Occupant responses in conventional and ABTS seats in high-speed rear sled tests

Objective: This study compared biomechanical responses of a normally seated Hybrid III dummy on conventional and all belts to seat (ABTS) seats in 40.2 km/h (25 mph) rear sled tests. It determined the difference in performance with modern (≥2000 MY) seats compared to older (<2000 MY) seats and ABTS seats.

Methods: The seats were fixed in a sled buck subjected to a 40.2 km/h (25 mph) rear sled test. The pulse was a 15 g double-peak acceleration with 150 ms duration. The 50th percentile Hybrid III was lap–shoulder belted in the FMVSS 208 design position. The testing included 11 <2000 MY, 8 ≥2000 MY, and 7 ABTS seats. The dummy was fully instrumented, including head accelerations, upper and lower neck 6-axis load cells, chest acceleration, thoracic and lumbar spine load cells, and pelvis accelerations. The peak responses were normalized by injury assessment reference values (IARVs) to assess injury risks. Statistical analysis was conducted using Student's t test. High-speed video documented occupant kinematics.

Results: Biomechanical responses were lower with modern (≥2000 MY) seats than older (<2000 MY) designs. The lower neck extension moment was 32.5 ± 9.7% of IARV in modern seats compared to 62.8 ± 31.6% in older seats (P =.01). Overall, there was a 34% reduction in the comparable biomechanical responses with modern seats. Biomechanical responses were lower with modern seats than ABTS seats. The lower neck extension moment was 41.4 ± 7.8% with all MY ABTS seats compared to 32.5 ± 9.7% in modern seats (P =.07). Overall, the ABTS seats had 13% higher biomechanical responses than the modern seats.

Conclusions: Modern (≥2000 MY) design seats have lower biomechanical responses in 40.2 km/h rear sled tests than older (<2000 MY) designs and ABTS designs. The improved performance is consistent with an increase in seat strength combined with improved occupant kinematics through pocketing of the occupant into the seatback, higher and more forward head restraint, and other design changes. The methods and data presented here provide a basis for standardized testing of seats. However, a complete understanding of seat safety requires consideration of out-of-position (OOP) occupants in high-speed impacts and consideration of the much more common, low-speed rear impacts.     

Thoracic and lumbar spine responses in high-speed rear sled tests

Objective: This study analyzed thoracic and lumbar spine responses with in-position and out-of-position (OOP) seated dummies in 40.2 km/h (25 mph) rear sled tests with conventional and all-belts-to-seat (ABTS) seats. Occupant kinematics and spinal responses were determined with modern (≥2000 MY), older (<2000 MY), and ABTS seats.

Methods: The seats were fixed in a sled buck subjected to a 40.2 km/h (25 mph) rear sled test. The pulse was a 15 g double-peak acceleration with 150 ms duration. The 50th percentile Hybrid III was lap–shoulder belted in the FMVSS 208 design position or OOP, including leaning forward and leaning inboard and forward. There were 26 in-position tests with 11 <2000 MY, 8 ≥2000 MY, and 7 ABTS and 14 OOP tests with 6 conventional and 8 ABTS seats. The dummy was fully instrumented. This study addressed the thoracic and lumbar spine responses. Injury assessment reference values are not approved for the thoracic and lumbar spine. Conservative thresholds exist. The peak responses were normalized by a threshold to compare responses. High-speed video documented occupant kinematics.

Results: The extension moments were higher in the thoracic than lumbar spine in the in-position tests. For <2000 MY seats, the thoracic extension moment was 76.8 ± 14.6% of threshold and the lumbar extension moment was 50.5 ± 17.9%. For the ≥2000 MY seats, the thoracic extension moment was 54.2 ± 26.6% of threshold and the lumbar extension moment was 49.8 ± 27.7%. ABTS seats provided similar thoracic and lumbar responses. Modern seat designs lowered thoracic and lumbar responses. For example, the 1996 Taurus had ?1,696 N anterior lumbar shear force and ?205.2 Nm extension moment. There was ?1,184 N lumbar compression force and 1,512 N tension. In contrast, the 2015 F-150 had ?500 N shear force and ?49.7 Nm extension moment. There was ?839 N lumbar compression force and 535 N tension. On average, the 2015 F-150 had 40% lower lumbar spine responses than the 1996 Taurus. The OOP tests had similar peak lumbar responses; however, they occurred later due to the forward lean of the dummy.

Conclusions: The design and performance of seats have significantly changed over the past 20 years. Modern seats use a perimeter frame allowing the occupant to pocket into the seatback. Higher and more forward head restraints allow a stronger frame because the head, neck, and torso are more uniformly supported with the seat more upright in severe rear impacts. The overall effect has been a reduction in thoracic and lumbar loads and risks for injury.     

Influence of the feedback links of connected and automated vehicle on rear-end collision risks with vehicle-to-vehicle communication

Objective: Connected and automated vehicles (CAV) can monitor multiple vehicles ahead via vehicle-to-vehicle (V2V) communication. Although feedback information from more vehicles ahead may be more helpful for anticipations, it also makes control more complex and increases the probability of data packet loss. Then it needs an appropriate number of CAV feedback links, and the maximum number may be not suitable. Therefore, this article focuses on the influence of CAV feedback links on rear-end collision risks.

Methods: To deal with this, stability analysis of a CAV car-following model was conducted to obtain the designs of CAV feedback gains for maintaining stable CAV flow. Simulation experiments were performed to describe a traffic accident on freeway, using car-following models of manually driven vehicles (MDVs) and CAV under different CAV penetration rates. Four scenarios are considered in simulation experiments; that is, the CAV monitors 1, 2, 3, and 4 preceding vehicles, respectively. Based on the simulation experiments, surrogate safety indicators, time-exposed time-to-collision (TET), and time-integrated time-to-collision (TIT) are used to evaluate risks of rear-end collisions.

Results: Results indicated that CAV helped to decrease the collision risks, especially the more serious collision risks with smaller threshold values of time-to-collision (TTC). In addition, the reductions in collision risks are more obvious when CAV feedback changes from one link to 2 links. In addition, reducing amplitudes are not significant if the CAV feedback is extended from 2 links to 3 or 4 links.

Conclusions: Two links of CAV feedback are appropriate when control complexity is a priority, whereas 3 links is the better choice when reductions in collisions are a priority. The findings of this study provide helpful reference for CAV control and design before larger-scale implementation in real vehicles.     

Severity of motorcycle crashes in Dar es Salaam,Tanzania

Objective: Motorcycles are a common mode of transportation in low- and middle-income countries. Tanzania, in particular, has experienced an increased use of motorcycles in the last decade. In Dar es Salaam, motorcycles provide door-to-door travel and often operate where more conventional services are uneconomical or physically impossible to maneuver. Although motorcycles play a crucial role in improving mobility in the city, they have several safety issues. This study focuses on identifying factors influencing the severity of motorcycle crashes.

Method: A multinomial logit analysis was conducted to identify factors influencing the severity of motorcycle crashes in Dar es Salaam, Tanzania. The severity categories were fatal, severe injury, minor injury, and property damage only (PDO). The analysis was based on a total of 784 motorcycle crashes that occurred from 2013 to 2016.

Results: The following factors were found to increase the probability of a fatality: Speeding, driving under the influence, head-on impact, presence of horizontal curves, reckless riding, off-peak hours, violations, and riding without a helmet. The results indicate that crashes occurring on weekdays, during peak hours, at intersections, involving a rear-end impact, in daylight, on street roads, and under clear weather conditions decrease the probability of a fatality. However, minor injury and PDO crashes were found to be associated with crashes occurring during peak hours, at intersections, and on street roads, as well as failure to yield right-of-way.

Conclusions: Several countermeasures are recommended based on the study findings. The recommended countermeasures focus on the holistic safety improvement strategies constituting the three Es of highway safety, namely, engineering, education, and enforcement.     

Alignment of the Lumbar Vertebrae in a Driving Posture

The purpose of this study was to define the anatomical arrangement of the lumbar spine in the mid-body sagittal plane of a human volunteer while in three postures: a driving posture; full flexion; and full extension. Radiographic images of the lumbar spine were made of a 33-year old 50th percentile male subject seated in a comfortable driving posture. Additional radiographs were made of the lumbar spine while the subject was postured in full voluntary flexion, and full voluntary extension. Anterior and posterior mid-sagittal vertebral endplate positions were plotted on an x-y coordinate system for each posture. Anterior and posterior disk thicknesses, and the positions of the centers of each vertebra were numerically determined using information from the plots. Disk thicknesses were then graphed and comparisons made for each posture. The arrangements of the centers of vertebrae were graphed and compared for the three different postures. The arrangement of the lumbar vertebrae tended toward that of full voluntary flexion while the subject was in a normal driving posture. Anterior disk thickness was a sensitive indicator of posture, while posterior disk thickness was not. While in a driving posture, the lower back approximated a straight-line that was nearly parallel to the seat back axis. The observations support those of an earlier study. Since soft tissue spinal elements can only be damaged by applying tensile forces in excess of their tolerance, the anterior elements of the lumbar spine would not be directly threatened in low velocity frontal collisions, since anterior elements would be in relative compression. Tension injury to the anterior structures as a result of a rear-end collision would first require reversing the preimpact conditions imposed by the normal driving posture. Tension injury to the posterior spinal elements resulting from low velocity rear-end collisions would be unlikely since axial compression loading would also diminish tension stress in posterior soft tissue structures. Any compression injury to posterior elements resulting from rear-end collisions would first require reversing the pre-impact conditions imposed by the normal driving posture.     

Low-velocity motor vehicle collision characteristics associated with claimed low back pain

Objective: Up to 50% of individuals involved in low-velocity motor vehicle collisions report low back pain (LBP). A major limitation in such cases is the lack of knowledge of injury mechanisms linking the collision characteristics to the pain and pathology associated with LBP reporting. Thus, the objective of this investigation was to characterize the physical circumstances of low-velocity motor vehicle collisions that resulted in claims of LBP.

Methods: Eighty-three forensically assessed cases were analyzed to identify specific collision and claimant characteristics.

Results: Seventy-seven percent of reviewed cases involved a claim of LBP. Of these LBP claim cases, 70% of cases involved a rear-end collision configuration, and 40% of all cases were low-velocity collisions, with severities ranging between 10 and 12?km/h. The most common pre-existing medical condition was prior LBP or evidence of disc degeneration.

Conclusions: The results of this investigation provide knowledge of collision characteristics that can be employed in future studies on the mechanisms of low back injury in low-speed motor vehicle collisions.     

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

Objective: 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.     

Effects of whole spine alignment patterns on neck responses in rear end impact

Objective: The aim of this study was to investigate the whole spine alignment in automotive seated postures for both genders and the effects of the spinal alignment patterns on cervical vertebral motion in rear impact using a human finite element (FE) model.

Methods: Image data for 8 female and 7 male subjects in a seated posture acquired by an upright open magnetic resonance imaging (MRI) system were utilized. Spinal alignment was determined from the centers of the vertebrae and average spinal alignment patterns for both genders were estimated by multidimensional scaling (MDS). An occupant FE model of female average size (162 cm, 62 kg; the AF 50 size model) was developed by scaling THUMS AF 05. The average spinal alignment pattern for females was implemented in the model, and model validation was made with respect to female volunteer sled test data from rear end impacts. Thereafter, the average spinal alignment pattern for males and representative spinal alignments for all subjects were implemented in the validated female model, and additional FE simulations of the sled test were conducted to investigate effects of spinal alignment patterns on cervical vertebral motion.

Results: The estimated average spinal alignment pattern was slight kyphotic, or almost straight cervical and less-kyphotic thoracic spine for the females and lordotic cervical and more pronounced kyphotic thoracic spine for the males. The AF 50 size model with the female average spinal alignment exhibited spine straightening from upper thoracic vertebra level and showed larger intervertebral angular displacements in the cervical spine than the one with the male average spinal alignment.

Conclusions: The cervical spine alignment is continuous with the thoracic spine, and a trend of the relationship between cervical spine and thoracic spinal alignment was shown in this study. Simulation results suggested that variations in thoracic spinal alignment had a potential impact on cervical spine motion as well as cervical spinal alignment in rear end impact condition.     

Secondary collisions and injury severity: A joint analysis using structural equation models

Objective: This study aims to investigate the contributing factors to secondary collisions and the effects of secondary collisions on injury severity levels. Manhattan, which is the most densely populated urban area of New York City, is used as a case study. In Manhattan, about 7.5% of crash events become involved with secondary collisions and as high as 9.3% of those secondary collisions lead to incapacitating and fatal injuries.

Methods: Structural equation models (SEMs) are proposed to jointly model the presence of secondary collisions and injury severity levels and adjust for the endogeneity effects. The structural relationship among secondary collisions, injury severity, and contributing factors such as speeding, alcohol, fatigue, brake defects, limited view, and rain are fully explored using SEMs. In addition, to assess the temporal effects, we use time as a moderator in the proposed SEM framework.

Results: Due to its better performance compared with other models, the SEM with no constraint is used to investigate the contributing factors to secondary collisions. Thirteen explanatory variables are found to contribute to the presence of secondary collisions, including alcohol, drugs, inattention, inexperience, sleep, control disregarded, speeding, fatigue, defective brakes, pedestrian involved, defective pavement, limited view, and rain. Regarding the temporal effects, results indicate that it is more likely to sustain secondary collisions and severe injuries at night.

Conclusions: This study fully investigates the contributing factors to secondary collisions and estimates the safety effects of secondary collisions after adjusting for the endogeneity effects and shows the advantage of using SEMs in exploring the structural relationship between risk factors and safety indicators. Understanding the causes and impacts of secondary collisions can help transportation agencies and automobile manufacturers develop effective injury prevention countermeasures.     

Cross-correlation between the controlled collision environment and real-world motor vehicle collisions: Evaluating the protection of the thoracic side airbag

Objective: Thoracic side airbags (tSABs) were integrated into the vehicle fleet to attenuate and distribute forces on the occupant's chest and abdomen, dissipate the impact energy, and move the occupant away from the intruding structure, all of which reduce the risk of injury. This research piece investigates and evaluates the safety performance of the airbag unit by cross-correlating data from a controlled collision environment with field data.

Method: We focus exclusively on vehicle–vehicle lateral impacts from the NHTSA's Vehicle Crash Test Database and NASS-CDS database, which are replicated in the controlled environment by the (crabbed) barrier impact. Similar collisions with and without seat-embedded tSABs are matched to each other and the injury risks are compared.

Results: Results indicated that dummy-based thoracic injury metrics were significantly lower with tSAB exposure (P <.001). Yet, when the controlled collision environment data were cross-correlated with NASS-CDS collisions, deployment of the tSAB indicated no association with thoracic injury (tho. MAIS 2+ unadjusted relative risk [RR] = 1.14; 90% confidence interval [CI], 0.80–1.62; tho. MAIS 3+ unadjusted RR = 1.12; 90% CI, 0.76–1.65).

Conclusion: The data from the controlled collision environment indicated an unequivocal benefit provided by the thoracic side airbag for the crash dummy; however, the real-world collisions demonstrate that no benefit is provided to the occupant. This has resulted from a noncorrelation between the crash test/dummy-based design taking the abstracting process too far to represent the real-world collision scenario.     

Safe speed limits for a safe system: The relationship between speed limit and fatal crash rate for different crash types

Objective: The objective of this article is to provide empirical evidence for safe speed limits that will meet the objectives of the Safe System by examining the relationship between speed limit and injury severity for different crash types, using police-reported crash data.

Method: Police-reported crashes from 2 Australian jurisdictions were used to calculate a fatal crash rate by speed limit and crash type. Example safe speed limits were defined using threshold risk levels.

Results: A positive exponential relationship between speed limit and fatality rate was found. For an example fatality rate threshold of 1 in 100 crashes it was found that safe speed limits are 40 km/h for pedestrian crashes; 50 km/h for head-on crashes; 60 km/h for hit fixed object crashes; 80 km/h for right angle, right turn, and left road/rollover crashes; and 110 km/h or more for rear-end crashes.

Conclusions: The positive exponential relationship between speed limit and fatal crash rate is consistent with prior research into speed and crash risk. The results indicate that speed zones of 100 km/h or more only meet the objectives of the Safe System, with regard to fatal crashes, where all crash types except rear-end crashes are exceedingly rare, such as on a high standard restricted access highway with a safe roadside design.     

Implications of head and neck restraint test repeatability for specification improvement

Objective: Since 2005, National Association for Stock Car Auto Racing, Incorporated (NASCAR) drivers have been required to use a head and neck restraint system (HNR) that complies with SFI Foundation, Inc. (SFI) 38.1. The primary purpose of the HNR is to control and limit injurious neck loads and head kinematics during frontal and frontal oblique impacts. The SFI 38.1 performance specification was implemented to establish a uniform test procedure and minimum standard for the evaluation of HNRs using dynamic sled testing. The purpose of this study was to evaluate the repeatability of the current SFI 38.1 test setup and explore the effects of a polyester seat belt restraint system.

Method: Eight sled tests were conducted using the SFI 38.1 sled test protocol with additional test setup constraints. Four 0° frontal tests and 4 30° right frontal (RF) oblique tests were conducted. The first 3 tests of each principal direction of force (PDOF) used nylon SFI 16.1 seat belt restraint assemblies. The fourth test of each PDOF used polyester SFI 16.6 seat belt restraint assemblies. A secondary data set (Lab B Data) was also supplied by the HNR manufacturer for further comparisons. The International Organization for Standardization (ISO) 18571 objective comparison method was used to quantify the repeatability of the anthropomorphic test device (ATD) resultant head, chest, and pelvis acceleration and upper neck axial force and flexion extension bending moment time histories across multiple tests.

Results: Two data sets generated using the SFI 38.1 test protocol exhibited large variations in mean ISO scores of ATD channels. The 8 tests conducted with additional setup constraints had significantly lower mean ISO score coefficients of variation (CVs). The Lab B tests conducted within the current specification but without the additional test setup constraints had larger mean ISO score standard deviation and CV for all comparisons. Specifically, tests with the additional setup constraints had average CVs of 3.3 and 2.9% for the 0° and 30° RF orientations, respectively. Lab B tests had average CVs of 22.9 and 24.5%, respectively. Polyester seat belt comparisons had CVs of 5.3 and 6.2% for the 0° and 30° RF orientations, respectively.

Conclusion: With the addition of common test setup constraints, which do not violate the specification, the SFI 38.1 test protocol produced a repeatable test process for determining performance capabilities of HNRs within a single sled lab. A limited study using polyester webbing seat belt assemblies versus the nylon material called for in SFI 38.1 indicates that the material likely has less effects on ATD upper neck axial force and flexion extension bending moment time histories than the test setup freedom currently available within the specification. The additional test setup constraints are discussed and were shown to improve ATD response repeatability for a given HNR.     

Variability in vehicle and dummy responses in rear-end collisions

OBJECTIVE: The objective of this study was to quantify the occupant response variability due to differences in vehicle and seat design in low-speed rear-end collisions. METHODS: Occupant response variability was quantified using a BioRID dummy exposed to rear-end collisions in 20 different vehicles. Vehicles were rolled rearward into a rigid barrier at 8 km/h and the dynamic responses of the vehicle and dummy were measured with the head restraint adjusted to the up most position. In vehicles not damaged by this collision, additional tests were conducted with the head restraint down and at different impact speeds. RESULTS: Despite a coefficient of variation (COV) of less than 2% for the impact speed of the initial 8 km/h tests, the vehicle response parameters (speed change, acceleration, restitution, bumper force) had COVs of 7 to 23% and the dummy response parameters (head and T1 kinematics, neck loads, NIC, N(ij) and N(km)) had COVs of 14 to 52%. In five vehicles tested multiple times, a head restraint in the down position significantly increased the peak magnitude of many dummy kinematic and kinetic response parameters. Peak head kinematics and neck kinetics generally varied linearly with head restraint back set and height, although the neck reaction moment reversed and increased considerably if the dummy's head wrapped onto the top of the head restraint. CONCLUSIONS: The results of this study support the proposition that the vehicle, seat, and head restraint are a safety system and that the design of vehicle bumpers and seats/head restraint should be considered together to maximize the potential reduction in whiplash injuries.     

Adaptation of a Canadian culpability scoring tool to Alberta police traffic collision report data

Objective: The objective of this study was to adapt a previously validated Canadian Culpability Scoring Tool (CCST) to Alberta police report data.

Methods: Police traffic collision reports from motor vehicle (MV) collisions in Calgary and Edmonton (Alberta, Canada) from 2010 to 2014 were used. Adaptation of the CCST was completed with input from personnel within Alberta Transportation, contributing to face and content validity. Two research assistants, given only the information necessary for scoring, evaluated 175 randomly selected MV–MV collisions. Interrater agreement was estimated using kappa (k) and reported with 95% confidence intervals (CIs). Discussion of disagreements between the research assistants and consultation from Alberta Transportation informed the algorithm used in the Alberta Motor Vehicle Collision Culpability Tool (AMVCCT). The AMVCCT was automated and applied to all motorists involved in collisions. Binary logistic regression was used to examine characteristics of the culpable and nonculpable drivers and their effects were reported using odds ratios (ORs) with 95% CIs.

Results: Interrater agreement for the random sample was excellent (k = 0.95; 95% CI, 0.92–0.99). Of those drivers hospitalized, 1,130 (37.54%) were rated not culpable and 1,880 (62.46%) were rated culpable. The odds of being culpable were higher for males than for females (OR = 1.43; 95% CI, 1.23–1.66). The odds of being culpable were higher in those impaired by alcohol than those considered “apparently normal” (OR = 61.10; 95% CI, 22.66–164.75). The odds of being deemed culpable, when compared with drivers >54 years old, were higher for those <25 years old (OR = 1.72; 95% CI, 1.35–2.20) and lower for those in the 40- to 54-year-old age group (OR = 0.78; 95% CI, 0.63–0.96). Driving between 12 a.m. and 6 a.m. resulted in higher odds of being culpable compare with all other 6-h time blocks. Direction and statistical significance remained consistent when applying the tool to all MV collisions. Sensitivity analysis including the removal of single vehicle collisions did not affect the direction or statistical significance of the main results.

Conclusions: The AMVCCT identified a culpable group that exhibited characteristics expected in drivers who are at fault in collisions. The age groups 25–39 and 40–54 demonstrated different results than the CCST. However, this is the only difference that exists in the findings of the AMVCCT compared to the CCST and could exist due to differences between the driving populations in Alberta and British Columbia. It is possible to adapt the CCST to provinces outside British Columbia and, in doing so, we can identify risk factors for collision contribution and not-at-fault drivers who represent the driving population.     

Effects of LATCH versus Available Seatbelt Installation of Rear Facing Child Restraint Systems on Head Injury Criteria for 6 Month Old Infants in Rear End Collisions

Objective: The Lower Anchor and Tethers for CHildren (LATCH) system was introduced in vehicles made after September 1, 2002 and intended to make installation of rear and forward-facing child safety seats easier. Due to the lack of rear impact testing of RFCRS required per the Federal Motor Vehicle Safety Standards (FMVSS), the purpose of this study was to explore the effects, if any, of installation method of RFCRS on the performance of commonly purchased makes and models of RFCRS. Specifically, we hypothesize that in a 48 km/h (29.8 MPH) rear-end collision, installation of RFCRS using the LATCH system will result in higher Head Injury Criteria (HIC) values when compared to using the available lap/shoulder seatbelt (Emergency Locking Retractor - ELR or Automatic Locking Retractor - ALR).

Methods: The test matrix included 36 rear impact sled tests conducted using 3 installation methods on 3 models of RFCRS: the Graco SnugRide® with and without the base, the Britax Chaperone with base-mounted anti-rebound bar, and the Evenflo Tribute®, a model of convertible rearward/forward facing restraint system used in the rearward facing mode. The seats were installed using the LATCH system, ELR lap/shoulder belts, or ALR lap/shoulder belts in seating positions 4 and 6 on a vehicle buck mounted to the sled test base. The infant seat and 6 month old CRABI anthropometric test device (ATD) installation methods were in accordance with standards set forth in the National Highway Traffic Safety Administration's (NHTSA) FMVSS No. 213, Child Restraint Systems. All tests were conducted on pneumatic controlled acceleration sled (HYGE, Inc., PA, USA) at 48 km/h.

Results: Installation of infant seat type RFCRS using the LATCH system resulted in higher HIC₁₅ values when compared to using the available lap/shoulder seatbelt (ELR or ALR). The mean HIC₁₅ values were most severe when infant seat type RFCRS were installed using LATCH (Graco SnugRide® HIC₁₅ = 394 and Britax Chaperone HIC₁₅ = 133) compared to using either ELR lap/shoulder belts (Graco SnugRide® HIC₁₅ = 218 and Britax Chaperone HIC₁₅ = 65) or ALR lap/shoulder belts (Graco SnugRide® HIC₁₅ = 194 and Britax Chaperone HIC₁₅ = 78). The installation method did not result in a statistically significant difference in HIC for the convertible type RFCRS (Evenflo Tribute®). In many of the tests, the ATD's head struck the seatback in which the RFCRS was installed. These head strikes resulted in the higher HIC₁₅ scores recorded throughout the testing.

Conclusions: The results of this study suggest that LATCH does not offer equal protection to lap/shoulder belts from head injuries in rear impacts when used with infant seat type RFCRS.     

Cervical and thoracic spine injury in pediatric motor vehicle crash passengers

Objective: Motor vehicle occupants aged 8 to 12 years are in transition, in terms of both restraint use (booster seat or vehicle belt) and anatomical development. Rear-seated occupants in this age group are more likely to be inappropriately restrained than other age groups, increasing their vulnerability to spinal injury. The skeletal anatomy of an 8- to 12-year-old child is also in developmental transition, resulting in spinal injury patterns that are unique to this age group. The objective of this study is to identify the upper spine injuries commonly experienced in the 8- to 12-year-old age group so that anthropomorphic test devices (ATDs) representing this size of occupant can be optimized to predict the risk of these injuries.

Methods: Motor vehicle crash cases from the National Trauma Data Bank (NTDB) were analyzed to characterize the location and nature of cervical and thoracic spine injuries in 8- to 12-year-old crash occupants compared to younger (age 0–7) and older age groups (age 13–19, 20–39).

Results: Spinal injuries in this trauma center data set tended to occur at more inferior vertebral levels with older age, with patients in the 8- to 12-year-old group diagnosed with thoracic injury more frequently than cervical injury, in contrast to younger occupants, for whom the proportion of cases with cervical injury outnumbered the proportion of cases with thoracic injury. With the cervical spine, a higher proportion of 8- to 12-year-olds had upper spine injury than adults, but a substantially lower proportion of 8- to 12-year-olds had upper spine injury than younger children. In terms of injury type, the 8- to 12-year-old group’s injury patterns were more similar to those of teens and adults, with a higher relative proportion of fracture than younger children, who were particularly vulnerable to dislocation and soft tissue injuries. However, unlike for adults and teens, catastrophic atlanto-occipital dislocations were still more common than any other type of dislocation for 8- to 12-year-olds and vertebral body fractures were particularly frequent in this age group.

Conclusions: Spinal injury location in the cervical and thoracic spine moved downward with age in this trauma center data set. This shift in injury pattern supports the need for measurement of thoracic and lower cervical spine loading in ATDs representing the 8- to 12-year-old age group.     

Evaluation of the effectiveness of toe board energy-absorbing material for foot,ankle, and lower leg injury reduction

Objective: Since 2000, numerous improvements have been made to the National Association for Stock Car Auto Racing, Incorporated (NASCAR®) driver restraint system, resulting in improved crash protection for motorsports drivers. Advancements have included seats, head and neck restraints (HNRs), seat belt restraint systems, driver helmets, and others. These enhancements have increased protection for drivers from severe crash loading. Extending protection to the driver's extremities remains challenging. Though the drivers’ legs are well contained for lateral and vertical crashes, they remain largely unrestrained in frontal and frontal oblique crashes.

Method: Sled testing was conducted for the evaluation of an energy-absorbing (EA) toe board material to be used as a countermeasure for leg and foot injuries. Testing included baseline rigid toe boards, tests with EA material–covered toe boards, and pretest positioning of the 50th percentile male frontal Hybrid III anthropomorphic test device (ATD) lower extremities. ATD leg and foot instrumentation included foot acceleration and tibia forces and moments.

Results: The sled test data were evaluated using established injury criteria for tibial plateau fractures, leg shaft fractures, and calcaneus, talus, ankle, and midfoot fractures.

Conclusion: A polyurethane EA foam was found to be effective in limiting axial tibia force and foot accelerations when subjected to frontal impacts using the NASCAR motorsport restraint system.     

Analysis of naturalistic driving videos of fleet services drivers to estimate driver error and potentially distracting behaviors as risk factors for rear-end versus angle crashes

Objective: The objective of this study was to estimate the prevalence and odds of fleet driver errors and potentially distracting behaviors just prior to rear-end versus angle crashes.

Methods: Analysis of naturalistic driving videos among fleet services drivers for errors and potentially distracting behaviors occurring in the 6 s before crash impact. Categorical variables were examined using the Pearson's chi-square test, and continuous variables, such as eyes-off-road time, were compared using the Student's t-test. Multivariable logistic regression was used to estimate the odds of a driver error or potentially distracting behavior being present in the seconds before rear-end versus angle crashes.

Results: Of the 229 crashes analyzed, 101 (44%) were rear-end and 128 (56%) were angle crashes. Driver age, gender, and presence of passengers did not differ significantly by crash type. Over 95% of rear-end crashes involved inadequate surveillance compared to only 52% of angle crashes (P < .0001). Almost 65% of rear-end crashes involved a potentially distracting driver behavior, whereas less than 40% of angle crashes involved these behaviors (P < .01). On average, drivers spent 4.4 s with their eyes off the road while operating or manipulating their cell phone. Drivers in rear-end crashes were at 3.06 (95% confidence interval [CI], 1.73–5.44) times adjusted higher odds of being potentially distracted than those in angle crashes.

Conclusions: Fleet driver driving errors and potentially distracting behaviors are frequent. This analysis provides data to inform safe driving interventions for fleet services drivers. Further research is needed in effective interventions to reduce the likelihood of drivers' distracting behaviors and errors that may potentially reducing crashes.