Recent or noteworthy IIHS research is compiled here.
See our comprehensive bibliography for more on this or any other topic.
Comparison of BioRID injury criteria between dynamic sled tests and vehicle crash tests
Aylor, David A.; Zuby, David S.
Proceedings of the 22nd International Technical Conference on the. Enhanced Safety of Vehicles (CD ROM)
The Insurance Institute for Highway Safety rates vehicle
seat/head restraint designs as good, acceptable,
marginal, or poor using a protocol by the Research
Council for Automobile Repairs’ International Insurance
Whiplash Prevention Group (RCAR/ IIWPG).
Studies of insurance neck injury claim rates for rear
impact crashes show that vehicles with seats rated
good have lower claim rates than vehicles with seats
rated poor, but the relationship between acceptable/
marginal ratings and claim rates is less clear.
To better understand the relationship between measured
neck injury criteria and injury claim rates, a series of
rear impact crash tests was conducted to determine the
influence of crash pulse, as dictated by vehicle structure,
on the performance of seat/head restraints. The
role of head restraint adjustment also was examined by
comparing BioRID responses in the driver position,
with the restraint adjusted according to the RCAR/
IIWPG protocol, and in the front passenger position,
with the restraint adjusted to its lowest position. In an
attempt to match the severity of the RCAR/IIWPG
crash pulse, vehicles were struck by a flat rigid barrier
to create a velocity change of 16 km/h (10 mi/h).
Four small cars with rated seat/head restraints and
varying real-world neck injury claim rates were selected.
The 2006 Honda Civic and 2005 Chevrolet
Cobalt both received good ratings in the RCAR/
IIWPG sled test, but the Civic had a relatively low
neck injury claim rate compared with the Cobalt. The
2006 Saturn Ion and 2005 Ford Focus both received
marginal ratings in the sled test, but the neck injury
claim rate for the Ion was comparable with that for the
good-rated Civic, and the Focus had the highest neck
injury claim rate among the vehicles tested.
BioRID response ratings for the driver position
matched the sled test ratings for the Cobalt and Focus
but were one rating level lower for the Civic and Ion.
BioRID response ratings for the passenger position
were the same as those for the driver position for all
vehicles except the Cobalt, which was one rating level
lower. The findings suggest that changing the RCAR/
IIWPG protocol to include vehicle specific crash
pulses and/or changing the restraint setup would not
improve the relationship between seat/head restraint
ratings and neck injury claim rates. Furthermore,
examination of additional BioRID injury metrics not
currently assessed under the protocol does not help
explain real-world neck injury claim rates and does
not support changing the current evaluation criteria.
Additional research is needed to determine whether
vehicle underride/override alters vehicle accelerations
in a way that makes crash tests more predictive of
neck injury claim risk in rear-end collisions.
Seat design characteristics for whiplash mitigation as indicated by tests with BioRID
Zuby, David S.; Locke, Gerry; Aylor, David
Insurance Institute for Highway Safety
A series of simulated rear crashes conducted according to the seat/head restraint evaluation protocol of the Research Council for Automobile Repairs International Insurance Whiplash Prevention Group (RCAR/IIWPG) examined the effects on BioRID responses of changes in seatback configuration and rotation about the recliner pivot. In general, a more compliant seatback design that allowed the torso to sink-in as the seatback frame was accelerated forward was beneficial toward reducing forces measured in the dummy’s neck. The design of comfort features like lumbar supports influenced this seatback characteristic. Seatbacks that rotated less produced lower neck forces but higher T1 acceleration and NIC, suggesting a possible design conflict that might be resolved by attention to other seat design characteristics like seatback stiffness or initial backset. Comparison with earlier research by Locke et al. (2009) using the same set-up and seat back designs indicates the feasibility of seat/head restraint designs that satisfy the conditions for a good RCAR/IIWPG rating and the requirements of the Federal Motor Vehicle Safety Standard 202 dynamic compliance option.
Consumer whiplash ratings – Have they influenced seat designs in helpful ways?
Zuby, David S.; Lund, Adrian K.
FISITA 2010 World Automotive Congress Proceedings
This paper offers a historical review of vehicle design measures that have been implemented to reduce neck injury risk to occupants of rear-struck vehicles. In particular, the rationale behind ratings published by the Insurance Institute for Highway Safety (IIHS) is described. The paper also describes how seat and head restraint designs in US vehicles have changed during the 6 years IIHS has been rating passenger vehicle seats. Efforts to understand how well these ratings predict real crash injury risk are reviewed.
GLORIA: Design and development of a calibration jig for H-point machines used for the measurement of head restraint geometry
Avery, Matthew J.; Zuby, David S.; Gane, John W.; Cox, Mark Christopher
SAE Technical Paper Series 2008-01-0348
The SAE J826 H-point machine was designed to measure occupant accommodation dimensions relative to a loaded seat. It has become an intrinsic part of various crash dummy set up processes, but it has never had a formal calibration procedure. Whilst H-point location appears to be consistent from one device to another, the weight hanger locations show greater variability, and this can consequently affect the height and backset measurements of head restraints taken with a head restraint measuring device mounted upon the weight hangers. This paper describes the development of a calibration procedure and jig to measure the location of the weight hangers so that adjustments can be made if necessary. This procedure and calibration tool will enable more consistent seat evaluations, dummy set up, and consistently effective anti-whiplash seat designs.
Relationship of dynamic seat ratings to real-world neck injury rates
Farmer, Charles M.; Zuby, David S.; Wells, JoAnn K.; Hellinga, Laurie A.
Traffic Injury Prevention
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.
Relationship between seat rating test results and neck injury rates in rear crashes
Zuby, David S.; Farmer, Charles M.
Whiplash: Neck Pain in Car Crashes, 2nd International Conference Proceedings (CD-ROM)
Since 1969 motor vehicles in the United States have been required to have head restraints in front seats to mitigate neck injuries resulting from rear crashes. Simply equipping cars with head restraints reduced the incidence of these injuries by as much as 18 percent (Kahane, 1982; O’Neill et al., 1972; States and Balcerak, 1973). Further injury reductions were realized as head restraint designs evolved to be taller and closer to the backs of occupants’ heads in response to seat ratings published by the Insurance Institute for Highway Safety (IIHS) and other members of the Research Council for Automobile Repairs (RCAR) (Chapline et al., 2000; Farmer et al., 1999; Farmer et al., 2003). Led by Saab and Volvo in the 1990s, vehicle manufacturers began fitting more advanced seat designs specifically to address whiplash in rear crashes. These also were shown to be effective at reducing neck injury risk (Farmer et al., 2003; Jakobsson and Norin, 2004; Viano and Olson, 2001). Despite these improvements whiplash, or minor injury to the neck, is one of the most common consequences of motor vehicle crashes, affecting nearly 1 million people annually in the United States. Many of these injuries still occur in rear crashes (National Highway Traffic Safety Administration, 2004).
Improved seat and head restraint evaluations
Edwards, Marcy; Smith, Sarah; Zuby, David S.; Lund, Adrian K.
Proceedings of the 19th International Technical Conference on the Enhanced Safety of Vehicles (CD-ROM)
Since 1995 the Insurance Institute for Highway Safety (IIHS) has measured and evaluated the static geometry of head restraints on vehicle seats. Geometry is important because a restraint positioned behind and close to the back of an occupant’s head is a necessary first step toward reducing neck injury risk in rear crashes. In recent years head restraint geometry in new model passenger vehicles has improved steadily. However, a restraint that does not remain close to the head during a crash cannot effectively support the head and neck, so the effectiveness of a restraint with good static geometry may be reduced by poor dynamic response of a seatback or restraint cushion. In addition, the effectiveness of advanced seat and head restraints designed to move during a crash, either to improve geometry or reduce torso accelerations, can be evaluated only in dynamic tests. Thus, good geometry is necessary but, by itself, not sufficient for optimum protection. Dynamic evaluations using a test dummy also are needed to assess protection against neck injury in rear crashes. Several insurance-sponsored organizations formed the International Insurance Whiplash Prevention Group to develop a seat/head restraint evaluation protocol, including a dynamic test. Tests using this protocol produce substantially different results among seat/head restraint combinations, even among those with active head restraints. IIHS published its first set of evaluations using the protocol in fall 2004. This paper describes the rationale behind the protocol and summarizes the results of IIHS testing so far.
Effects of head restraint and seat redesign on neck injury risk in rear-end crashes
Farmer, Charles M.; Wells, JoAnn K.; Lund, Adrian K.
Traffic Injury Prevention
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.
The influence of crash pulse shape on BioRID response
Zuby, David S.; Farmer, Charles M.; Avery, Matthew
Proceedings of the 2003 International IRCOBI Conference on the Biomechanics of Impact
The magnitude of crash acceleration affects neck injury risk in rear crashes. It is less clear whether different shaped crash pulses of similar overall severity also cause different injury outcomes. This study examined two crash pulse shape characteristics and their effects on dummy responses in rear crashes: 1) oscillations of approximately twice the frequency of the main mode typical of full-scale crash tests and 2) timing of the maximum peak acceleration. The presence of acceleration oscillations did not influence the magnitudes of BioRID responses. The timing of peak sled acceleration did affect both the timing and magnitude of some BioRID responses.
BioRID responses and the effect of crash pulse characteristics
Zuby, David S.; Avery, Matthew
IMechE Conference Transactions: International Conference on Vehicle Safety 2002
Comparisons of whiplash injury risk among different vehicle seat/head restraint designs using dynamic tests requires consideration of rear-crash-pulse characteristics in a range of low to moderate crash severities. Insurance damageability tests show that for many European cars the rear structures are becoming stiffer and tend to produce crash pulses with higher peak accelerations occurring earlier than was observed with older designs. In addition, many modern vehicles have a distinctly bimodal rear-end crash pulse. The influence of these pulse-shape characteristics on neck injury risk is unknown. In this study, 21 sled tests were conducted with new current-model car seats supplied by three different vehicle manufacturers. Each seat was subjected to one of seven different rear crash pulses that varied in maximum acceleration (7.1-9.5 g), delta V (16-20 km/h), and shape (unimodal versus bimodal with different acceleration rates). One of the bimodal pulses was an average of pulses recorded in a number of approximately 16 km/h delta V car-to-car crash tests. One of the unimodal pulses approximates the trapezoidal shape proposed by the International Insurance Whiplash Prevention Group. BioRID neck responses measured in these tests included NIC, Nkm, Nij, and NDC. Analyses show that higher accelerations produced consistently higher NIC, Nij, and Nkm responses, but the other injury measures did not exhibit the same pattern. Nij and Nkm also increased with delta V, but other injury measures did not. The effects of pulse shape for all injury measures were unclear. Although all of the injury measures varied as the test-pulse shape was changed, only some injury measures exhibited consistency across the different seat models tested, so it is not possible to know whether the variation in injury measures was due to test pulse differences or only reflected underlying test-to-test variability.
Comparison of driver head positions -- volunteers versus dummies
Edwards, Marcy A.; Zuby, David S.; Nelson, Laurie A.
Proceedings of the 2002 International IRCOBI Conference on the Biomechanics of Impact
This paper describes a test to assess the postural comparability between the anthropometric dummy BioRID II, the head restraint measuring device HRMD, and humans of similar size. Volunteers were monitored while driving vehicles along a course which involved certain movements. Measurements were made of each volunteer's head relative to the head restraint. The driver's seat position and angles were also measured. It was found that seat back angles were more upright than those used for a dummy but the difference was not great. Seat adjustment meant that the dummy tended to sit lower in the seat than the human, making a difference to the position of the head restraint relative to the head. The study concluded that the seating positions of BioRID and HRMD were appropriate.
Neck pain and head restraint position relative to the driver's head in rear-end collisions
Chapline, Janella F.; Ferguson, Susan A.; Lillis, Robert P.; Lund, Adrian K.; Williams, Allan F.
Accident Analysis and Prevention Special Issue: Whiplash
This two-year investigation was designed to estimate the incidence of driver neck pain in rear-struck vehicles involved in two-vehicle collisions and to determine the relationship between neck pain and specific vehicle, human, and environmental factors. Neck pain percentages were significantly higher for female (45%) than for male (28%) drivers. For female and male drivers, neck pain likelihood increased as head restraint height decreased below the head's center of gravity, although this effect was significant only for females. Head restraint backset, the horizontal distance measured from the back of the driver's head to the front of the head restraint, was not found to be related to neck pain for female drivers. Backset trends for male drivers could not be evaluated because few male drivers had head restraints that were high enough for backset to be relevant. Reported neck pain decreased for older drivers (females only), drivers in less severe crashes, and drivers in heavier cars (females only); all head restraint analyses were adjusted for these characteristics. Women, and most likely men, in the United States would benefit greatly from international harmonization to European head restraint standards. Until then, both women and men should be encouraged to adjust their adjustable head restraints, if possible, behind their heads' centers of gravity and to sit with the backs of their heads as close as possible to their head restraints.
Relationship of head restraint positioning to driver neck injury in rear-end crashes
Farmer, Charles M.; Wells, JoAnn K.; Werner, John V.
Accident Analysis and Prevention
Insurance claims were examined for evidence of neck injuries to drivers of passenger cars struck in the rear. Neck injury rates were significantly lower for male drivers, elderly drivers, and drivers in less severe crashes. Even after accounting for differences in driver demographics and crash severity, neck injury rates were significantly lower for drivers of cars with head restraints that were more likely to be behind the heads of motorists.