Consumer experiences with crash avoidance feature repairs.

INTRODUCTION: Popularity of crash avoidance features is growing, but so too is confusion around how to repair them, how much repairs should cost, and who should pay for those repairs. This study's purpose was to capture how these issues are affecting consumers. METHOD: A total of 496 vehicle owners in the United States were surveyed online and by phone about their experiences repairing front crash prevention (n = 359), blind spot detection (n = 317), and/or driver assistance cameras (n = 348) equipped on their personal vehicles. RESULTS: Owners tended to have multiple reasons for repairs. Repairs due to vehicle (i.e., crash or windshield) damage corresponded with the greatest likelihood of post-repair issues, especially if calibration was performed, and higher out-of-pocket costs (possibly because of deductibles or other repair work). About half of respondents who had calibrations performed on features repaired because of vehicle damage reported persisting issues with the features after repair. Post-repair issues were more common for repairs performed at independent repairers than dealership service centers, yet similar feature calibration rates were reported for both types of repairers. More people went to dealership service centers than independent repairers, and these respondents were more likely to say they would return to this type of facility for a similar repair in the future. Although most repairers explained why repairs occurred, less than half of respondents said they completely understood the reasons given. CONCLUSIONS: There are new complications in the repair cycle affecting consumers. Post-repair issues are more prevalent than previously assumed, regardless of the crash avoidance feature repaired. PRACTICAL APPLICATIONS: Post-repair issues risk undermining consumer acceptance and the safety potential of critical features. Simplifying the repair process and establishing affordable and accessible centralized databases with repair specifications and instructions from the manufacturers would be a start to addressing industry-wide challenges.

Prevalence of distracted driving by driver characteristics in the United States.

INTRODUCTION: Distracted driving is a long-standing traffic safety concern, though common secondary tasks continually evolve. The goal of this study was to measure the prevalence of self-reported distracted driving behaviors, including activities made possible in recent years by smartphones. METHODS: We conducted a nationwide survey of 2,013 U.S. licensed drivers (ages 16 +). We created four aggregate distraction categories from 18 individual secondary tasks to estimate the proportion of drivers study-wide and by demographic characteristics belonging to each category, defined as those who regularly did (during most or all drives in the previous 30 days) one or more secondary task within each category. Logistic regression estimated the adjusted odds of drivers belonging to each aggregate distraction category by demographic characteristics. RESULTS: Sixty-five percent of drivers reported doing at least one of the 18 secondary tasks regularly, and half did at least one device-based task regularly in the past 30 days. Non-device task prevalence trended downward with age, while device-based task prevalence was consistent among younger drivers before declining beginning with age 35. Males (OR, 1.53; 95% CI, 1.16, 2.02), parents of children ages 18 and younger (OR, 1.47; 95% CI, 1.10, 1.96), and participants who drive in the gig economy (OR, 3.85; 95% CI, 2.73, 5.43) had higher adjusted odds of engaging in "modern" device-based distractions enabled by smartphones (e.g., making video calls, watching videos, using social media) than other drivers. Many drivers are using hands-free capabilities when available for tasks, but for some tasks more than others. CONCLUSIONS: Regular distracted driving is widespread with most behavior concentrated among drivers younger than age 50, though no age group or other demographic studied abstains. PRACTICAL APPLICATIONS: Stakeholders can use these findings to develop countermeasures for distracted driving by targeting specific secondary tasks and the demographics most likely to report regularly doing them.

What humanlike errors do autonomous vehicles need to avoid to maximize safety?

INTRODUCTION: The final failure in the causal chain of events in 94% of crashes is driver error. It is assumed most crashes will be prevented by autonomous vehicles (AVs), but AVs will still crash if they make the same mistakes as humans. By identifying the distribution of crashes among various contributing factors, this study provides guidance on the roles AVs must perform and errors they must avoid to realize their safety potential. METHOD: Using the NMVCCS database, five categories of driver-related contributing factors were assigned to crashes: (1) sensing/perceiving (i.e., not recognizing hazards); (2) predicting (i.e., misjudging behavior of other vehicles); (3) planning/deciding (i.e., poor decision-making behind traffic law adherence and defensive driving); (4) execution/performance (i.e., inappropriate vehicle control); and (5) incapacitation (i.e., alcohol-impaired or otherwise incapacitated driver). Assuming AVs would have superior perception and be incapable of incapacitation, we determined how many crashes would persist beyond those with incapacitation or exclusively sensing/perceiving factors. RESULTS: Thirty-three percent of crashes involved only sensing/perceiving factors (23%) or incapacitation (10%). If they could be prevented by AVs, 67% could remain, many with planning/deciding (41%), execution/performance (23%), and predicting (17%) factors. Crashes with planning/deciding factors often involved speeding (23%) or illegal maneuvers (15%). CONCLUSIONS: Errors in choosing evasive maneuvers, predicting actions of other road users, and traveling at speeds suitable for conditions will persist if designers program AVs to make errors similar to those of today's human drivers. Planning/deciding factors, such as speeding and disobeying traffic laws, reflect driver preferences, and AV design philosophies will need to be consistent with safety rather than occupant preferences when they conflict. Practical applications: This study illustrates the complex roles AVs will have to perform and the risks arising from occupant preferences that AV designers and regulators must address if AVs will realize their potential to eliminate most crashes.

Laboratory Reconstructions of Bicycle Helmet Damage: Investigation of Cyclist Head Impacts Using Oblique Impacts and Computed Tomography.

Although head injuries are common in cycling, exact conditions associated with cyclist head impacts are difficult to determine. Previous studies have attempted to reverse engineer cyclist head impacts by reconstructing bicycle helmet residual damage, but they have been limited by simplified damage assessment and testing. The present study seeks to enhance knowledge of cyclist head impact conditions by reconstructing helmet damage using advanced impact testing and damage quantification techniques. Damage to 18 helmets from cyclists treated in emergency departments was quantified using computed tomography and reconstructed using oblique impacts. Damage metrics were related to normal and tangential velocities from impact tests as well as peak linear accelerations (PLA) and peak rotational velocities (PRV) using case-specific regression models. Models then allowed original impact conditions and kinematics to be estimated for each case. Helmets were most frequently damaged at the front and sides, often near the rim. Concussion was the most common, non-superficial head injury. Normal velocity and PLA distributions were similar to previous studies, with median values of 3.4 m/s and 102.5 g. Associated tangential velocity and PRV medians were 3.8 m/s and 22.3 rad/s. Results can inform future oblique impact testing conditions, enabling improved helmet evaluation and design.

Not all protected bike lanes are the same: Infrastructure and risk of cyclist collisions and falls leading to emergency department visits in three U.S. cities.

OBJECTIVE: Protected bike lanes separated from the roadway by physical barriers are relatively new in the United States. This study examined the risk of collisions or falls leading to emergency department visits associated with bicycle facilities (e.g., protected bike lanes, conventional bike lanes demarcated by painted lines, sharrows) and other roadway characteristics in three U.S. cities. METHODS: We prospectively recruited 604 patients from emergency departments in Washington, DC; New York City; and Portland, Oregon during 2015-2017 who fell or crashed while cycling. We used a case-crossover design and conditional logistic regression to compare each fall or crash site with a randomly selected control location along the route leading to the incident. We validated the presence of site characteristics described by participants using Google Street View and city GIS inventories of bicycle facilities and other roadway features. RESULTS: Compared with cycling on lanes of major roads without bicycle facilities, the risk of crashing or falling was lower on conventional bike lanes (adjusted OR = 0.53; 95 % CI = 0.33, 0.86) and local roads with (adjusted OR = 0.31; 95 % CI = 0.13, 0.75) or without bicycle facilities or traffic calming (adjusted OR = 0.39; 95 % CI = 0.23, 0.65). Protected bike lanes with heavy separation (tall, continuous barriers or grade and horizontal separation) were associated with lower risk (adjusted OR = 0.10; 95 % CI = 0.01, 0.95), but those with lighter separation (e.g., parked cars, posts, low curb) had similar risk to major roads when one way (adjusted OR = 1.19; 95 % CI = 0.46, 3.10) and higher risk when they were two way (adjusted OR = 11.38; 95 % CI = 1.40, 92.57); this risk increase was primarily driven by one lane in Washington. Risk increased in the presence of streetcar or train tracks relative to their absence (adjusted OR = 26.65; 95 % CI = 3.23, 220.17), on downhill relative to flat grades (adjusted OR = 1.92; 95 % CI = 1.38, 2.66), and when temporary features like construction or parked cars blocked the cyclist's path relative to when they did not (adjusted OR = 2.23; 95 % CI = 1.46, 3.39). CONCLUSIONS: Certain bicycle facilities are safer for cyclists than riding on major roads. Protected bike lanes vary in how well they shield riders from crashes and falls. Heavier separation, less frequent intersections with roads and driveways, and less complexity appear to contribute to reduced risk in protected bike lanes. Future research should systematically examine the characteristics that reduce risk in protected lanes to guide design. Planners should minimize conflict points when choosing where to place protected bike lanes and should implement countermeasures to increase visibility at these locations when they are unavoidable.

Development of the STAR Evaluation System for Assessing Bicycle Helmet Protective Performance.

Cycling is a leading cause of mild traumatic brain injury in the US. While bicycle helmets help protect cyclists who crash, limited biomechanical data exist differentiating helmet protective capabilities. This paper describes the development of a bicycle helmet evaluation scheme based in real-world cyclist accidents and brain injury mechanisms. Thirty helmet models were subjected to oblique impacts at six helmet locations and two impact velocities. The summation of tests for the analysis of risk (STAR) equation, which condenses helmet performance from a range of tests into a single value, was used to summarize measured linear and rotational head kinematics in the context of concussion risk. STAR values varied between helmets (10.9-25.3), with lower values representing superior protection. Road helmets produced lower STAR values than urban helmets. Helmets with slip planes produced lower STAR values than helmets without. This bicycle helmet evaluation protocol can educate consumers on the relative impact performance of various helmets and stimulate safer helmet design.

Characteristics of rear-end crashes involving passenger vehicles with automatic emergency braking.

Objectives: Automatic emergency braking (AEB) is a proven effective countermeasure for preventing front-to-rear crashes, but it has not yet fully lived up to its estimated potential. This study identified the types of rear-end crashes in which striking vehicles with AEB are overrepresented to determine whether the system is more effective in some situations than in others, so that additional opportunities for increasing AEB effectiveness might be explored. Methods: Rear-end crash involvements were extracted from 23 U.S. states during 2009-2016 for striking passenger vehicles with and without AEB among models where the system was optional. Logistic regression was used to examine the odds that rear-end crashes with various characteristics involved a striking vehicle with AEB, controlling for driver and vehicle features. Results: Striking vehicles were significantly more likely to have AEB in crashes where the striking vehicle was turning relative to when it was moving straight (odds ratio [OR] = 2.35; 95% confidence interval [CI], 1.76, 3.13); when the struck vehicle was turning (OR = 1.66; 95% CI, 1.25, 2.21) or changing lanes (OR = 2.05; 95% CI, 1.13, 3.72) relative to when it was slowing or stopped; when the struck vehicle was not a passenger vehicle or was a special use vehicle relative to a car (OR = 1.61; 95% CI, 1.01, 2.55); on snowy or icy roads relative to dry roads (OR = 1.83; 95% CI, 1.16, 2.86); or on roads with speed limits of 70+ mph relative to those with 40 to 45 mph speed limits (OR = 1.49; 95% CI, 1.10, 2.03). Overall, 25.3% of crashes where the striking vehicle had AEB had at least one of these overrepresented characteristics, compared with 15.9% of strikes by vehicles without AEB. Conclusions: The typical rear-end crash occurs when 2 passenger vehicles are proceeding in line, on a dry road, and at lower speeds. Because atypical crash circumstances are overrepresented among rear-end crashes by striking vehicles with AEB, it appears that the system is doing a better job of preventing the more typical crash scenario. Consumer information testing programs of AEB use a test configuration that models the typical rear-end crash type. Testing programs promoting good AEB performance in crash circumstances where vehicles with AEB are overrepresented could guide future development of AEB systems that perform well in these additional rear-end collision scenarios.

Differences in the protective capabilities of bicycle helmets in real-world and standard-specified impact scenarios.

OBJECTIVE: The purpose of this study was to investigate relative differences in impact attenuation capabilities of bicycle helmets under real-world impact conditions and safety standard-specified conditions using a standard rig. METHODS: A Consumer Product Safety Commission (CPSC) test rig was used to impact 10 helmet models of varied design. Impact configurations included 2 locations and 2 velocities. A frontal rim location (inferior to the standard-defined test area) and a temporal location were selected to reflect common cyclist impacts. An impact velocity of 3.4 m/s, an average normal impact velocity in cyclist accidents, was selected, as well as the CPSC standard velocity of 6.2 m/s. Four samples per helmet model were subjected to each of the 4 impact configurations once (randomized test order per sample), resulting in 160 drop tests. Peak linear acceleration (PLA) and head injury criterion (HIC)-based Abbreviated Injury Scale (AIS) ≥ 4 brain injury risk were determined and compared across helmets and impact configurations using analysis of variance. Other impact characteristics such as duration, effective liner stiffness, and energy dissipated were also calculated from acceleration data. RESULTS: Helmet performance varied significantly between models. PLA ranged from 78 to 169 g at 3.4 m/s (0-2% AIS ≥ 4 brain injury risk) and 165-432 g (10-100% risk) at 6.2 m/s. Temporal impacts resulted in higher PLAs than frontal impacts, likely due to increased effective liner stiffness. However, 2 helmets exceeded the CPSC pass-fail threshold (300 g) at the frontal rim location, producing >70% risk. Force-displacement curves suggest that bottoming-out occurred in these impacts. Aside from bottoming-out cases, helmets that performed worse in one impact configuration tended to perform worse in others, with non-road-style helmets among the worst. CONCLUSIONS: The 10 bicycle helmets tested produced considerable differences in their protective capabilities under both real-world and standard-specified conditions on the CPSC rig. Risk of severe brain injury varied widely between helmets at the standard impact velocity, whereas the common, lower severity impacts produced PLAs associated with concussion. Helmets of a nonroad style generally performed worse across configuration. The temporal location produced higher risks for most helmets, although some helmets were found to offer inadequate protection at the helmet rim. Because this is a commonly impacted location in cyclist accidents, there may be benefit to expanding the testable area in standards to include the rim. Results from this study demonstrate the value in testing nonstandard conditions and can be used to inform standards testing and helmet design.

Prevalence of driver physical factors leading to unintentional lane departure crashes.

OBJECTIVE: Some lane-keeping assist systems in development and production provide autonomous braking and steering to correct unintentional lane drift but otherwise require drivers to fully control their vehicles. The goal of this study was to quantify the proportion of drivers involved in unintentional lane drift crashes who would be unable to regain control of their vehicles to inform the design of such systems. METHODS: The NHTSA's National Motor Vehicle Crash Causation Survey collected in-depth, on-scene data for a nationally representative sample of 5,470 U.S. police-reported passenger vehicle crashes during 2005-2007 that occurred between 6 a.m. and midnight and for which emergency medical services were dispatched. The physical states of drivers involved in the 631 lane drift crashes in the sample, which represented 259,034 crashes nationally, were characterized. RESULTS: Thirty-four percent of drivers who crashed because they drifted from their lanes were sleeping or otherwise incapacitated. These drivers would be unlikely to regain full control of their vehicles if an active safety system prevented their initial drift. An additional 13% of these drivers had a nonincapacitating medical issue, blood alcohol concentration (BAC) ≥ 0.08%, or other physical factor that may not allow them to regain full vehicle control. When crashes involved serious or fatal injuries, 42% of drivers who drifted were sleeping or otherwise incapacitated, and an additional 14% were impacted by a nonincapacitating medical issue, BAC ≥ 0.08%, or other physical factor. CONCLUSIONS: Designers of active safety systems that provide autonomous lateral control should consider that a substantial proportion of drivers at risk of lane drift crashes are incapacitated. Systems that provide only transient corrective action may not ultimately prevent lane departure crashes for these drivers, and drivers who do avoid lane drift crashes because of these systems may be at high risk of other types of crashes when they attempt to regain control. Active lane-keeping assist systems may need to be combined with in-vehicle driver monitoring to identify incapacitated drivers and safely remove them from the roadway if the systems are to reach their maximum potential benefit.

IIHS head restraint ratings and insurance injury claim rates.

OBJECTIVES: The Insurance Institute for Highway Safety (IIHS) rates front seat/head restraint designs using a combination of static and dynamic measurements following RCAR-IIWPG procedures. The purpose of this study was to determine whether vehicles with better IIHS-rated seats/head restraints had lower injury risk in rear-end collisions and how the effect of better rated seats interacted with driver gender and age. METHODS: The presence of an associated insurance injury claim was determined for rear-impact crashes using 2001-2014 model year cars and SUVs. Logistic regression was used to compare injury risk for vehicles with good, acceptable, and marginal IIHS-rated seats/head restraints with poor-rated seats/head restraints. Analyses were run by gender and driver age and also by the rate of more severe injury claims. RESULTS: Injury rates were 11.2% lower for vehicles with seats/head restraints rated good compared to vehicles with seats/head restraints rated poor. The percentage reduction for good- versus poor-rated seats was greater for females (12.7%) than males (8.9%). Comparing good- with poor-rated seats, driver ages 15-24 had the largest reduction at 19.8%, followed by 10.7% for driver ages 45-64 and 10.4% for driver ages 25-44. CONCLUSIONS: Seats/head restraints with better IIHS ratings are associated with lower injury rates in rear-impact collisions than seats rated poor. The reductions in injury rates were strongest for females and for young-to-middle-age drivers. The strong reductions in injury rates for these groups are encouraging given their high initial injury rates.

Structural Design Strategies for Improved Small Overlap Crashworthiness Performance.

In 2012, the Insurance Institute for Highway Safety (IIHS) began a 64 km/h small overlap frontal crash test consumer information test program. Thirteen automakers already have redesigned models to improve test performance. One or more distinct strategies are evident in these redesigns: reinforcement of the occupant compartment, use of energy-absorbing fender structures, and the addition of engagement structures to induce vehicle lateral translation. Each strategy influences vehicle kinematics, posing additional challenges for the restraint systems. The objective of this two-part study was to examine how vehicles were modified to improve small overlap test performance and then to examine how these modifications affect dummy response and restraint system performance. Among eight models tested before and after design changes, occupant compartment intrusion reductions ranged from 6 cm to 45 cm, with the highest reductions observed in models with the largest number of modifications. All redesigns included additional occupant compartment reinforcement, one-third added structures to engage the barrier, and two modified a shotgun load path. Designs with engagement structures produced greater glance-off from the barrier and exhibited lower delta Vs but experienced more lateral outboard motion of the dummy. Designs with heavy reinforcement of the occupant compartment had higher vehicle accelerations and delta V. In three cases, these apparent trade-offs were not well addressed by concurrent changes in restraint systems and resulted in increased injury risk compared with the original tests. Among the 36 models tested after design changes, the extent of design changes correlated to structural performance. Half of the vehicles with the lowest intrusion levels incorporated aspects of all three design strategies. Vehicle kinematics and dummy and restraint system characteristics were similar to those observed in the before/after pairs. Different combinations of structural improvement strategies for improving small overlap test performance were found to be effective in reducing occupant compartment intrusion and improving dummy kinematics in the IIHS small overlap test with modest weight increase.

Development of a frontal small overlap crashworthiness evaluation test.

OBJECTIVES: Small overlap frontal crashes are those in which crash forces are applied outboard of the vehicle's longitudinal frame rails. In-depth analyses of crashes indicate that such crashes account for a significant proportion of frontal crashes with seriously injured occupants. The objective of this research was to evaluate possible barrier crash tests that could be used to evaluate the crashworthiness of vehicles across a spectrum of small overlap crash types. METHODS: Sixteen full-scale vehicle tests were conducted using 3 midsize passenger vehicles in up to 6 different test configurations, including vehicle-to-vehicle and barrier tests. All vehicles were tested at 64 km/h with an instrumented Hybrid III midsize male driver dummy. RESULTS: All test configurations resulted in primary loading of the wheel, suspension system, and hinge pillar. Vehicles underwent substantial lateral movement during the crash, which varied by crash configuration. The occupant compartments had significant intrusion, particularly to the most outboard structures. Inboard movement of the steering wheel in combination with outboard movement of the dummies (due to the lateral vehicle motion) caused limited interaction with the frontal air bag in most cases. CONCLUSIONS: When assessing overall crashworthiness (based on injury measures, structural deformation, and occupant kinematics), one vehicle had superior performance in each crash configuration. This was confirmation that the countermeasures benefiting performance in a single small overlap test also will provide a benefit in other crash configurations. Based on these test results, the Insurance Institute for Highway Safety has developed a small overlap crashworthiness evaluation with the following characteristics: a rigid flat barrier with a 150-mm corner radius, 25 percent overlap, 64 km/h test speed, and a Hybrid III midsize male driver dummy.

Comparison of Hybrid III and THOR dummies in paired small overlap tests.

The Insurance Institute for Highway Safety (IIHS) is investigating small overlap crash test procedures for a possible consumer information program. Analysis of real-world small overlap crashes found a strong relationship between serious head and chest injuries and occupant compartment intrusion. The main sources of serious head injuries were from the A-pillar, dash panel, or door structure, suggesting head trajectories forward and outboard possibly bypassing the airbag. Chest injuries mainly were from steering wheel intrusion and seat belt loading. In developing this program, two test dummies were evaluated for predicting occupant injury risk: midsize male Hybrid III and THOR. In the collinear small overlap crash tests conducted here, results from the two dummies were similar. Both predicted a low risk of injury to the head and chest and sometimes a high risk of injury to the lower extremities. Head and torso kinematics also were similar between dummies. Other test scenarios might show larger differences between the dummies.

Volvo and Infiniti drivers' experiences with select crash avoidance technologies.

OBJECTIVES: Vehicle-based crash avoidance systems can potentially reduce crashes, but success depends on driver acceptance and understanding. This study gauged driver use, experience, and acceptance among early adopters of select technologies. METHODS: Telephone interviews were conducted in early 2009 with 380 owners of Volvo vehicles equipped with forward collision warning with autobrake, lane departure warning, side-view assist, and/or active bi-xenon headlights and 485 owners of Infiniti vehicles with lane departure warning/prevention. RESULTS: Most owners kept systems turned on most of the time, especially forward collision warning with autobrake and side-view assist. The exception was lane departure prevention; many owners were unaware they had it, and the system must be activated each time the vehicle is started. Most owners reported being safer with the technologies and would want them again on their next vehicles. Perceived false or unnecessary warnings were fairly common, particularly with side-view assist. Some systems were annoying, especially lane departure warning. Many owners reported safer driving behaviors such as greater use of turn signals (lane departure warning), increased following distance (forward collision warning), and checking side mirrors more frequently (side-view assist), but some reported driving faster at night (active headlights). CONCLUSIONS: Despite some unnecessary or annoying warnings, most Volvo and Infiniti owners use crash avoidance systems most of the time. Among early adopters, the first requirement of effective warning systems (that owners use the technology) seems largely met. Systems requiring activation by drivers for each trip are used less often. Owner experience with the latest technologies from other automobile manufacturers should be studied, as well as for vehicles on which technologies are standard (versus optional) equipment. The effectiveness of technologies in preventing and mitigating crashes and injuries, and user acceptance of interfaces, should be examined as more vehicles with advanced technologies penetrate the fleet.

Preventing minor neck injuries in rear crashes--forty years of progress.

OBJECTIVE: This article offers a historical review of vehicle design measures that have been implemented to reduce the risk of neck injuries to the occupants of rear struck vehicles. METHODS: The literature on regulations, consumer information programs, and efforts by vehicle manufacturers to address whiplash injuries is summarized along with studies evaluating the efficacy of the resulting vehicle design changes. RESULTS: Vehicle designs and, in particular, the designs of seats and head restraints have changed considerably over the last 40 years. With varying degrees, these changes seem to be reducing the likelihood that occupants in rear struck vehicles will suffer neck injuries in such crashes. CONCLUSIONS: Vehicle design has influenced the risk of neck injuries in crashes, and future design changes offer potential for further risk reduction.

Front air bag nondeployments in frontal crashes fatal to drivers or right-front passengers.

OBJECTIVE: Public concern has arisen about the reliability of front air bags because Fatality Analysis Reporting System (FARS) data indicate many nondeployed air bags in fatal frontal crashes. However, the accuracy of air bag deployment, the variable in question, is uncertain. This study aimed to provide more certain estimates of nondeployment incidence in fatal frontal crashes. METHODS: Fatally injured passenger vehicle drivers and right-front passengers in frontal crashes were identified in two U.S. databases for calendar years 1998-2006 and model years 1994-2006: FARS, a census of police-reported fatal crashes on public roads, and National Automotive Sampling System/Crashworthiness Data System (NASS/CDS), a probability sample of tow-away crashes. NASS/CDS contains subsets of fatal crashes in FARS and collects detailed data using crash investigators. Front air bag deployment coding for front-seat occupant fatalities was compared in FARS and NASS/CDS, and case reviews were conducted. RESULTS: Among FARS frontal deaths with available deployment status (N = 43,169), front air bags were coded as not deployed for 18 percent of front occupants. In comparison, NASS/CDS (N = 628) reported 9 percent (weighted estimate) nondeployment among front occupants killed. Among crashes common to both databases, NASS/CDS reported deployments for 45 percent of front occupant deaths for which FARS had coded nondeployments. Detailed case reviews of NASS/CDS crashes indicated highly accurate coding for deployment status. Based on this case review, 8 percent (weighted estimate) of front occupant deaths in frontal crashes appeared to involve air bag nondeployments; 1-2 percent of front occupant deaths represented potential system failures where deployments would have been expected. Air bag deployments appeared unwarranted in most nondeployments based on crash characteristics. DISCUSSION: FARS data overstate the magnitude of the problem of air bag deployment failures; steps should be taken to improve coding. There are inherent uncertainties in judgments about whether or not air bags would be expected to deploy in some crashes. Continued monitoring of air bag performance is warranted.

Roof strength and injury risk in rollover crashes.

OBJECTIVE: Previous studies have reported that roof strength as measured in FMVSS 216 is unrelated to occupant injury risk in actual rollovers. However, those studies did not control for important confounding factors. The present study reevaluated roof strength and injury risk using a single class of vehicles with similar driver and vehicle usage characteristics in the expectation that some potential confounders will be controlled by this focused analysis. Alternative roof strength measures also were examined in case strength-to-weight ratio (SWR) at 5 inches, the measure in FMVSS 216, is not the best measure. METHODS: Eleven midsize SUV roof designs were crushed according to FMVSS 216 protocol. Force was measured continuously, and the maximum force and the amount of energy used to achieve crush of 2, 5, and 10 inches were recorded; these six measures of roof strength were evaluated both directly and after normalization for vehicle weight. After controlling for other potentially confounding variables, logistic regression models estimated the effect of each of the twelve roof strength measures on risk of fatal or incapacitating injuries to drivers in single-vehicle rollover crashes. Crash data were obtained from fourteen states. RESULTS: All roof strength measures correlated inversely, and similarly, with risk of fatal/incapacitating injury in single-vehicle rollovers. Across all states, 12 percent of drivers sustained fatal/incapacitating injuries, but individual state rates varied from 6 to 24 percent. Among available variables, only state substantially affected the estimated effect of roof strength; it was kept in the final models with roof strength, driver age, and static stability factor (SSF). Driver age was retained because it had a significant effect on injury outcome and SSF was retained for theoretical reasons. This model estimated that a one-unit increase in strength-to-weight ratio (SWR) within 5 inches of crush was associated with 24 percent lower risk of fatal/incapacitating injury (95% CI: 15-33). Ejection was lower by 41 percent (95% CI: 30-51), and injury risk among nonejected occupants was lower by 16 percent (95% CI: 3-29). CONCLUSIONS: The FMVSS 216 measure of roof strength related strongly to occupant protection in real-world rollover crashes in this study, which restricted analysis to vehicles with reasonably homogeneous driver and usage characteristics and accounted for state variation in injury rates. Further research should determine whether these results generalize to other vehicle types with different drivers and rollover risk. Research should also focus on factors other than roof strength, because even large increases in roof strength would leave many rollover crash deaths unaffected.

Relationship of dynamic seat ratings to real-world neck injury rates.

OBJECTIVES: The Insurance Institute for Highway Safety assigns consumer safety ratings to passenger vehicle seats based on laboratory sled tests that simulate rear-end collisions. The purpose of this research was to determine how well these ratings correlate to driver neck injury risk in real-world crashes. METHODS: Insurance claims for cars and SUVs struck in the rear by the front of another passenger vehicle were examined for evidence of driver neck injury. Logistic regression was used to compare neck injury rates for vehicles with different seat ratings while controlling for other important variables. RESULTS: Driver neck injury rates were 15% lower for vehicles with seats rated good compared with vehicles with seats rated poor. Rates of driver neck injuries lasting 3 months or more were 35% lower for vehicles with seats rated good compared with vehicles with seats rated poor. CONCLUSIONS: Seat/head restraints that perform better in dynamic sled tests have lower risk of neck injury than seats that rate poor, especially when considering long-term injuries. However, the relationship of dynamic seat ratings to neck injury rates is not linear. Further research is needed to determine whether the criteria for rating seats can be amended so as to be more uniformly predictive of real-world neck injury.