomorphic test device (ATD) in oblique sled tests.Methods: Sled tests were conducted utilizing an FFCRS with large side wings and with the side wings removed. The CRS were attached via LATCH on 2 different vehicle seat fixtures—a small SUV rear bench seat and minivan rear bucket seat—secured to the sled carriage at 20° from lateral. Four tests were conducted on each vehicle seat fixture, 2 for each FFCRS configuration. A Q3s dummy was positioned in FFCRS according to the CRS owner's manual and FMVSS 213 procedures. The tests were conducted using the proposed FMVSS 213 side impact pulse. Three-dimensional motion cameras collected head excursion data. Relevant data collected during testing included the ATD head excursions, head accelerations, LATCH belt loads, and neck loads.Results: Results indicate that side wings have little influence on head excursions and ATD response. The median lateral head excursion was 435 mm with side wings and 443 mm without side wings. The primary differences in head response were observed between the 2 vehicle seat fixtures due to the vehicle seat head restraint design. The bench seat integrated head restraint forced a tether routing path over the head restraint. Due to the lateral crash forces, the tether moved laterally off the head restraint reducing tension and increasing head excursion (477 mm median). In contrast, when the tether was routed through the bucket seat's adjustable head restraint, it maintained a tight attachment and helped control head excursion (393 mm median).Conclusion: This testing illustrated relevant side impact crash circumstances where side wings do not provide the desired head containment for a 3-year-old ATD seated far-side or center in FFCRS. The head appears to roll out of the FFCRS even in the presence of side wings, which may expose the occupant to potential head impact injuries. We postulate that in a center or far-side seating configuration, the absence of door structure immediately adjacent to the CRS facilitates the rotation and tipping of the FFCRS toward the impact side and the roll-out of the head around the side wing structure. Results suggest that other prevention measures, in the form of alternative side impact structure design, FFCRS vehicle attachment, or shared protection between the FFCRS and the vehicle, may be necessary to protect children in oblique side impact crashes.

Investigation of Child Restraint System (CRS) Compatibility in the Vehicle Seat Environment

Objective: Child restraint system (CRS) misuse is common and can have serious consequences to child safety. Physical incompatibilities between CRS and vehicles can complicate the installation process and may worsen CRS misuse rates. This study aims to identify the most common sources of incompatibility between representative groups of CRS and vehicles.Methods: Detailed dimensional data were collected from 59 currently marketed CRS and 61 late model vehicles. Key dimensions were compared across all 3,599 theoretical CRS/vehicle combinations and the most common predicted incompatibilities were determined. A subset of 34 physical installations was analyzed to validate the results.Results: Only 58.2% of rear-facing (RF) CRS/vehicle combinations were predicted to have proper agreement between the vehicle's seat pan angle and the CRS manufacturers’ required base angle. The width of the base of the CRS was predicted to fit snugly between the vehicle's seat pan bolsters in 63.3% of RF CRS/vehicle combinations and 62.2% of forward-facing (FF) CRS/vehicle combinations. FF CRS were predicted to be free of interaction with the vehicle's head restraint in 66.4% of combinations. Roughly 90.0% of RF CRS/vehicle combinations were predicted to have enough horizontal clearance space to set the front seat in the middle its fore/aft slider track. Compatibility rates were above 98% regarding the length of the CRS base compared to the length of the vehicle seat pan and the ability of the top tether to reach the tether anchor. Validation studies revealed that the predictions of RF CRS base angle range vs. seat pan angle compatibility were accurate within 6%, and head restraint interference and front row clearance incompatibilities may be more common than the dimensional analysis approach has predicted.Conclusions: The results of this study indicate that RF CRS base angles and front row clearance space, as well as FF CRS head restraint interference, are frequent compatibility concerns. These results enable manufacturers, researchers, and consumers to focus their attention on the most relevant CRS/vehicle incompatibility issues in today's market.

Evaluation of ISO CRS Envelopes Relative to U.S. Vehicles and Child Restraint Systems

Objectives: The objectives of this study are to use computer simulation to evaluate the International Organization for Standardization (ISO) 13216-3:2006(E) child restraint system (CRS) envelopes relative to rear seat compartments from vehicles and CRSs in the U.S. market, investigate the potential compatibility issues of U.S. vehicles and CRSs, and demonstrate whether necessary modifications can be made to introduce such a system into compatibility evaluations between U.S. vehicles and CRSs.Methods: Three-dimensional geometry models for 26 vehicles and 16 convertible CRS designs developed previously were used. Geometry models of 3 forward-facing and 3 rear-facing CRS envelopes provided by the ISO were built in the current study. The virtual fit process closely followed the physical procedures described in the ISO standards.Results: The results showed that the current ISO rear-facing envelopes can provide reasonable classifications for CRSs and vehicles, but the forward-facing envelopes do not represent products currently in the U.S. market. In particular, all of the selected vehicles could accommodate the largest forward-facing CRS envelope at the second-row seat location behind the driver seat. In contrast, half of the selected CRSs could not fit within any of the forward-facing ISO CRS envelopes, mainly due to protrusion at the rear-top corner of the envelope. The results also indicate that the rear seat compartment in U.S. vehicles often cannot accommodate a large portion of convertible CRSs in the rear-facing position. The increased demand for vehicle fuel economy and the recommendation to keep children rear-facing longer may lead to smaller cars and larger CRSs, which may increase the potential for fit problems.Conclusions: The virtual classifications indicated that contact between the forward-facing CRSs and the head restraints in the rear seats as well as that between the rear-facing CRSs and the back of the front seats is a main concern regarding the compatibility between the vehicles and the CRSs. Therefore, modification of the current ISO forward-facing CRS envelopes will likely to be necessary to ensure that they are useful for the U.S. market.

Comparative Performance of Forward-Facing Child Restraint Systems on the C/FMVSS 213 Bench and Vehicle Seats

Objective: The objective of this study was to evaluate the fidelity of the C/FMVSS 213 test bench, by comparing the dynamic performance of forward-facing child restraint systems (FFCRS) mounted on the C/FMVSS 213 sled bench versus mounted on a selection of production vehicle seats.Methods: The C/FMVSS 213 bench or one of 3 second-row original equipment manufacturer vehicle seats was mounted to the deck of acceleration crash sled. An FFCRS with a restrained anthropomorphic test device (ATD) was secured by 3-point belt (3-PT) or LATCH lower anchor (LLA) on the C/FMVSS 213 bench or vehicle seat, with or without a tether. The sled was then exposed to a 48 km/h acceleration pulse. Three unique make and model vehicle seats and FFCRS were tested. Fifty-three sled tests were performed.Results: When FFCRS were secured with LLA and no tether, little difference between the vehicle seats and 213 bench was observed. Similarly, when FFCRS were affixed with 3-PT and no tether, few kinematic variable differences achieved statistical significance; chest resultant acceleration was, on average, 9.1 g (SD = 6.6, P =.006) higher on the vehicle seats compared to the bench, as was CRS seatback excursion (difference [Δ] of 39.8 mm, SD = 32.7, P =.011) and ATD knee excursion (Δ = 36.4 mm, SD = 12.0, P < .001). However, when the tether was added to either the 3-PT or LLA attachment methods, the difference between the bench and vehicle seats was more pronounced. ATD kinematic measures such as head resultant acceleration (Δ = 14.6 g, SD = 7.2, P <.001) and pelvis resultant acceleration (Δ = 8.6 g, SD = 6.0, P =.005) were higher on the vehicle seats compared to the bench, as were the injury metrics for head and chest injury: ΔHIC15 = 162.2 (SD = 87.4, P =.001) and ΔChest 3 ms clip = 5.5 g (SD = 6.2, P =.040). Of note, CRS (Δ = 62.8 mm, SD = 32.7, P =.000) and ATD head (Δ = 66.3 mm, SD = 30.9, P =.000) and knee (Δ = 46.9 mm, SD = 25.8, P =.001) forward excursion were all higher on the vehicle seats compared to the bench in 3-PT with tether condition.Conclusions: Without the tether attached, we observed few kinematic and kinetic differences between the vehicle seat and the C/FMVSS 213 bench, suggesting that the bench is an adequate surrogate for the vehicle seat in this condition. With the tether attached, we found significant differences between the C/FMVSS 213 bench and vehicle seats, suggesting that the fidelity of the bench could be improved in the tethered mode. When differences were statistically significant, excursion and injury metrics were generally greater on the vehicle seats than on the C/FMVSS 213 bench.

The Impact of New Legislation on Child Restraint System (CRS) Misuse and Inappropriate Use in Australia

Objective: The current study aimed to investigate the incidence of child restraint system (CRS) misuse and/or inappropriate use of CRS through an Australian CRS inspection program conducted by CRS fitting specialists between October 2004 and October 2011 and to determine whether CRS misuse and/or inappropriate use of CRS changed following new Australian legislation regarding CRS and motor vehicle restraint use for children aged 7 years and under. Methods: Participants were recruited through an advertisement for free CRS inspections displayed at childcare centers, kindergartens, community centers, hospitals, and child expos. At each inspection, a CRS fitting specialist inspected each child in their CRS while in their vehicle and reported to the owner of the CRS on the installation of the child restraint(s) and/or system(s) and any fitting faults and/or concerns with the fitting and/or use of the child restraint(s) and or system(s). Results: Results are based on the inspection of 2674 CRS. Of all of the CRS inspected, the majority (79%) were reported as having at least one instance of misuse and/or inappropriate use. The most common forms of CRS misuse and/or inappropriate use observed were harness strap errors (twisted, poorly adjusted, and/or incorrectly positioned, 41%), seat belt errors (incorrectly routed, twisted, and/or incorrectly adjusted, 32%), and a missing or incorrect fitting of the gated buckle/locking clip (24%). Significant differences were found across the proportion of CRS misuse and/or inappropriate use across restraint types (infant restraint/forward-facing CRS/convertible [birth to 18 kg] CRS/convertible [8–26 kg] CRS/boosters [booster seat/cushion/booster with harness combination]), χ2(4) = 147.852, P < .001. CRS misuse and/or inappropriate use were most prevalent among convertible CRS (birth to 18 kg; 87%), forward-facing CRS (85%), and convertible CRS (8–26 kg; 81%), compared to infant restraints (73%) and booster seats (booster seats/cushions/boosters with H-harness combination; 65%). There was no significant difference in the proportion of CRS with misuse and/or inappropriate use across the pre- and post-legislation period (80% vs. 77%), χ2(1) = 1.545, P > .5. Conclusions: Based on the findings of the current study, it was concluded that, despite the introduction of new, definitive CRS legislation, CRS misuse and/or inappropriate use remains widespread in Australia. The findings highlight the need for CRS education and legislation that include information on correct CRS use, as well as information on appropriate CRS use, in order to provide specialized protection for child vehicle occupants in the event of a motor vehicle crash.

Observed use of tethers in forward-facing child restraint systems

BackgroundUse of top tethers with forward-facing child restraints is a simple way for parents to keep their children safer when travelling in passenger vehicles, but tether use remains low.ObjectivesTo obtain...

Child Restraint System Misuse and/or Inappropriate Use in Australia

Objective: Motor vehicle crashes are one of the leading causes of child death and acquired disability. Child restraint systems (CRS) for vehicles are designed to provide specialized protection for child occupants in the event of a crash. However, the effectiveness of a CRS is critically dependent on: correct installation of the CRS in the vehicle, the correct harnessing of the child in the CRS, and use of an appropriate CRS. The current study aimed to investigate the incidence misuse and/or inappropriate use of CRS through a CRS inspection program in the Australian states of New South Wales (NSW), Victoria (VIC), Queensland (QLD), South Australia (SA), Western Australia (WA), and Tasmania (TAS). Methods: Participants were recruited through an advertisement for free CRS inspections displayed at childcare centers, kindergartens, community centers, hospitals, and child expos. At each inspection, the CRS fitting specialist inspected and reported to the owner of the CRS on the installation of the child restraint(s) and/or system(s) and any fitting faults and/or concerns with the fitting and/or use if the child restraint(s) and or system(s). Results: The following results are based on the inspection of 1386 vehicles, in which there were 1995 restraints. Of all the restraints inspected, the majority (79%) were reported as having at least one instance of misuse. The most common forms of misuse included harness strap errors such as the straps being adjusted, faulty, twisted, and/or incorrectly positioned (38%); seat belt errors such as the seatbelt being incorrectly routed, twisted, and/or incorrectly adjusted (32%); missing or incorrect fitting of gated buckle/locking clip (23%); the need for a missing sash guide (8%); tether errors such as the tether being incorrectly routed and/or adjusted (7%); inappropriate use of a CRS for the size of the child (6%); anchor errors such as the anchor was fitted incorrectly or not the correct type (5%); and the H Harness1 being used incorrectly (5%). In addition, there were significant differences across restraint types in terms of the proportion of restraints with CRS misuse or fitment errors, χ2 (2) = 51.42, p < 0.001. The rate of misuse was highest for the forward-facing CRS (88%), compared to infant seats (67%) and booster seats or cushions (63%). 1 An H harness is an additional device that is designed for use with or without booster seats for children weighing up to 32 kg. The harness is attached to the vehicle at the same point as a CRS top tether, with the lap belt of the vehicle threaded through the harness. Discussion: The results show that CRS misuse and fitment errors are widespread in Australia. Based on the findings of this study, it is recommended that educational and awareness materials and programs that provide information on the safety benefits associated with correct CRS use (as well as the injury risk associated with CRS misuse) be developed for both parents and children.