Jessica S. Jermakian

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.

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.

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.

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.

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.

Public Opinion, Traffic Performance, the Environment, and Safety After Construction of Double-Lane Roundabouts

This study evaluated the impact of double-lane roundabout conversions on public attitudes, traffic performance, the environment, and safety at two intersections near Bellingham, Washington, and evaluated whether older drivers avoided the roundabouts by taking an alternative route. Driver support for the roundabouts increased from 34% before construction to 70% at 1 year after construction. At 1 year after construction, more than 40% of drivers did not believe the signs and pavement markings adequately conveyed information about appropriate speeds, right-of-way rules, and navigation of the roundabouts in the presence of large trucks. After other roadway changes were accounted for, substantial declines in the delays and queue lengths on minor roads, the proportion of queued vehicles, fuel consumption, and vehicle emissions were attributed to the roundabout conversions. Analyses of crash rates per million entering vehicles found that the roundabout conversions were associated with reduced rates of injury and fatal crashes combined and increased rates of property-damage-only crashes. Only the increase in the property-damage-only crash rate at one roundabout was significant. The odds that drivers age 70 years and older traveled the study corridor instead of an alternative route after the roundabout conversions were 0.32 times the odds before the conversions. These findings are generally consistent with prior research finding substantial traffic, environmental, and injury reduction benefits of single-lane roundabouts. However, the greater complexity of double-lane roundabouts may present challenges, as some confusion persisted 1 year after construction, evidence that some older drivers may have taken an alternative route to avoid them was found, and the rates of property-damage-only crashes increased.

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 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.

Survey of LATCH vehicle hardware

Ninety-eight 2010–2011 model year vehicles were surveyed to evaluate the usability of hardware known as Lower Anchors and Tethers for Children, or LATCH, required by US FMVSS 225. Most vehicles do not provide LATCH hardware beyond the minimum number of required seating positions. Only seven vehicles had three sets of LATCH hardware in the second row. In 21 vehicles with third rows, four had no tether anchors and 11 had no lower anchors in the third row. Relative to proposed the Society of Automotive Engineers (SAE) recommendations, 59 vehicles met the recommended lower attachment force of 75 N or less but only 2 vehicles met the recommended clearance angle of at least 75º. The depth of lower anchors relative to the bight was less than 2 cm in 28 vehicles, 2–4 cm in 34 vehicles and greater than 4 cm in 36 vehicles. Most tether anchors were on the seat back (42) or rear filler panel (35).