The Effects of Vehicle Redesign on the Risk of Driver Death.

OBJECTIVES: This study updates a 2006 report that estimated the historical effects of vehicle design changes on driver fatality rates in the United States, separate from the effects of environmental and driver behavior changes during the same period. In addition to extending the period covered by 8 years, this study estimated the effect of design changes by model year and vehicle type. METHODS: Driver death rates for consecutive model years of vehicle models without design changes were used to estimate the vehicle aging effect and the death rates that would have been expected if the entire fleet had remained unchanged from the 1985 calendar year. These calendar year estimates are taken to be the combined effect of road environment and motorist behavioral changes, with the difference between them and the actual calendar year driver fatality rates reflecting the effect of changes in vehicle design and distribution of vehicle types. The effects of vehicle design changes by model year were estimated for cars, SUVs, and pickups by computing driver death rates for model years 1984-2009 during each of their first 3 full calendar years of exposure and comparing with the expected rates if there had been no design changes. RESULTS: As reported in the 2006 study, had there been no changes in the vehicle fleet, driver death risk would have declined during calendar years 1985-1993 and then slowly increased from 1993 to 2004. The updated results indicate that the gradual increase would have continued through 2006, after which driver fatality rates again would have declined through 2012. Overall, it is estimated that there were 7,700 fewer driver deaths in 2012 than there would have been had vehicle designs not changed. Cars were the first vehicle type whose design safety generally exceeded that of the 1984 model year (starting in model year 1996), followed by SUVs (1998 models) and pickups (2002 models). By the 2009 model year, car driver fatality risk had declined 51% from its high in 1994, pickup driver fatality risk had declined 61% from its high in 1988, and SUV risk had declined 79% from its high in 1988. The risk of driver death in 2009 model passenger vehicles was 8% lower than that in 2008 models and about half that in 1984 models. CONCLUSIONS: Changes in vehicles, whether from government regulations and consumer testing that led to advanced safety designs or from other factors such as consumer demand for different sizes and types of vehicles, have been key contributors to the decline in U.S. motor vehicle occupant crash death rates since the mid-1990s. Since the early 1990s, environmental and behavioral risk factors have not shown similar improvement, until the recession of 2007, even though there are many empirically proven countermeasures that have been inadequately applied.

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.

IIHS side crash test ratings and occupant death risk in real-world crashes.

OBJECTIVE: To evaluate how well the Insurance Institute for Highway Safety (IIHS) side crash test ratings predict real-world occupant death risk in side-impact crashes. METHODS: The IIHS has been evaluating passenger vehicle side crashworthiness since 2003. In the IIHS side crash test, a vehicle is impacted perpendicularly on the driver's side by a moving deformable barrier simulating a typical sport utility vehicle (SUV) or pickup. Injury ratings are computed for the head/neck, torso, and pelvis/leg, and vehicles are rated based on their ability to protect occupants' heads and resist occupant compartment intrusion. Component ratings are combined into an overall rating of good, acceptable, marginal, or poor. A driver-only rating was recalculated by omitting rear passenger dummy data. Data were extracted from the Fatality Analysis Reporting System (FARS) and National Automotive Sampling System/General Estimates System (NASS/GES) for the years 2000-2009. Analyses were restricted to vehicles with driver side air bags with head and torso protection as standard features. The risk of driver death was computed as the number of drivers killed (FARS) divided by the number involved (NASS/GES) in left-side impacts and was modeled using logistic regression to control for the effects of driver age and gender and vehicle type and curb weight. Death rates per million registered vehicle years were computed for all outboard occupants and compared by overall rating. RESULTS: Based on the driver-only rating, drivers of vehicles rated good were 70 percent less likely to die when involved in left-side crashes than drivers of vehicles rated poor, after controlling for driver and vehicle factors. Compared with vehicles rated poor, driver death risk was 64 percent lower for vehicles rated acceptable and 49 percent lower for vehicles rated marginal. All 3 results were statistically significant. Among components, vehicle structure rating exhibited the strongest relationship with driver death risk. The vehicle registration-based results for drivers were similar, suggesting that the benefit was not due to differences in crash risk. The same pattern of results held for outboard occupants in nearside crashes per million registered vehicle years and, with the exception of marginally rated vehicles, also held for other crash types. CONCLUSIONS: Results show that IIHS side crash test ratings encourage designs that improve crash protection in meaningful ways beyond encouraging head protection side air bags, particularly by promoting vehicle structures that limit occupant compartment intrusion. Results further highlight the need for a strong occupant compartment and its influence in all types of crashes.

Cell phone use while driving and attributable crash risk.

OBJECTIVES: Prior research has estimated that crash risk is 4 times higher when talking on a cell phone versus not talking. The objectives of this study were to estimate the extent to which drivers talk on cell phones while driving and to compute the implied annual number of crashes that could have been avoided if driver cell phone use were restricted. METHODS: A national survey of approximately 1200 U.S. drivers was conducted. Respondents were asked to approximate the amount of time spent driving during a given day, number of cell phone calls made or received, and amount of driving time spent talking on a cell phone. Population attributable risk (PAR) was computed for each combination of driver gender, driver age, day of week, and time of day. These were multiplied by the corresponding crash counts to estimate the number of crashes that could have been avoided. RESULTS: On average, drivers were talking on cell phones approximately 7 percent of the time while driving. Rates were higher on weekdays (8%), in the afternoon and evening (8%), and for drivers younger than 30 (16%). Based on these use rates, restricting cell phones while driving could have prevented an estimated 22 percent (i.e., 1.3 million) of the crashes in 2008. CONCLUSIONS: Although increased rates of cell phone use while driving should be leading to increased crash rates, crash rates have been declining. Reasons for this paradox are unclear. One possibility is that the increase in cell phone use and crash risk due to cell phone use have been overestimated. Another possibility is that cell phone use has supplanted other driving distractions that were similarly hazardous.

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.

Making the most of the worst-case scenario: should belt-positioning booster seats be used in lap-belt-only seating positions?

OBJECTIVE: Examine real-world crash injury data to determine whether children seated with lap belts only are better protected with or without belt-positioning booster seats. METHODS: Crash injury rates among booster-age children were examined for three restraint categories: lap belt only, belt-positioning booster seat with lap belt, and booster seat with lap/shoulder belt. Data were drawn from the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) and the Partners for Child Passenger Safety (PCPS) crash surveillance system for years 1997-2006 and 1998-2006, respectively. Main outcome measures were the percentage of crash-involved booster-age children with moderate or greater injury (maximum abbreviated injury score [MAIS] 2+). RESULTS: The estimated risk of MAIS 2+ injury among children restrained with lap belts and boosters was 0.12 percent (NASS-CDS) and 0.96 percent (PCPS), compared with 1.21 and 1.74 percent, respectively, for lap belts only. This difference was not significant due to small numbers of children in lap belts with boosters. In PCPS, children restrained by lap/shoulder belts and boosters had lower injury risk than children restrained by lap belts, with or without boosters. CONCLUSIONS: Although data for children secured in lap belts with boosters are limited, the results suggest that boosters are not harmful. This finding is inconsistent with the current recommendation that booster seats not be used when children must be buckled with lap belts only. Data also confirm that booster seats with lap/shoulder belts remain the optimal protection for booster-age children.

Caution: a comment on Alena Erke's red light for red-light cameras? A meta-analysis of the effects of red-light cameras on crashes.

In Red Light for Red-Light Cameras?, Alena Erke concludes that "... on the whole, redlight cameras do not seem to be a successful safety measure." Although Erke's survey of the literature appears to have been comprehensive, her review of the studies was not critical. She appears to have accepted the authors' descriptions of their analyses rather than providing readers with her own considered opinion of how valid those analyses were and what their true implications might be. For the meta-analysis leading to her final conclusion, Erke combines data from two questionable studies with three other "well-controlled" studies. Non-peer-reviewed studies received substantial statistical weight in the meta-analysis. These problems likely produce misleading results. If the highway safety field is to succeed in identifying for policymakers those strategies that are most likely to reduce the human tragedy of motor vehicle crashes, we need first to focus on conducting valid research and analysis. Adding precision to the estimated benefits of those strategies through meta-analysis is important, but secondary, and cannot replace the function of a systematic and critical review.

Trends over time in the risk of driver death: what if vehicle designs had not improved?

OBJECTIVES: Passenger vehicle driver death rates per million vehicle registrations declined steadily during calendar years 1985-2004. The present study sought to separate the effect of vehicle design changes from this trend. METHODS: Restricting the trend to a fixed set of model years removed the vehicle design effects, but there were still effects due to vehicle aging. Risk of driver death was found to increase each year vehicles aged, probably due to changes in vehicle use patterns. RESULTS: After separating out the vehicle design effects and making adjustments for the vehicle age effects, a different picture emerged of trends in death rates over time. Absent the vehicle design changes, the historical decline in driver fatality risk would have ended in 1993, with risk climbing ever since. This underlying trend has been obscured by changes in the vehicle fleet. CONCLUSIONS: The push for vehicle improvements has been worthwhile and can be credited with saving thousands of lives. However, the analysis shows that the gains in occupant protection from vehicle design improvements have been offset partially by an increasingly risky environment in recent years. Therefore, more attention needs to be paid to programs targeting improvement in roadway design and driver behavior.

Effects of head restraint and seat redesign on neck injury risk in rear-end crashes.

Automobile insurance claims were examined to determine the rates of neck injuries in rear-end crashes for vehicles with and without redesigned head restraints, redesigned seats, or both. Results indicate that the improved geometric fit of head restraints observed in many newer vehicle models are reducing the risk of whiplash injury substantially among female drivers (about 37% in the Ford Taurus and Mercury Sable), but have very little effect among male drivers. New seat designs, such as active head restraints that move upward and closer to drivers' heads during a rear impact, give added benefit, producing about a 43% reduction in whiplash injury claims (55% reduction among female drivers). Estimated effects of Volvo's Whiplash Injury Prevention System and Toyota's Whiplash Injury Lessening design were based on smaller samples and were not statistically significant.

Rollover risk of cars and light trucks after accounting for driver and environmental factors.

Characteristics of the driver, roadway environment, and vehicle were associated with the likelihood of rollover occurrence in more than 14000 single-vehicle fatal and 78000 single-vehicle injury crashes during 1995-98. Rollovers were more likely in crashes involving young drivers or occurring on rural curves. After accounting for the effects of driver age and gender, roadway alignment and surface condition, and whether or not the crash occurred in a rural area, light trucks were still twice as likely as cars to experience rollovers. Some light truck models were much more likely than others to experience rollovers. However, while physical differences (e.g. center of gravity height) could explain some of this variability, other factors affecting vehicle stability may be evident only after dynamic testing.

Comparison of EuroSID-2 and SID-IIs in Vehicle Side Impact Tests with the IIHS Barrier.

The Insurance Institute for Highway Safety (IIHS) has recently developed and evaluated a new side impact barrier to represent the front profile of pickup trucks and sport utility vehicles for a new consumer information program. In the development of this program, two dummies were considered for assessing driver injury risk in side-struck vehicles: EuroSID-2 (50th percentile male dummy) and SID-IIs (5th percentile female dummy). The purpose of this study was to compare injury responses and kinematics for these two dummies in side impact crash tests. The findings suggest that SID-IIs will be more effective in driving relevant improvements in side impact crash protection.