Comparison of frontal crash compatibility metrics between battery-electric and internal-combustion-engine passenger vehicles.

OBJECTIVE: The objective of this study was to determine if there are any emerging issues related to battery-electric vehicles' (BEVs') geometry, force distribution, and extra weight that may make them more aggressive partners in front-to-front crashes through comparisons of stiffness metrics derived from crash tests. METHODS: We examined load cell wall data from the National Highway Traffic Safety Administration's (NHTSA's) New Car Assessment Program full-width frontal crash test at 56 km/h. Fourteen BEVs, ranging in class from small cars to large SUVs, were compared with 92 internal-combustion-engine (ICE) vehicles, ranging in class from small cars to midsize pickups. We selected vehicles based on the test results available in the NHTSA Vehicle Crash Test Database, and there were no tests of battery-electric (BE) pickups. Data included load-cell-wall force-time histories and longitudinal vehicle acceleration from the body structure. We constructed force-displacement diagrams and calculated static, dynamic, energy-equivalent, and initial front-end-stiffness metrics from load cell wall forces, vehicle acceleration, and static front-end crush measurements for each vehicle. Linear regression models were applied to the metrics for comparison between powertrains. RESULTS: BE cars and BE SUVs weighed more than their ICE counterparts, on average 369 kg and 286 kg more, respectively. Initial (200 mm and 400 mm), energy-equivalent and dynamic front-end-stiffness metrics, average height of force, and individual maximum forces, when compared with vehicle shadow, were not statistically different between powertrains. Static stiffness (p = 0.04) and initial stiffness (300 mm; p = 0.05) decreased for BEVs with greater shadow and increased with greater shadow for ICE vehicles. When controlling for vehicle shadow, dynamic crush was greater (p = 0.01), the percentage of center force was lower (p < 0.001), and maximum peak force was higher (p = 0.01) for BEVs compared with ICE vehicles. For the Kia Niro BEV and ICE pair, the 329 kg heavier BEV had a 165 mm longer crush distance, which resulted in lower forces and stiffness metrics compared with the traditional ICE counterpart. CONCLUSION: Overall, this study indicates that current BEVs are not excessively aggressive in terms of stiffness metrics for frontal crash compatibility compared with ICE vehicles.

How can front crash prevention systems address more police-reported crashes in the United States?

Government and consumer-information organizations can motivate automakers to address additional crash types through front crash prevention (FCP) testing programs. This study examined the current state of crashes potentially relevant to current and future FCP systems to provide a roadmap for the next crash types that vehicle testing programs in the United States should evaluate. Crash records from 2016 to 2020 were extracted from the Crash Report Sampling System (CRSS) and the Fatality Analysis Reporting System (FARS). Crashes were restricted to ones involving no more than two vehicles where the striking or path-intruding vehicle was a passenger vehicle and a vehicle defect was not coded. Percentages of police-reported crashes, nonfatal-injury crashes, and fatal crashes were computed for different crash types and circumstances. Rear-end and pedestrian crashes evaluated in existing FCP testing programs accounted for 27% of all police-reported crashes, 19% of nonfatal-injury crashes, and 18% of fatal crashes. The remaining crash types relevant to FCP accounted for 25% of police-reported crashes, 31% of nonfatal-injury crashes, and 23% of fatal crashes. A turning passenger vehicle crossing the path of an oncoming vehicle accounted for the largest proportion of the remaining police-reported (8%) and nonfatal-injury crashes (13%). Head-on crashes accounted for the largest proportion of remaining fatal crashes (9%). Most FCP-relevant police-reported crashes occurred on roads with a posted speed limit between 30 and 50 mph. Medium/heavy trucks were the crash partner in a disproportionate number of fatal head-on and rear-end crashes and motorcycles in a disproportionate number of fatal rear-end and turning crossing-path crashes. Fatal bicyclist and pedestrian crashes were overrepresented at night. The findings from this study indicate that testing organizations should evaluate FCP performance at higher speeds; with non-passenger vehicles and vulnerable road users; during the night; and in more complex head-on and turning crash scenarios to reduce crashes of all severities. Some of these conditions are currently assessed by other testing organizations and can be readily adopted by U.S. programs or possibly addressed with new approaches like virtual testing.

Characteristics of automatic emergency braking responses in passenger vehicles evaluated in the IIHS front crash prevention program.

Researchers can estimate the potential safety benefits of front crash prevention (FCP) systems by simulating system performance in rear-end crash scenarios reported to police or captured during naturalistic driving. Data to support assumptions about FCP systems in production vehicles, particularly automatic emergency braking (AEB), are limited. This study used detailed information from the Insurance Institute for Highway Safety's (IIHS's) FCP evaluation to characterize interventions in vehicles that performed well (superior-rated vehicles) and those that did not perform as well (basic/advanced-rated vehicles) when approaching a stationary surrogate vehicle on a test track at 20 and 40 km/h, and estimated performance in similar conditions at higher speeds. Vehicle and video data from 3,231 IIHS FCP tests conducted at 20 and 40 km/h and 51 IIHS FCP research tests conducted at 50, 60, and 70 km/h with AEB responses were analyzed. Forward collision warning (FCW) and AEB time-to-collision (TTC), mean deceleration, maximum deceleration, and maximum jerk from the beginning of automatic braking to the end of braking or impact were computed for each test. Each dependent measure was modeled with test speed (20 km/h, 40 km/h), IIHS FCP test rating (superior, basic/advanced), and the interaction between test speed and rating. The models were used to estimate each dependent measure at 50, 60, and 70 km/h, and model predictions were compared with the observed performance of six vehicles in IIHS research test data. Vehicles with superior-rated systems warned and began braking earlier, had a greater average rate of deceleration, reached a higher peak deceleration, and had greater jerk than vehicles with basic/advanced-rated systems, on average. The interaction between test speed and vehicle rating was significant in each linear mixed-effects model, indicating that these differences changed with test speed. FCW and AEB in superior-rated vehicles occurred 0.05 and 0.10 s earlier, respectively, per 10-km/h increase in test speed compared with basic/advanced-rated vehicles. Mean deceleration and maximum deceleration for FCP systems in superior-rated vehicles increased 0.65 m/s2 and 0.60 m/s2 more, respectively, per 10-km/h increase in test speed than for systems in basic/advanced-rated vehicles. Maximum jerk increased 2.78 m/s3 per 10-km/h increase in test speed for basic/advanced-rated vehicles but decreased 0.25 m/s3 for systems in superior-rated vehicles. The root mean square error between the observed performance and estimated values at 50, 60, and 70 km/h indicated that the linear mixed-effects model had reasonable prediction accuracy for every measure except jerk at these out-of-sample data points. The findings from this study provide insight into the characteristics that make FCP effective for preventing crashes. Based on performance in the IIHS FCP test, vehicles with superior-rated FCP systems had earlier TTC thresholds and braked with greater deceleration that increased with speed compared with basic/advanced-rated systems. The linear mixed-effects models that were developed can guide assumptions about AEB response characteristics for superior-rated FCP systems in future simulation studies.

Investigation of factors influencing submarining mitigation with child booster seats.

OBJECTIVE: Automobile booster seats are intended to improve belt fit for children that are too large for a harness-style child restraint, but not yet big enough to fit properly in an adult seat belt. Our objective was to prospectively study the relationship between booster seat design and interaction with the seat belt (specifically, submarining risk) for a child occupant using computer simulation of automobile crash events. METHODS: Frontal-impact simulations were performed with a 6-year-old child human body model. Simplified models of booster seats were developed using an automated process designed to capture key characteristics of booster geometry, stiffness, belt guide construction, and attachment to the vehicle seat. The child model was positioned in a range of postures from upright to slouched. Our main interest was submarining, where the child's pelvis slips under the lap belt and the belt loads into the abdomen (defined based on the motion of the lower lap belt edge relative to the ASIS). RESULTS: Among the parameters studied, the factors that had the greatest effect on submarining risk were the booster's stiffness and the child's posture. Booster models of a low-stiffness construction (similar to an inflatable booster) nearly always resulted in submarining, regardless of the other design characteristics of the booster. A slouched posture also substantially increased the likelihood of submarining (even for high-stiffness boosters). CONCLUSIONS: These results suggest that booster seats of a stiffer construction, and booster seats that promote an upright posture may provide a protective benefit compared to softer boosters and boosters that are more likely to result in slouching of the child.

Injury risks and crashworthiness benefits for females and males: Which differences are physiological?

OBJECTIVE: Previous research has found elevated injury risk for females relative to males in passenger vehicle crashes but has not accounted for ways the crashes themselves differ between these populations. Vehicle curb weight, ride height, safety rating, airbag deployment, and crash configuration all influence injury outcome and often are not well-represented by delta-V alone. This study evaluated the effect of occupant sex on injury risk in front and side crashes while limiting or controlling for non-physiological crash differences. Additionally, the effects of crashworthiness improvements are compared for females and males. METHODS: NASS-CDS cases from 1998-2015 calendar years involving a belted driver in a front crash or a struck-side driver or right front passenger in a side crash were analyzed. Case vehicle model years were 1989-2016. Logistic regression was used to estimate the risk of MAIS ≥ 2 and MAIS ≥ 3 injury outcomes for females relative to males as well as the change in risk due to improved crashworthiness. Sex-based differences in occupant age, mass, and stature; crash test rating; delta-V; crash configuration; and vehicle-to-vehicle compatibility were considered either through case selection or the inclusion of additional regression covariates. RESULTS: Before controlling for crash and vehicle differences, female drivers in front crashes had higher estimated overall and body-region-specific risks of MAIS ≥ 2 and MAIS ≥ 3 injury, as consistent with previous findings. After accounting for such differences, all ratios of injury odds for females relative to males were reduced. Females remained at higher risk of MAIS ≥ 2 injury (OR, 2.23; 95% CI, 1.42-3.51), especially extremity injury, but had similar odds for MAIS ≥ 3 non-extremity injury (OR, 0.98; 95% CI, 0.56-1.7). While controlling for crash differences in side impacts, none of the estimated injury risk differences by sex were significant at the p ≤ 0.05 level. Estimated benefits of improved crashworthiness were similar or greater for females than for males for most injury outcomes. CONCLUSIONS: Female-specific crashworthiness improvements may be required to provide additional protection against AIS 2 extremity injury. Much of the remaining discrepancy in sex-based injury risk can be attributed differences between vehicles and crashes, not to physiological differences. Addressing these differences will require other types of countermeasures.

Fatal side impact crash scenarios for rear seat and seat belt-restrained occupants from vulnerable populations.

Objective: Previous studies have revealed vulnerability of school-age children and older adults in rear seats in motor vehicle crashes. Detailed information about crashes in which these fatalities occur could help improve vehicle and restraint design.Methods: Police accident reports were obtained for crashes from the Fatality Analysis Reporting System data set. Inclusion criteria were crashes in which there was at least one fatally injured restrained rear seat occupant between the ages of 6 and 12 or 55 and older in a passenger vehicle no older than 10 years at the time of the crash. Reports were reviewed for key crash data. Side impacts were selected for analysis.Results: Thirty-nine side impact crashes met the inclusion criteria, resulting in 46 fatalities of interest. Far-side or nondirect impact cases outnumbered near-side cases by 15-11 for juvenile occupants. Sixty-one percent of occupants were in vehicles with side airbags (SABs), all of which deployed for their position, although torso SABs were only present in 3 cases. Head injuries were present in all juvenile cases with injury data available and older occupants suffered equally from head and torso injuries. Impacts with pickup trucks and heavy trucks made up 31 and 22% of all cases, respectively. Three-quarters of cases were judged as survivable for the fatally injured occupant(s), and 5 of 7 cases deemed unsurvivable involved juvenile decedents. Further, of those deemed survivable, two-thirds had damage comparable in magnitude with the same vehicles in consumer information crash tests, evaluated by photo comparison.Conclusions: Older adults suffered thoracic injuries at a higher rate than older children-who suffered predominately head injuries-and most vehicles did not have torso SABs installed, which could have mitigated thoracic injuries. Side impacts in which younger occupants were killed were more severe than impacts that resulted in the death of an older occupant; however, vehicle damage and intrusion in many fatal impacts for both age cohorts appeared similar to that of consumer information testing. Large pickups and heavy vehicles were the striking vehicle in over half of all fatalities; vehicle designs and crash tests should continue to take this into consideration. This research highlights the need for continued work as the automotive safety community seeks to eliminate fatalities in motor vehicle crashes.

Passenger use of and attitudes toward rear seat belts.

OBJECTIVES: This study sought to identify attitudes toward belt use in the rear seat and to gain insight into the experiences of rear-seat passengers. METHOD: A telephone survey conducted between June and August 2016 targeted adult passengers who had recently ridden in the rear and who did not always wear their seat belt when doing so. Respondents were questioned regarding their reasons for not buckling up and possible conditions under which they would be more likely to buckle up during rear-seat travel. RESULTS: Of 1163 recent rear-seat passengers, 72% reported always using their seat belt in the rear. Full-time belt use was lower among passengers who primarily travel in the rear of hired vehicles compared with personal vehicles. The most common explanation for not buckling up was that the back seat is safer than the front. Four out of five agreed they do not buckle up because of type of trip; two-thirds forget or do not see the need; and two-thirds agreed with reasons related to design, comfort, or usability issues. Nearly 40% agreed that they sometimes do not buckle up in the rear because there is no law requiring it. CONCLUSION: Many reasons for not using belts in the rear are similar to reasons in the front, such as forgetfulness, inconvenience, or discomfort. One difference is that many rear-seat passengers perceive using the belt is unnecessary because the back seat is safer than the front. More than half of part-time belt users and nonusers reported interventions such as rear seat belt reminders, stronger belt-use laws, and more comfortable belts would make them more likely to use their seat belt in the rear seat. Practical applications: This study identifies barriers to rear seat belt use that point to the need for a multi-faceted approach to increase belt use.

Assessing tether anchor labeling and usability in pickup trucks.

OBJECTIVE: The objective of this study was to investigate vehicle factors associated with child restraint tether use and misuse in pickup trucks and evaluate 4 labeling interventions designed to educate consumers on proper tether use. METHODS: Volunteer testing was performed with 24 subjects and 4 different pickup trucks. Each subject performed 8 child restraint installations among the 4 pickups using 2 forward-facing restraints: a Britax Marathon G4.1 and an Evenflo Triumph. Vehicles were selected to represent 4 different implementations of tether anchors among pickups: plastic loop routers (Chevrolet Silverado), webbing routers (Ram), back wall anchors (Nissan Frontier), and webbing routers plus metal anchors (Toyota Tundra). Interventions included a diagram label, Quick Response (QR) Code linked to video instruction, coordinating text label, and contrasting text tag. RESULTS: Subjects used the child restraint tether in 93% of trials. However, tether use was completely correct in only 9% of trials. An installation was considered functional if the subject attached the tether to a tether anchor and had a tight installation (ignoring routing and head restraint position); 28% of subjects achieved a functional installation. The most common installation error was attaching the tether hook to the anchor/router directly behind the child restraint (near the top of the seatback) rather than placing the tether through the router and attaching it to the anchor in the adjacent seating position. The Nissan Frontier, with the anchor located on the back wall of the cab, had the highest rate of correct installations but also had the highest rate of attaching the tether to components other than the tether anchor (seat adjustor, child restraint storage hook, around head restraint). None of the labeling interventions had a significant effect on correct installation; not a single subject scanned the QR Code to access the video instruction. Subjects with the most successful installations spent extensive time reviewing the vehicle manuals. CONCLUSION: Current implementations of tether anchors among pickup trucks are not intuitive for child restraint installations, and alternate designs should be explored. Several different labeling interventions were ineffective at achieving correct tether use in pickup trucks.

Effects of an integrated collision warning system on teenage driver behavior.

INTRODUCTION: Crash warning systems have been shown to provide safety benefits, but no studies have examined how teenagers respond. This study sought to find out whether young, inexperienced drivers change behavior in response to warnings. METHODS: Forty 16-17 year-olds drove an instrumented vehicle equipped with a system that warned for lane departures and potential rear-end and lane change/merge crashes. Participants were randomly assigned to experimental or control groups, and their driving was monitored for 14weeks during 2011-12. For the experimental group, this included a treatment period, when crash alerts were received by drivers, and baseline and post-treatment periods, when warnings were recorded but not received. The control group never received warnings. Data were analyzed to determine whether warnings were associated with changes in driving behavior. RESULTS: A total of 15,039 trips were analyzed. Lane drifts accounted for 73% of warnings. Forward collision warning rates doubled for all drivers during the treatment period and continued at an increased rate post-treatment. This was likely a result of the fact that, as time went on, all drivers spent more time following vehicles at close distances. Receiving alerts was associated with effects on following and lane-changing behavior, including more time spent following at close distances (17%), fewer lateral drifts (37%) and fewer unsignaled lane changes (80%). Receiving warnings wasn't associated with an increased likelihood of engaging in secondary tasks. CONCLUSIONS: Warning systems may result in improved lane-keeping and turn-signal behaviors by novice drivers, but there is some indication they may result in more close-following behaviors. PRACTICAL APPLICATIONS: There is some evidence that lane departure warning may improve turn-signal use for young drivers. While there is no evidence of safety benefits from the other types of warnings, there is some evidence of an increase in close-following behavior but no increase in secondary tasks due to the presence of those capabilities.

Vehicle characteristics associated with LATCH use and correct use in real-world child restraint installations.

INTRODUCTION: The objective of this study was to determine if vehicle features associated with LATCH ease-of-use in laboratory studies with volunteers predict LATCH use and misuse in real-world child restraint installations. METHOD: Vehicle characteristics were extracted from prior surveys of more than 100 top-selling 2010-13 vehicles. Use and correct use of LATCH was determined from records of more than 14,000 child restraint installations in these vehicles that were inspected by child passenger safety technicians at Safe Kids car seat checkup events during 2010-12. Logistic regression was used to examine the association between vehicle features and use and correct use of lower anchors and top tethers, controlling for other relevant installation features. RESULTS: Lower anchors were more likely to be used and correctly used when the clearance angle around them was greater than 54°, the force required to attach them to the lower anchors was less than 178N, and their depth within the seat bight was less than 4cm. Restraints were more likely to be attached correctly when installed with the lower anchors than with the seat belt. After controlling for lower anchor use and other installation features, the likelihood of tether use and correct use in installations of forward-facing restraints was significantly higher when there was no hardware present that could potentially be confused with the tether anchor or when the tether anchor was located on the rear deck, which is typical in sedans. CONCLUSIONS: There is converging evidence from laboratory studies with volunteers and real-world child restraint installations that vehicle features are associated with correct LATCH use. PRACTICAL APPLICATIONS: Vehicle designs that improve the ease of installing child restraints with LATCH could improve LATCH use rates and reduce child restraint misuse.

Rear seat safety: Variation in protection by occupant, crash and vehicle characteristics.

OBJECTIVES: Current information on the safety of rear row occupants of all ages is needed to inform further advances in rear seat restraint system design and testing. The objectives of this study were to describe characteristics of occupants in the front and rear rows of model year 2000 and newer vehicles involved in crashes and determine the risk of serious injury for restrained crash-involved rear row occupants and the relative risk of fatal injury for restrained rear row vs. front passenger seat occupants by age group, impact direction, and vehicle model year. METHOD: Data from the National Automotive Sampling System Crashworthiness Data System (NASS-CDS) and Fatality Analysis Reporting System (FARS) were queried for all crashes during 2007-2012 involving model year 2000 and newer passenger vehicles. Data from NASS-CDS were used to describe characteristics of occupants in the front and rear rows and to determine the risk of serious injury (AIS 3+) for restrained rear row occupants by occupant age, vehicle model year, and impact direction. Using a combined data set containing data on fatalities from FARS and estimates of the total population of occupants in crashes from NASS-CDS, logistic regression modeling was used to compute the relative risk (RR) of death for restrained occupants in the rear vs. front passenger seat by occupant age, impact direction, and vehicle model year. RESULTS: Among all vehicle occupants in tow-away crashes during 2007-2012, 12.3% were in the rear row where the overall risk of serious injury was 1.3%. Among restrained rear row occupants, the risk of serious injury varied by occupant age, with older adults at the highest risk of serious injury (2.9%); by impact direction, with rollover crashes associated with the highest risk (1.5%); and by vehicle model year, with model year 2007 and newer vehicles having the lowest risk of serious injury (0.3%). Relative risk of death was lower for restrained children up to age 8 in the rear compared with passengers in the right front seat (RR=0.27, 95% CI 0.12-0.58 for 0-3 years, RR=0.55, 95% CI 0.30-0.98 for 4-8 years) but was higher for restrained 9-12-year-old children (RR=1.83, 95% CI 1.18-2.84). There was no evidence for a difference in risk of death in the rear vs. front seat for occupants ages 13-54, but there was some evidence for an increased relative risk of death for adults age 55 and older in the rear vs. passengers in the right front seat (RR=1.41, 95% CI 0.94-2.13), though we could not exclude the possibility of no difference. After controlling for occupant age and gender, the relative risk of death for restrained rear row occupants was significantly higher than that of front seat occupants in model year 2007 and newer vehicles and significantly higher in rear and right side impact crashes. CONCLUSIONS: Results of this study extend prior research on the relative safety of the rear seat compared with the front by examining a more contemporary fleet of vehicles. The rear row is primarily occupied by children and adolescents, but the variable relative risk of death in the rear compared with the front seat for occupants of different age groups highlights the challenges in providing optimal protection to a wide range of rear seat occupants. Findings of an elevated risk of death for rear row occupants, as compared with front row passengers, in the newest model year vehicles provides further evidence that rear seat safety is not keeping pace with advances in the front seat.

Factors affecting tether use and correct use in child restraint installations.

INTRODUCTION: Field studies show that top tethers go unused in half of forward-facing child restraint installations. METHOD: In this study, parent volunteers were asked to use the Lower Anchors and Tethers for Children (LATCH) to install child restraints in several vehicles to identify tether anchor characteristics that are associated with tether use. Thirty-seven volunteers were assigned to four groups. Each group tested two forward-facing child restraints in four of 16 vehicle models. Logistic regression models were used to identify predictors of tether use and correct use. RESULTS: Subjects used the tether in 89% of the 294 forward-facing child restraint installations and attached the tether correctly in 57% of the installations. Tethers were more likely to be used when the anchor was located on the rear deck as typically found in sedans compared with the seatback, floor, or roof. Tethers were less likely to be attached correctly when there was potentially confusing hardware present. No vehicle tether hardware characteristics or vehicle manual directions were associated specifically with correct tether routing and head restraint position. CONCLUSION: This study provides laboratory evidence that specific vehicle features are associated with tether use and correct use. PRACTICAL APPLICATIONS: Modifications to vehicles that make tether anchors easier to find and identify likely will result in increases in tether use and correct use.

Use of top tethers with forward-facing child restraints: observations and driver interviews.

OBJECTIVE: Despite the safety benefits, many parents do not use top tethers with forward-facing child restraints. Detailed information was collected about why parents are not using tethers. METHODS: The sample included 479 drivers who had forward-facing child restraints installed in passenger vehicles equipped with tether anchors. The survey was conducted primarily at shopping centers, recreation facilities, child care facilities, car seat check events, and health care facilities in mostly suburban areas surrounding Philadelphia, Washington, DC, Fredericksburg (VA), and Seattle. Drivers were surveyed about their knowledge and use of tethers and experience with child restraints. Tether use was observed to verify whether tethers were being used correctly. RESULTS: Fifty-six percent of forward-facing child restraints were installed with the tether; 39% were installed with the tether used correctly. The tether was used with 71% of LATCH lower anchor installations and 33% of seat belt installations. Drivers who installed child restraints without tethers most often said they did not know about the tether or how to use it. CONCLUSIONS: Although the tether use rate was slightly higher in the current research than in previous studies, many parents and caregivers still use forward-facing child restraints without attaching the tether. Because the main problem is lack of awareness of the tether or how to use it, public education should focus specifically on the safety benefits of tethers and how to use them. PRACTICAL APPLICATIONS: Information about why caregivers fail to use top tethers is potentially useful to child restraint manufacturers, child passenger safety technicians, and others who work with parents to improve motor vehicle safety.

Vehicle LATCH system features associated with correct child restraint installations.

OBJECTIVE: Lower anchors and tethers for children (LATCH) was intended to standardize the attachment between child restraints and vehicle seats. However, LATCH implementations vary, resulting in differences in ease of attachment of child restraint connectors. Identifying vehicle characteristics associated with correct child restraint installations can provide guidance for designing vehicle LATCH systems that increase correct child restraint installations. METHODS: The LATCH system and other relevant vehicle characteristics were documented in 98 top-selling 2010-2011 vehicles. These features, together with proposed LATCH usability recommendations from the International Organization for Standardization and Society of Automotive Engineers, were used to select 12 vehicles for volunteer testing with a range of LATCH system characteristics. Thirty-six volunteers were assigned to 4 groups; each group tested 3 vehicles, 4 child restraints (infant, rear-facing convertible, forward-facing convertible, and combination seat), and 2 installation methods (lower anchors and seat belt) in a split-plot experimental design. Mixed-effects logistic regression models were used to identify predictors of tight installation and correct lower anchor use. RESULTS: Vehicle survey results indicated that most vehicle manufacturers provide the minimum number of LATCH hardware locations required by regulation. Among 21 vehicles with a third row, 4 had no tether anchors and 11 had no lower anchors in the third row. Study volunteers correctly used the lower anchors in 60 percent of LATCH installations and used the top tether in 48 percent of forward-facing installations. When the tether was used, use was correct in 46 percent of trials (22% of all forward-facing installations). Only 13 percent of all trials had completely correct child restraint installation (correct use of lower anchors or seat belt, correct tether anchor use, tight seat installation, and correct installation angle). Tight installation was 3.3 times as likely with correct lower anchor use compared to trials with incorrect use. Three lower anchor characteristics were associated with rates of correct lower anchor use above 50 percent: clearance angle around the lower anchors greater than 54°, attachment forces less than 178 N, and anchor depth within the seat bight of less than 2 cm. Vehicles meeting all 3 criteria were 19 times as likely to have lower anchors used correctly compared to vehicles meeting none of the criteria. No vehicle features predicted either use of tethers or correct use of tethers. CONCLUSIONS: Vehicle LATCH systems that improve lower anchor accessibility could increase the rate of correct lower anchor use, but more research is needed to understand factors associated with tether use and correct use.

Effects of booster seat laws on injury risk among children in crashes.

OBJECTIVE: Belt-positioning booster seats have been shown to reduce injury risk among child passengers aged 4 to 8 in motor vehicle crashes. To encourage the use of booster seats, many states have enacted laws that require the use of either a child restraint with internal harness or a belt-positioning booster seat, but the specific age range covered by the laws varies by state. Previous studies have found evidence that booster seat laws are effective in reducing injury risk among children, but these studies primarily have included states with younger age requirements (e.g., ages 4-6) for booster seats. The objective of the present study was to examine the effectiveness of booster seat laws in several states that cover children through age 7 or 8. METHODS: Police-reported crash data from 5 states--Missouri, North Carolina, Pennsylvania, Wisconsin, and Wyoming--were used to compare population-based injury rates, restraint use, and seating position among children before and after booster seat laws. The pre-law period was comprised of the 2 calendar years prior to the year of enactment of the booster seat law, and the post-law period was comprised of the 2 calendar years after the year of the effective start of the booster seat law. Effectiveness estimates were adjusted using a comparison group of children aged 9 to 12 in the same states who were not covered by the booster seat laws. RESULTS: Among children in crashes who were affected by law changes in the 5 study states, the per capita rate of children using child safety seats (either a harnessed child restraint or booster seat) increased nearly 3 times, and the per capita rate of children riding in rear seats increased 6 percent after the booster seat laws were implemented. Booster seat laws were associated with a 5 percent reduction in the per capita rate of children who sustained injuries of any severity and a 17 percent reduction in the per capita rate of children who sustained fatal or incapacitating injuries. CONCLUSIONS: Results provide evidence that booster seat laws are effective in increasing the use of child safety seats, increasing the placement of children in rear seats, and reducing injuries, especially severe injuries, among children covered by the laws.

Crash avoidance potential of four large truck technologies.

OBJECTIVES: The objective of this paper was to estimate the maximum potential large truck crash reductions in the United States associated with each of four crash avoidance technologies: side view assist, forward collision warning/mitigation, lane departure warning/prevention, and vehicle stability control. Estimates accounted for limitations of current systems. METHODS: Crash records were extracted from the 2004-08 files of the National Automotive Sampling System General Estimates System (NASS GES) and the Fatality Analysis Reporting System (FARS). Crash descriptors such as location of damage on the vehicle, road characteristics, time of day, and precrash maneuvers were reviewed to determine whether the information or action provided by each technology potentially could have prevented the crash. RESULTS: Of the four technologies, side view assist had the greatest potential for preventing large truck crashes of any severity; the technology is potentially applicable to 39,000 crashes in the United States each year, including 2000 serious and moderate injury crashes and 79 fatal crashes. Vehicle stability control is another promising technology, with the potential to prevent or mitigate up to 31,000 crashes per year including more serious crashes--up to 7000 moderate-to-serious injury crashes and 439 fatal crashes per year. Vehicle stability control could prevent or mitigate up to 20 and 11 percent of moderate-to-serious injury and fatal large truck crashes, respectively. Forward collision warning has the potential to prevent as many as 31,000 crashes per year, including 3000 serious and moderate injury crashes and 115 fatal crashes. Finally, 10,000 large truck crashes annually were relevant to lane departure warning/prevention systems. Of these, 1000 involved serious and moderate injuries and 247 involved fatal injuries. CONCLUSIONS: There is great potential effectiveness for truck-based crash avoidance systems. However, it is yet to be determined how drivers will interact with the systems. Actual effectiveness of crash avoidance systems will not be known until sufficient real-world experience has been gained.

Crash avoidance potential of four passenger vehicle technologies.

OBJECTIVES: The objective was to update estimates of maximum potential crash reductions in the United States associated with each of four crash avoidance technologies: side view assist, forward collision warning/mitigation, lane departure warning/prevention, and adaptive headlights. Compared with previous estimates (Farmer, 2008), estimates in this study attempted to account for known limitations of current systems. METHODS: Crash records were extracted from the 2004-08 files of the National Automotive Sampling System General Estimates System (NASS GES) and the Fatality Analysis Reporting System (FARS). Crash descriptors such as vehicle damage location, road characteristics, time of day, and precrash maneuvers were reviewed to determine whether the information or action provided by each technology potentially could have prevented or mitigated the crash. RESULTS: Of the four crash avoidance technologies, forward collision warning/mitigation had the greatest potential for preventing crashes of any severity; the technology is potentially applicable to 1.2 million crashes in the United States each year, including 66,000 serious and moderate injury crashes and 879 fatal crashes. Lane departure warning/prevention systems appeared relevant to 179,000 crashes per year. Side view assist and adaptive headlights could prevent 395,000 and 142,000 crashes per year, respectively. Lane departure warning/prevention was relevant to the most fatal crashes, up to 7500 fatal crashes per year. A combination of all four current technologies potentially could prevent or mitigate (without double counting) up to 1,866,000 crashes each year, including 149,000 serious and moderate injury crashes and 10,238 fatal crashes. If forward collision warning were extended to detect objects, pedestrians, and bicyclists, it would be relevant to an additional 3868 unique fatal crashes. CONCLUSIONS: There is great potential effectiveness for vehicle-based crash avoidance systems. However, it is yet to be determined how drivers will interact with the systems. The actual effectiveness of these systems will not be known until sufficient real-world experience has been gained.

Observed use of tethers in forward-facing child restraint systems.

BACKGROUND: Use 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. OBJECTIVES: To obtain an updated estimate of top tether use. METHODS: Data on forward-facing child restraints were collected through an observational survey in the Washington DC metropolitan area during July-August 2010. The study sample included all forward-facing restraints that were installed in parked passenger vehicles and visible such that tether use could be observed. For each restraint, certified child passenger safety technicians collected information on the vehicle, seat row, restraint position, and tether. RESULTS: A total of 1321 cars, minivans, pickups, and sport utility vehicles, with a total of 1543 forward-facing child restraints, were observed. Tethers were used with 43.0% of all forward-facing child restraints. Tether use was similar (42.7-45.4%) among cars, minivans, and sport utility vehicles but lower (17.2%) for pickups. Tether use was higher (47.5%) for 2001 and newer vehicles, but dropped to 43.0% when only taut installations were considered. CONCLUSIONS: Despite LATCH education campaigns and the increased availability of tether anchors, observed tether use was less than 50%. Tether use was even lower in older vehicles, yet many children continue to travel in these vehicles. If tether anchors are unavailable, parents should be encouraged to retrofit vehicle seating positions. Because many child restraints are still installed with vehicle seat belts, efforts to educate parents on the importance of tether use regardless of installation method may be warranted.

Effectiveness of belt positioning booster seats: an updated assessment.

OBJECTIVE: The objective of this study was to provide an updated estimate of the effectiveness of belt-positioning booster (BPB) seats compared with seat belts alone in reducing the risk for injury for children aged 4 to 8 years. METHODS: Data were collected from a longitudinal study of children who were involved in crashes in 16 states and the District of Columbia from December 1, 1998, to November 30, 2007, with data collected via insurance claims records and a validated telephone survey. The study sample included children who were aged 4 to 8 years, seated in the rear rows of the vehicle, and restrained by either a seat belt or a BPB seat. Multivariable logistic regression was used to determine the odds of injury for those in BPB seats versus those in seat belts. Effects of crash direction and booster seat type were also explored. RESULTS: Complete interview data were obtained on 7151 children in 6591 crashes representing an estimated 120646 children in 116503 crashes in the study population. The adjusted relative risk for injury to children in BPB seats compared with those in seat belts was 0.55. CONCLUSIONS: This study reconfirms previous reports that BPB seats reduce the risk for injury in children aged 4 through 8 years. On the basis of these analyses, parents, pediatricians, and health educators should continue to recommend as best practice the use of BPB seats once a child outgrows a harness-based child restraint until he or she is at least 8 years of age.

Abdominal injuries in belt-positioning booster seats.

Previous studies have demonstrated that booster seats reduce the risk of abdominal injuries by improving the fit of the seat belt on young children and encouraging better posture and compatibility with the vehicle seat. Recently, several studies have reported cases of abdominal injuries in booster seated children questioning the protective effects of these restraints. The objective of this study was to examine cases of abdominal injuries in booster seated children through parametric modeling to gain a thorough understanding of the injury causation scenarios. The Partners for Child Passenger Safety and CIREN in-depth crash investigation databases were queried to identify children in belt-positioning booster seats with abdominal injuries. The injury causation scenarios for these injuries were delineated using the CIREN Biotab method. The cases were modeled, using MADYMO with variations in key parameters, to determine the ranges of loads and loading rates for the abdomen and thorax. A parametric study was completed examining the influence of pretensioners and load limiters on the injury metrics obtained. Query of the two databases revealed three cases involving abdominal injuries to booster seated children. Children in two of the cases sustained a thoracic injury (AIS 3/AIS 4) in addition to their abdominal injuries (AIS 2) and review of these cases pointed to the role of shoulder belt loading in the injury causation. Modeling of these cases revealed chest compressions and accelerations of 30-53 mm and 41-89 g, respectively and abdominal deflection and velocity of 7.0-13.3 mm and 1.2-2.2 m/s, respectively. Parametric study suggested that coupling shoulder belt load limiting and lap belt buckle pretensioning resulted in improved chest and abdominal metrics while reducing head excursion, indicating that these technologies may provide injury reduction potential to pediatric rear seat occupants.