Comparison of child and ATD belt fit and posture on belt-positioning boosters during self-selected, holding device, and nominal conditions.

OBJECTIVE: Pediatric anthropomorphic test devices (ATDs) are important tools for the assessment of child occupant protection and should represent realistic child belt fit and posture on belt-positioning boosters. Previous comparisons have been made to children in either self-selected or nominal postural conditions. This study compares belt fit and postural measurements between pediatric ATDs and a single cohort of children assuming different postures on boosters: self-selected, holding a portable electronic device, and nominal. METHODS: A cohort of children (n = 25) were evaluated in a stationary vehicle on five boosters and in three postural conditions: nominal, self-selected, and a representative holding electronic device position. The Hybrid III 6- and 10-year-old and Q-Series 6- and 10-year-old ATDs were evaluated in the same five boosters and in two postural conditions: nominal and a representative holding electronic device position. A 3D coordinate measurement device was used to quantify belt fit (shoulder belt score, lap belt score, maximum gap size, and gap length) and anatomic landmark positions (head, suprasternale, ASIS, and patella). Landmark positions and belt fit were compared between ATDs and children for each booster and postural condition, and Pearson correlations (r) were assessed across boosters. RESULTS: ATDs generally represented Nominal child postures across boosters. In the Device condition, ATDs were seldom able to be positioned to represent both the torso and head position of children, due to limited ATD spinal flexibility. When the torso position was matched, the ATD head was more rear by 63 mm. Correlations between Nominal child and ATD belt fit and belt gap metrics were generally weak and not significant, with the exception of lap belt score (all ATDs p < 0.07, r = 0.8549-0.9857). DISCUSSION: ATDs were generally able to represent realistic child postures and lap belt fit in Nominal and short duration Self-selected postures in a laboratory setting. However, these results display the potential difficulty of utilizing ATDs to represent more naturalistic child postures, especially the more forward head positions and flexed spinal posture associated with utilizing a portable electronic device.

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.

Effects of restraint parameters using PIPER 6y in reclined seating during frontal impact.

OBJECTIVE: This study explores possible challenges for child occupants in reclined seating positions, applying current protection systems. Using PIPER 6 y in frontal impacts, the aim was to investigate the effect of restraint parameters in reclined seating positions, in addition to an upright position, varying booster design, shoulder belt outlet, and pretensioner activation. METHOD: Eighteen full frontal impacts were simulated using the PIPER 6 y human body model restrained on a booster in a front passenger seat. The type of booster, pretensioner activation and shoulder belt outlet were varied with the vehicle seat in 'upright position' (25°) and 'reclined position' (40°). Three booster principles were used: booster seat (BoosterA), booster cushion (BoosterB) and representing properties of a vehicle built-in booster cushion (BoosterC). The two shoulder belt outlets include 'nominal D-ring' and 'rearward D-ring´. RESULTS: Overall, activation of the pretensioner reduced the overall body displacement as well as the head and neck response in both seating positions. Submarining occurred only in the case of BoosterB in 'reclined position' without pretensioner. Some differences were observed for the lap belt interaction with pelvis in the non-submarining simulations. Greater pelvis displacement was observed in 'reclined position' as compared to 'upright position'. In both seating positions, greatest pelvis displacement was observed for BoosterB, due to relatively more forward initial lap belt position. While both provided favorable initial lap belt to pelvis contact, BoosterC offered more efficient lap belt restraint than BoosterA, since the lap belt remained lower on the pelvis and the vertical movement of the pelvis was more limited compared to BoosterA. When in 'reclined position', the 'rearward D-ring' position enabled earlier coupling of the torso due to initial shoulder belt to shoulder contact, resulting in lower head and neck responses as well as shorter head displacement compared to 'nominal D-ring'. CONCLUSIONS: Submarining can be addressed in reclined seating positions using current booster design in combination with a seatbelt pretensioner. Lap belt routing was influenced by booster design and reclined seating, affecting the overall kinematics and responses of the PIPER 6 y. This study highlights the importance of including the whole context of child occupant protection when investigating reclined seating, such as the interaction and compatibility of booster, vehicle seat and seatbelt.

Child restraint headrest and belt routing design features and their association with child passenger behavior and restraint misuse.

OBJECTIVES: Ergonomic design of child restraint systems (CRS) may facilitate optimal travel behavior and crash protection of child passengers during motor vehicle trips. However there have been few studies examining the relationship between CRS design and child passenger travel behavior. The aim of this study was to examine whether associations between CRS design features and child passenger behavior exist during real-world, everyday vehicle trips. METHODS: Video from a naturalistic driving study (NDS) was analyzed in this study. Families drove an instrumented study vehicle for approximately two weeks with at least one child aged between one and eight years traveling in their own forward-facing (FF) CRS or belt positioning booster (BPB). Video for one child passenger was randomly selected from each trip for analysis. Video was coded for five-second epochs at nine time points (5%, 17%, 25%, 30%, 50%, 53%, 75%, 89% and 95% of trip length). Two types of child passenger travel behaviors were identified by manual review of the video and audio recordings: (i) optimal/suboptimal head position and (ii) correct/incorrect use of the internal harness/shoulder belt. Video screenshots were used to characterize CRS design features. Random effects logistic regression models were used to examine the associations between specific CRS design features and the travel behaviors of interest, whilst accounting for clustering of data by child and trip. RESULTS: Suboptimal head position was associated with the absence of a height adjustable headrest and a narrow headrest wing width in FFCRS. Incorrect harness use in a FFCRS was associated with the absence of an adjustable headrest, in addition to headrest features such as wing width and depth. In BPBs, a reduction in suboptimal head position was associated with the absence of a sash belt guide, however no restraint design features were associated with incorrect shoulder belt use. CONCLUSIONS: Some CRS design features may influence undesirable child passenger travel behavior. These early findings support enhanced and user-centric CRS design as a likely important mechanism to improve child passenger safety.

Understanding users' characteristics in the selection of vehicle seating configurations and positions in fully automated vehicles.

OBJECTIVE: To understand which users' characteristics influence their preferences in the selection of vehicle seating configurations and positions across different traveling scenarios involving a fully automated vehicle (FAV). METHODS: Participants (n = 730) completed an online survey in which they were asked to imagine traveling in a FAV across three hypothetical scenarios. Participants were asked to select between five different seating configurations and four positions for each scenario and about their anthropometry and their driving/riding experience. Multinomial regression analyses were conducted to identify the factors that influenced users' preferences. RESULTS: FAV Configuration #3 (traditional light vehicle seating configuration) was the preferred seating configuration for 74% of the participants, followed by FAV #2 (in which the two seating rows face each other, 13%) in Scenario 1 (riding by oneself). Similar numbers were observed in Scenario 3 (riding with an unknown person). In Scenario 2 (riding with their partner), participants preferred FAV #2 (12.5%) and FAV #5 (in which the front seat passengers point toward a common point in the front, conventional rear seat configuration, 17.5%). Having close family was significant to choose the traditional vehicle configuration over other vehicle configurations, but only when the participants were driving by themselves. Having previously experienced motion sickness was significant to prefer a forward seating configuration when the trip was shared with partners. Belonging to a particular height or weight group was significantly associated with the preferred seat within the preferred FAV configuration (the driver's position in FAV #3; a rear-facing seat in FAV #2), although there was not a clear trend between increasing weight and/or height and preferring one seating position over the others. CONCLUSIONS: Previous work had shown differences in participants' preferences for seating configurations and positions depending on age, sex and country. While increasing the sample size, the current study analyses other factors that were associated with choosing one vehicle configuration and seating position over others. As these factors are directly related to the likelihood of sustaining injuries in the event of a crash, the current study provides important insights regarding the potential risk factors for FAV occupants.

Evaluation of users' experience and posture in a rotated swivel seating configuration.

OBJECTIVE: This study aims to evaluate a car passenger's experience and actions in a rotated seat in terms of interaction with an adjacent passenger. METHODS: A static user study was conducted, using a stationary test vehicle with two front row seats facing rearwards. The seats were mounted on a swivel plate which allowed inboard rotation. Thirty-two participants in 16 test pairs were grouped based on stature; short or tall. The participants within each pair knew each other. Three seating configurations were evaluated; 0° and 10° and 20° inboard rotated position of both seats. The participants were seated in each seating configuration for 10 min; 5 min they engaged in a conversation with each other and 5 min they were watching media on an Ipad mounted in front of them. Subjective data from each participant on their experiences and preferences were collected through questionnaires, and objective data on sitting postures and eye gaze were collected through video recording. RESULTS: Ninety-two percent of the short participants preferred to sit in the 20° rotated seating configuration when watching media and 75% preferred the 20° seating configuration when engaged in conversation. Compared to short participants, the tall participants showed a relative larger spread in seating configuration preference; 15% and 30% of them preferred the reference position for media and conversation, respectively. Leg interference was common for tall participants when 20° inboard rotated. They perceived it uncomfortable and used various strategies to avoid contact, including crossing legs or feet. Time spent with mutual eye contact did not vary by seating configuration. CONCLUSIONS: This static user study shows that rotated seats could be a desired seating configuration in future autonomous vehicles for individuals who know each other. It reveals the reasons behind the preferences and the extent of desired seat rotation, showing differences between tall and short individuals. By understanding how occupant position and posture can be influenced by offering various seating configurations, the occupant can choose a comfortable position that is also safe. The leg and feet positions are raised as the body region with most variations and for which an increased understanding of influence in a crash is encouraged.

Booster cushion design effects on child occupant kinematics and loading assessed using the PIPER 6-year-old HBM and the Q10 ATD in frontal impacts.

OBJECTIVE: Our objective was to study the effect on child occupant kinematics and loading by differences in booster cushion designs and attachment in a frontal impact. METHODS: Three different booster cushion designs were exposed to a frontal impact in vehicle rear seat interiors. The boosters were selected based on their difference in shape, stiffness, and guiding loop design. Tests were run varying the shoulder belt routing above or under the guiding loop, in addition to with or without attachment of the booster cushion to the vehicle ISOFIX anchorages. Eighteen simulations with the finite element PIPER 6-year-old human body model (HBM) were run investigating all combinations of parameters, in addition to 3 sled tests with a Q10 anthropomorphic test dummy (ATD). RESULTS: Across 2 different child sizes, using an HBM and an ATD, respectively, consistent sensitivity to the booster design differences were seen. Boosters providing similar initial static belt fit can result in different occupant responses during a crash, due to the design of the boosters and their dynamic performance. Compression of the booster cushion resulted in a delayed pelvis restraint, influencing the upper body kinematics. The guiding loop design as well as the belt routing above or under the guide also influenced the upper body kinematics and shoulder belt interaction. CONCLUSIONS: Early pelvis coupling to initiate torso pitch, and thereby an upper torso motion controlled by the shoulder belt, is the preferred occupant protection for booster-seated children. A stable mid-shoulder belt position centered over the chest initially is a prerequisite. Additionally, it was seen that the design of the guiding loops helps provide favorable interaction with the torso during the crash. The option to allow the shoulder belt to be placed above and under the guiding loops will accommodate a larger span of child sizes and adapt to more vehicle seat belt geometries. This study provides evidence that the design of the booster cushion plays an important role in creating an early pelvis coupling, as well as supporting favorable torso-shoulder belt interaction.

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.

A comparison of seat belt fit and comfort experience between older adults and younger front seat passengers in cars.

Objective: The purpose was to study how occupant age affects seat belt fit and comfort by comparing older adults and younger occupants in the front seat of a passenger vehicle.Methods: An exploratory user study was performed for the front seat of a stationary large passenger vehicle in a laboratory environment, including 11 older (aged 72-81) and 11 younger (aged 25-30) participants. Each participant first entered the vehicle and buckled up in a predefined seat position. Next, they adjusted the seat to their preferred seat position and buckled up again. Anthropometric data were collected on height, weight, and waist and hip circumferences. Photographs and measurements were taken of seat/seat belt positions and posture, and structured interviews were conducted regarding comfort perceptions of the 2 tested scenarios, including previous experience and awareness of seat belt usage and discomfort experienced as passengers in cars.Results: Nonoptimal belt fit included shoulder belt on the shoulder edge or close to the neck or lap belt over the abdomen. Five of 11 older adults had nonoptimal belt fit in the predefined position, and in the preferred position 7 older adults had nonoptimal belt fit. Only one showed safety awareness and recognized the nonoptimal belt fit in the preferred position. In the younger group, 4 of 11 had nonoptimal belt fit in the predefined position and 4 in the preferred position. Two acknowledged the nonoptimal belt fit. Older adult participants with a more pronounced kyphotic posture had the upper part of the shoulder belt positioned closer to the suprasternal notch compared to younger participants. Older adults were also more likely to have the lower part of the shoulder belt higher up on the abdomen compared to younger participants. Participants with higher body mass indexes (BMIs) were more likely to have the shoulder belt higher up on the abdomen, independent of age and gender. When the shoulder belt was positioned higher up on the abdomen the upper portion of the shoulder belt was routed closer to the throat. Older adults preferred to sit higher up to achieve a better field of vision compared to younger adults.Conclusions: The change in body posture due to aging influences belt fit. Older adults seemed less aware of safety related to belt fit. Increased BMI influenced shoulder belt fit, independent of age. These findings are important when designing restraint systems to ensure safety for all occupants.

Seating configuration and position preferences in fully automated vehicles.

Objective: This study aimed to understand seating configuration and position preferences in a fully automated vehicle (FAV) across 7 hypothetical traveling scenarios.Methods: Participants completed an online survey in which they were asked to imagine traveling in an FAV across 7 hypothetical traveling scenarios and asked to select 1 of 5 seating configurations and 1 of 4 seating positions for themselves and for any additional occupants. Furthermore, participants were asked to indicate any activities that they and any additional occupants would engage in and whether they would be willing to wear a different seat belt in an FAV while seated in a non-forward-facing mode or while reclined.Results: Five hundred and fifty-two participants (male = 50.5%; mean = 36.6 years, SD = 14.0 years) completed the online survey. Most participants resided in Australia (40.9%), Spain (16.5%), Sweden (15.6%), or Lebanon (19.4%). Most participants drove on a daily basis (60.0%), had driven between 5,000 and 15,000 km in the previous year (33.2%), and reported that they always or almost always wear a seat belt while traveling in a motor vehicle (98.2%). Across all scenarios, participants were most likely to prefer a conventional seating configuration (i.e., all seats facing forward; between 40.0 and 76.3%). In terms of seating position preferences, participants preferred seating position A (i.e., the conventional driver's seat; between 54.6 and 68.3%), regardless of with whom they were traveling. The most common activity while traveling alone was reading (25.0%). However, when traveling with other occupants, talking was the most common activity (41.0-63.0%), even with someone they did not know (31.0%). Most participants predicted that they would always or almost always wear a seat belt when traveling in an FAV (95.9%). Most participants also reported that they would be very willing or willing to wear a different seat belt configuration in an FAV while seated in a non-forward-facing mode or while reclined (73.8 and 80.7%, respectively).Conclusions: This study has provided valuable insight regarding seating configuration and position preferences in an FAV, as well as predicted activities and restraint use. Future research will use this information to simulate likely injury outcomes of these preferences in the event of a motor vehicle crash and provide a basis for the design of occupant protection systems for FAVs.

Kinematics and shoulder belt engagement of children on belt-positioning boosters during evasive steering maneuvers.

OBJECTIVE: To increase the protection of child passengers in crashes preceded by evasive steering, understanding of how children interact with the seat belt in such situations is essential. This study aims to quantify child kinematics and describe child-to-restraint interaction during evasive steering maneuvers. METHODS: Eighteen child volunteers (aged 5-10) were seated on the rear seat of a passenger vehicle. A professional driver made repeatable sharp turns at 50 km/h. Children were restrained by the seat belt on a booster cushion (BC) and on an integrated booster cushion (IBC). Kinematics of the nasion and upper sternum were analyzed with video tracking software and shoulder belt (SB) engagement and position were evaluated. RESULTS: Children moved laterally inboard, and SB-to-body interaction was influenced by booster and stature. Shorter children displayed initial SB positions closer to the neck with less instances of gap between the SB and the lower torso, resulting in more curved belt paths on the IBC. On the BC, shorter children had less of the SB in contact with the torso and straight belt paths were observed throughout steering. Taller children generally had the SB initially mid-shoulder with less instances of gap, resulting in curved belt paths at initial and maximum displacements on both boosters. Children loaded the shoulder belt by axially rotating their torso into the SB more often on the IBC compared to BC. The SB generally stayed on the shoulder, with 89% of slip-off instances occurring for shorter children on the BC. Shorter children on the BC had the largest average inboard nasion displacement (120 mm). Taller children on the BC had the lowest average inboard displacement of the nasion (100 mm). All children initially displaced on average 90 mm inboard with their upper sternum. CONCLUSIONS: Initial SB position on the shoulder and torso differed with booster and stature, which influenced how children engaged with the seat belt during steering. Children with less SB initially in contact with the torso moved laterally behind the belt, resulting in straighter SB paths and outboard motion of the SB on the shoulder (often ending far out or slipped off). When more of the SB was initially in contact with the torso, children tended to engage the SB more, moving with the belt and causing the SB path to become more curved, resulting in less inboard head displacement and less outboard motion of the SB on the shoulder. Enhanced understanding of how evasive steering affects the kinematic response of children provides valuable data for protection of children in real-world situations.

Frontal and oblique crash tests of HIII 6-year-old child ATD using real-world, observed child passenger postures.

OBJECTIVE: The aim of this study was to evaluate the consequences of frontal and oblique crashes when positioning a Hybrid III (HIII) 6-year-old child anthropometric test device (ATD) using observed child passenger postures from a naturalistic driving study (NDS). METHODS: Five positions for booster-seated children aged 4-7 years were selected, including one reference position according to the FMVSS 213 ATD seating protocol and 4 based on real-world observed child passenger postures from an NDS including 2 user positions with forward tilting torso and 2 that combined both forward and lateral inboard tilting of the torso. Seventeen sled tests were conducted in a mid-sized vehicle body at 64 km/h (European New Car Assessment Programme [Euro NCAP] Offset Deformable Barrier [ODB] pulse), in full frontal and oblique (15°) crash directions. The rear-seated HIII 6-year-old child ATD was restrained on a high-back booster seat. In 10 tests, the booster seat was also attached with a top tether. In the oblique tests, the ATD was positioned on the far side. Three camera views and ATD responses (head, neck, and chest) were analyzed. RESULTS: The shoulder belt slipped off the shoulder in all ATD positions in the oblique test configuration. In full frontal tests, the shoulder belt stayed on the shoulder in 3 out of 9 tests. Head acceleration and neck tension were decreased in the forward leaning positions; however, the total head excursion increased up to 210 mm compared to te reference position, due to belt slip-off and initial forward leaning position. CONCLUSIONS: These results suggest that real-world child passenger postures may contribute to shoulder belt slip-off and increased head excursion, thus increasing the risk of head injury. Restraint system development needs to include a wider range of sitting postures that children may choose, in addition to the specified postures of ATDs in seating test protocols, to ensure robust performance across diverse use cases. In addition, these tests revealed that the child ATD is limited in its ability to mimic real-world child passenger postures. There is a need to develop child human body models that may offer greater flexibility for these types of crash evaluations.

Modelling how drivers respond to a bicyclist crossing their path at an intersection: How do test track and driving simulator compare?

Bicyclist fatalities are a great concern in the European Union. Most of them are due to crashes between motorized vehicles and bicyclists at unsignalised intersections. Different countermeasures are currently being developed and implemented in order to save lives. One type of countermeasure, active safety systems, requires a deep understanding of driver behaviour to be effective without being annoying. The current study provides new knowledge about driver behaviour which can inform assessment programmes for active safety systems such as Euro NCAP. This study investigated how drivers responded to bicyclists crossing their path at an intersection. The influences of car speed and cyclist speed on the driver response process were assessed for three different crossing configurations. The same experimental protocol was tested in a fixed-base driving simulator and on a test track. A virtual model of the test track was used in the driving simulator to keep the protocol as consistent as possible across testing environments. Results show that neither car speed nor bicycle speed directly influenced the response process. The crossing configuration did not directly influence the braking response process either, but it did influence the strategy chosen by the drivers to approach the intersection. The point in time when the bicycle became visible (which depended on the car speed, the bicycle speed, and the crossing configuration) and the crossing configuration alone had the largest effects on the driver response process. Dissimilarities between test-track and driving-simulator studies were found; however, there were also interesting similarities, especially in relation to the driver braking behaviour. Drivers followed the same strategy to initiate braking, independent of the test environment. On the other hand, the test environment affected participants' strategies for releasing the gas pedal and regulating deceleration. Finally, a mathematical model, based on both experiments, is proposed to characterize driver braking behaviour in response to bicyclists crossing at intersections. This model has direct implications on what variables an in-vehicle safety system should consider and how tests in evaluation programs should be designed.

Seat belt pre-pretensioner effect on child-sized dummies during run-off-road events.

OBJECTIVE: Run-off-road events occur frequently and can result in severe consequences. Several potential injury-causing mechanisms can be observed in the diverse types of run-off-road events. Real-world data show that different types of environments, such as rough terrain, ditch types, and whether multiple events occur, may be important contributing factors to occupant injury. Though countermeasures addressing front seat occupants have been presented, studies on rear seat occupant retention in situations such as run-off-road events are lacking. The aim of this study was to investigate the seat belt pre-pretensioner effect on rear-seated child-sized anthropomorphic test devices (ATDs) during 2 different types of run-off-road events. METHODS: The study was carried out using 2 test setups: a rig test with a vehicle rear seat mounted on a multi-axial robot simulating a road departure event into a side ditch and an in-vehicle test setup with a Volvo XC60 entering a side ditch with a grass slope, driving inside the ditch, and returning back to the road from the ditch. Potential subsequent rollovers or impacts were not included in the test setups. Three different ATDs were used. The Q6 and Q10 were seated on an integrated booster cushion and the Hybrid III (HIII) 5th percentile female was positioned directly on the seat. The seat belt retractor was equipped with a pre-pretensioner (electrical reversible retractor) with 3 force level settings. In addition, reference tests with the pre-pretensioner inactivated were run. Kinematics and the shoulder belt position were analyzed. RESULTS: In rig tests, the left-seated ATD was exposed to rapid inboard lateral loads relative to the vehicle. The displacement for each ATD was reduced when the pre-pretensioner was activated compared to tests when it was inactivated. Maximum inboard displacement occurred earlier in the event for all ATDs when the pre-pretensioner was activated. Shoulder belt slip-off occurred for the Q6 and Q10 in tests where the pre-pretensioner was inactivated. During in-vehicle tests, the left-seated ATD was exposed to an inboard movement when entering the road again after driving in the ditch. The maximum inboard head displacement was reduced in tests where the pre-pretensioner was activated compared to tests in which it was inactivated. CONCLUSIONS: During both test setups, the activation of the pre-pretensioner resulted in reduced lateral excursion of the Q6, Q10, and HIII 5th percentile female due to the shoulder belt remaining on the shoulder and supporting the side of the lower torso. The results provide new insights into the potential benefits of using a pre-pretensioner to reduce kinematic responses during complex run-off-road events through supporting the seat belt to remain on the shoulder. This study addresses potential countermeasures to improve real-world protection of rear-seated children, and it provides a broader perspective including the influence of precrash kinematics.

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

OBJECTIVE: 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.

Misuse of booster cushions among children and adults in Shanghai-an observational and attitude study during buckling up.

OBJECTIVE: Traffic crashes are one of the leading causes of fatalities among Chinese children. Booster cushion usage in China is low, and there are no studies showing how a population with limited experience handles booster cushions during buckling up. The purpose of this study was to evaluate the handling of and explore the attitudes toward booster cushions among children, parents, and grandparents in Shanghai. METHODS: An observational study including a convenience sample of 254 children aged 4-12 years was conducted in 2 passenger cars at a shopping center in Shanghai. Parents, grandparents, or the children themselves buckled up the child on 2 types of booster cushions, a 2-stage integrated booster cushion (IBC) and an aftermarket booster cushion (BC). The test participants were observed during buckling up, first without and then with instructions. The test leaders conducted structured interviews. RESULTS: Ninety-eight percent of the uninstructed participants failed to buckle up without identified misuse on the aftermarket booster cushion and 31% of those uninstructed on the integrated booster cushion. The majority of misuse was severe, including placing the belt behind the arm and the lap belt routing above the guiding loops. Instruction reduced misuse to 58% (BC) and 12% (IBC), respectively, and, in particular, severe misuse. Some misuse was related to limited knowledge of how to buckle up on the booster cushion, and some misuse was intentional in order to reduce discomfort. The participants, both children and adults, reported that they preferred the IBC due to good comfort and convenience. Safety was reported as the main reason for adults using booster cushions in general, whereas children reported comfort as the most important motivation. CONCLUSIONS: Education is needed to ensure frequent and correct use of booster cushions in China and to raise safety awareness among children and adults. Furthermore, it is important that the booster cushions offer intuitively correct usage to a population with limited experience of booster cushions. This is the first study published on the handling of and attitude toward booster cushions after child restraints laws were introduced in Shanghai 2014.

Responses of the Q6/Q6s ATD Positioned in Booster Seats in the Far-Side Seat Location of Side Impact Passenger Car and Sled Tests.

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.

Children's and Adults' Comfort Experience of Extra Seat Belts When Riding in the Rear Seat of a Passenger Car.

OBJECTIVE: The objective of this study was to explore passengers' comfort experience of extra seat belts during on-road driving in the rear seat of a passenger car and to investigate how the use of extra belts affects children's and adults' attitudes to the product. METHODS: Two different seat belt systems were tested, criss-cross (CC) and backpack (BP), consisting of the standard 3-point belt together with an additional 2-point belt. In total, 32 participants (15 children aged 6-10, 6 youths aged 11-15, and 11 adults aged 20-79, who differed considerably in size, shape, and proportions) traveled for one hour with each system, including city traffic and highway driving. Four video cameras monitored the test subject during the drive. Subjective data regarding emotions and perceived discomfort were collected in questionnaires every 20 min. A semistructured interview was held afterwards. RESULTS: All participant groups accepted the new products and especially the increased feeling of safety (P <.01); 56% preferred CC and 44% preferred BP but the difference was not significant. In total, 81% wanted to have extra seat belts in their family car. CC was appreciated for its symmetry, comfort, and the perceived feeling of safety. Some participants found CC unpleasant because the belts tended to slip close to the neck, described as a strangling feeling. BP was simpler to use and did not cause annoyance to the neck in the way CC did. Instead, it felt asymmetric and to some extent less safe than CC. Body size and shape affected seat belt fit to a great extent, which in turn affected the experience of comfort, both initially and over time. Perceived safety benefit and experienced comfort were the most determinant factors for the attitude toward the extra seat belts. The extra seat belts were perceived as being better than the participants had expected before the test, and they became more used to them over time. CONCLUSION: This exploratory study provided valuable knowledge from a user perspective for further development of new seat belt systems in cars. In addition to an increased feeling of safety, seat belt fit and comfort are supplementary influencing factors when it comes to gaining acceptance of new seat belt systems.

Pretensioner loading to rear-seat occupants during static and dynamic testing.

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. 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. Abdominal loading to the Q10 in the static pretensioner deployments indicated a low risk of abdominal injury in all tested positions. CONCLUSION: 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.

Long-term medical consequences for child occupants 0 to 12 years injured in car crashes.

OBJECTIVE: There is limited knowledge of the long-term medical consequences for children injured in car crashes. Thus, in the event of injury, the aim of the study was to specify patterns and risks of injuries resulting in permanent medical impairment of children (0-12 years) for different body regions and injury severity levels, according to Abbreviated Injury Scale (AIS). The aim was also to compare the impairment outcome with adults. METHODS: Data were obtained from the Folksam insurance company, including reported car crashes from 1998 to 2010 with at least one injured child 0-12 years of age. In all, 2619 injured children with 3704 reported medical diagnoses were identified. All injuries were classified according to the AIS 2005 revision. If the child had not recovered within 1 year postinjury an assessment of permanent medical impairment (PMI) was made by one or several medical specialists. RESULTS: In all, 55 children sustained 59 injuries resulting in PMI of which 75 percent were at AIS 1 or AIS 2. The head and cervical spine were the body regions sustaining the most injuries resulting in PMI. Sixty-eight percent of all injuries resulting in PMI were AIS 1 injuries to the cervical spine, with the majority occurring in frontal or rear impacts. Given an injury to the cervical spine, the risk of injuries resulting in PMI was 3 percent, and older children (≥6 years) had a significantly higher risk (3% versus 1%) than younger children. The head was the second most commonly injured body region with injuries resulting in PMI (12/59), which were predominantly AIS 2+. In addition, mild traumatic brain injuries at AIS 1 were found to lead to PMI. Whereas for children the injuries leading to PMI were primarily limited to the head and cervical spine, adults sustained injuries that led to PMI from a more diverse distribution of body regions. CONCLUSION: The pattern of injuries resulting in permanent medical impairment is different for children and adults; therefore, safety priorities for children need to be based on child data. The majority of those injuries leading to PMI were at lower AIS levels. Furthermore, AIS 1 cervical spine and AIS 1+ head injuries should be given priority concerning mitigation of long-term consequences for children.