ArticlePDF Available

Abstract and Figures

Motor vehicle collisions are the leading cause of trauma-related death in the United States. Reclined seatbacks may alter crash kinetics and affect occupant outcome. We examined the effect of reclined seatbacks on occupant mortality. Our study population consisted of United States traffic crashes from 1995 to 2005, using data from the Crash Injury Research and Engineering Network and the National Automotive Sampling System Crashworthiness Data System. Phase 1, we performed a detailed review of crash kinetics and biomechanical factors resulting in injury patterns in fully reclined occupants. Phase 2, we performed a population-based retrospective cohort study comparing outcome in upright, partial, and full recline positions. Primary outcome measure was 30-day mortality. Phase 1, flexion and compression injuries over pretensioned lap and shoulder belts resulted in severe thoracoabdominal and spine injuries in restrained occupants, with a high associated mortality. Increased lower extremity injuries from additional force loads into bolsters and panels were also noted. Phase 2, the majority (>50%) of front-seat occupants was partially reclined. Fully reclined occupants were younger (30 vs. 39 years, p < 0.0001), more likely to be male (70% vs. 49%, p < 0.0001) and less likely to wear a seat belt (58% vs. 78%, p < 0.0001) than upright or partially reclined occupants. Mortality was increased in both partially (adjusted odds ratio 1.15, 95% confidence interval 1.05-1.26) and fully reclined occupants (adjusted odds ratio 1.77, 95% confidence interval 1.09-2.88). The reclined position is associated with increased occupant mortality in motor vehicle collisions.
Content may be subject to copyright.
The Effect of Reclined Seats on Mortality in Motor
Vehicle Collisions
Sharmila Dissanaike, MD, Robert Kaufman, BS, Christopher D. Mack, MS, Charles Mock, MD, MPH,
and Eileen Bulger, MD
Background:
Motor vehicle collisions
are the leading cause of trauma-related
death in the United States. Reclined seat-
backs may alter crash kinetics and affect
occupant outcome. We examined the effect
of reclined seatbacks on occupant mortality.
Methods:
Our study population con-
sisted of United States traffic crashes from
1995 to 2005, using data from the Crash
Injury Research and Engineering Network
and the National Automotive Sampling
System Crashworthiness Data System.
Phase 1, we performed a detailed review
of crash kinetics and biomechanical fac-
tors resulting in injury patterns in fully
reclined occupants. Phase 2, we performed a
population-based retrospective cohort study
comparing outcome in upright, partial, and
full recline positions. Primary outcome mea-
sure was 30-day mortality.
Results:
Phase 1, flexion and com-
pression injuries over pretensioned lap
and shoulder belts resulted in severe tho-
racoabdominal and spine injuries in re-
strained occupants, with a high associated
mortality. Increased lower extremity inju-
ries from additional force loads into bol-
sters and panels were also noted. Phase 2,
the majority (>50%) of front-seat occu-
pants was partially reclined. Fully re-
clined occupants were younger (30 vs. 39
years, p<0.0001), more likely to be male
(70% vs. 49%, p<0.0001) and less likely
to wear a seat belt (58% vs. 78%, p<
0.0001) than upright or partially reclined
occupants. Mortality was increased in both
partially (adjusted odds ratio 1.15, 95%
confidence interval 1.05–1.26) and fully
reclined occupants (adjusted odds ratio
1.77, 95% confidence interval 1.09 –2.88).
Conclusion:
The reclined position is
associated with increased occupant mor-
tality in motor vehicle collisions.
Key Words:
Motor vehicle collision,
CIREN, NASS, Reclined seatback.
J Trauma. 2008;64:614 – 619.
Motor vehicle collisions (MVC) remain the leading
cause of trauma-related death, and the third overall
cause of death in the United States. Many factors
impact the severity of injury and mortality in MVCs. These
include collision factors such as the change in velocity (V),
primary direction of force (PDOF), and type of vehicles
involved
1–3
as well as occupant factors such as height and
weight.
4,5
Seat belt use and airbag deployment have improved
outcomes in recent decades, although restraint systems them-
selves have been associated with specific injury patterns.
6–9
Vehicle crash testing is designed to evaluate the safety of
vehicle design and assess the impact of various factors on
MVC-related injury and death. Tests are routinely performed
in the United States by the National Highway Traffic Safety
Administration’s New Car Assessment Program and the In-
surance Institute for Highway Safety (IIHS). The tests are
performed with the crash test dummy in the upright (UP)
position, as recommended by the vehicle manufacturers as
the optimal driving position.
10,11
However, many crash vic-
tims (and motorists in general) have their seats partially (PR)
or fully reclined (FR). Passengers may fully recline their seats
while sleeping, especially on long trips. The practice of driv-
ing with the seatback reclined, the seat in rear track position
and left arm extended forward on the steering wheel can be
seen on many popular music videos and on the streets.
There have not been any studies to date investigating the
effect of reclined seatbacks on MVC outcome. We sought to
evaluate the impact of FR and PR reclined seat back positions
on injury patterns and mortality in MVC. We hypothesized
that specific injury patterns may be identified after frontal
collisions with occupants in the reclined position, and that
this may lead to increased mortality.
MATERIALS AND METHODS
This study consisted of two phases. In phase 1 we re-
viewed cases from the Crash Injury Research and Engineer-
Submitted for publication August 30, 2007.
Accepted for publication December 10, 2007.
Copyright © 2008 by Lippincott Williams & Wilkins
From the Division of Trauma/Critical Care Surgery, Harborview Med-
ical Center (S.D., E.B.), Harborview Injury Prevention and Research Center
(R.K., C.D.M., C.M.).
Supported by NHTSA under Cooperative Agreement Number
DTNH22-05-H-11001.
Work was performed for the Crash Injury Research and Engineering
network (CIREN) project at the University of Washington/Harborview In-
jury Prevention and Research Center in cooperation with the US Department
of Transportation/National Highway Traffic Safety Administration (USDOT/
NHTSA).
Views expressed are those of the authors and do not represent the views
of NHTSA. Study design, data acquisition, analysis and interpretation, manu-
script preparation, and review were conducted independent of sponsoring
organization. The final version of this manuscript has been submitted for
review to NHTSA.
Presented as a poster at the 66th Annual Meeting of the American
Association for the Surgery of Trauma, September 27–29, 2007, Las Vegas,
Nevada.
Winner of the Region X American College of Surgeons 2007 Resident
Trauma Paper Competition.
Address for reprints: Sharmila Dissanaike, MD, Department of Sur-
gery, Texas Tech University Health Sciences Center, 3601 4th St., Mailstop
8312, Lubbock TX 79430; email: sharmila.dissanaike@ttuhsc.edu.
DOI: 10.1097/TA.0b013e318164d071
The Journal of TRAUMAInjury, Infection, and Critical Care
614 March 2008
ing Network (CIREN) database, to identify specific injury
patterns associated with reclined occupants. This database
contains detailed information of the biomechanical factors
involved in the collisions, including reconstruction of the
sequence of events leading to the particular injury patterns
sustained.
In phase 2 we utilized the National Automotive Sam-
pling System (NASS) subset Crashworthiness Data System
(CDS) to evaluate the population-based impact of seatback
position and the relationship to outcome after MVC.
The University of Washington Institutional Review
Board for human subject research approved this project.
Phase 1
We performed an in-depth review of cases with reclined
occupants using the Crash Injury Research Engineering Net-
work database (CIREN). The Harborview Injury Prevention
and Research Center is one of eight centers contributing to
this resource. The database (1996 –present) consist of detailed
case reviews of serious MVCs, establishing patterns of injury
and correlating clinical findings with crash scene kinetics.
Each case contains approximately 650 crash elements and
250 medical elements for each occupant. The crash investi-
gator records details of the crash (e.g., skid marks, scaled
drawing of impact locations) that are used to reconstruct the
mechanics of the collision. The vehicles are inspected to
assess the damage severity, interior intrusion, restraint use,
and occupant contact marks. Prehospital data are obtained
from emergency medical services records. Structured inter-
views are conducted with each occupant, and precrash seat
position is specifically queried. Patient observation teams at
the trauma center record details of the patient’s hospital
course, radiologic findings, operations, and outcome. The
crash investigator, bioengineers, physicians including a
trauma surgeon and radiologist, and a research nurse review
each case and establish mechanism of injury based on clinical
and crash investigation findings.
We queried the database for cases involving front seat
occupants found in the FR position to elucidate the mecha-
nisms involved. We focused on analysis of the occupant
kinematics by evaluating the restraint systems, and specific
contact evidence such as skin transfers, hair and blood pat-
terns, scuff marks, and deformity found on the interior com-
ponents. These injury patterns were then correlated with the
patient’s clinical and radiologic findings.
Phase 2
We analyzed outcomes of occupants in upright, PR and
FR positions using a large national database, the NASS subset
CDS. The NASS/CDS project is sponsored by the National
Highway Traffic Safety Administration, and is a probability
sample of all police-reported tow-away MVCs that result in
injury, death, or property damage each year in the United
States. A crash investigation and detailed interviews are per-
formed, similar to that described for CIREN. The variable
“recline position” is assessed based on the crash investigator’s
vehicle inspection, and supported by occupant interviews.
The NASS/CDS guidelines categorize recline as upright (per-
pendicular to the seat cushion), full (reclined to the maximum
rearward position), and slight (partial) recline.
12
All injuries
are documented and scored using the Abbreviated Injury
Severity (AIS) 90 coding. Data on approximately 5,000
MVCs are collected annually. This data are then weighted to
provide a national estimate. Data on recline position has only
been available in NASS/CDS since 1995. We selected all
cases with adjustable seatbacks between 1995 and 2005 for
inclusion in our study.
Analysis was restricted to front seat occupants in the
driver or passenger position. Patient characteristics recorded
include patient age, sex, height, and weight. Details regarding
vehicle type, principal direction of force (PDOF), rollovers,
ejection from vehicle, and total vehicle velocity change dur-
ing impact (V) were collected. Extent of seatback recline,
seat-track position, and seat belt use were noted for each
occupant. The Injury Severity Score was used to quantify
injury severity. AIS scores for the head, thorax, abdomen, and
lower extremity were also analyzed to determine whether any
specific region accounted for an increase in injury or mortal-
ity. Mortality was defined as occupant death within 30 days
of MVC.
Statistical Analysis
Initial analysis consisted of paired ttests and
2
tests
comparing variables in PR and FR with the UP position. An
analysis of variance (ANOVA) was then performed to com-
pare means of the three recline positions with Tukey-Kramer
tests of significance. Univariate and multivariate logistic regres-
sions were performed to estimate unadjusted and adjusted
effects on outcome. Confounders including age, sex, height
and weight, seat belt use, and crash kinetics were incorpo-
rated into the multivariate analysis. The interaction between
seat belt use and recline status was tested and found to be
insignificant. Data were also analyzed using a 1:3 case-
control conditional logistic regression model, which pro-
duced results consistent with our findings. Significance was
set at p0.05, and 95% confidence intervals (CI) were
used for odds ratio (OR) estimation. Analysis was per-
formed using SAS Base and SAS/Stat software (SAS In-
stitute Inc., Cary, NC).
RESULTS
Phase 1. CIREN
There were 11 cases of FR occupants in the complete
CIREN database. A brief summary is shown in Table 1. Detailed
review of the eight frontal impact cases revealed two character-
istic injury patterns that appear to be associated with the reclined
position. Two illustrative cases are described below.
Effect of Reclined Seat on Mortality in MVC
Volume 64 Number 3 615
Case 1
The case occupant was a 65-year-old woman, (170 cm/
136 kg) who was the front seat restrained passenger of a 2006
Scion TC two-door hatchback. The driver approached a line
of stopped vehicles at 89 kmph/55 mph on a two-lane high-
way, and swerved right, departing the roadway and sustaining
a frontal impact into a large tree. The estimated V was 48
kmph/30 mph. The case occupant was wearing her manual
lap and shoulder belt and had been asleep with her seatback
FR at the time of impact. Driver and passenger airbags
deployed and the seat belt pretensioner actuated upon impact.
The reclined occupant suffered several major injuries,
which resulted in her death at the scene. Based on findings at
the crash scene, examination of the vehicle interior, clinical
and radiologic findings, the final reconstruction of the series
of events at the time of the collision is as follows: the
occupant was lying in the FR position, with her chest several
centimeters away from the shoulder belt. Pretensioners in the
seat belt system fired automatically upon impact, resulting in
the seat belt webbing being pulled taut instantly. Upon im-
pact, the occupant initiated a forward response to the 12
o’clock principal direction of force and loaded the shoulder
belt with her torso. This resulted in a lateral contusion across
her upper chest from the seat belt webbing, and associated
smudge marks on the belt. The resulting thoracic injuries
included fractures of ribs 6 to 10 on the right and 2 to 8 on the
left. The shoulder belt is designed to fit snugly in the upright
position, lying more vertically against the chest, to prevent
flexion and compression injuries of this nature. Her injuries
were attributed to the abnormal body position relative to the
seat belt.
Head movement during the rapid deceleration force re-
sulted in lethal shear injuries to her brain, an atlanto-occipital
fracture, diffuse subarachnoid hemorrhage, and lacerations to
the brain stem. In the upright position, her head would have
interacted with the airbag deployment and potentially reduced
the injury severity.
The lap belt was positioned across her upper abdomen
rather than her pelvis while she was reclined, and this resulted
in an abrasion over the upper abdomen with multiple associ-
ated mesenteric lacerations. She also sustained a posterior
pelvic fracture involving the left sacroiliac joint. During the
collision her lower extremities impacted the glove compart-
ment, instrument panel, and floor pan resulting in contusions
and lacerations to both legs.
The majority of the occupant’s injuries appear to be a
result of being flung forward while in a FR position against
the already taut safety belt, causing direct injury to the chest
and abdomen as well as a deceleration injury to the head and
spine. A similar injury pattern was seen in two other cases
involving restrained passengers in a FR position, including
one other fatality.
Case 2
The case occupant was a 17-year-old male driver of a
2003 Honda civic two-door coupe. His seat was FR with no
safety belts utilized. He sustained a head-on frontal collision
with a compact sport utility vehicle. The estimated V was
40 kmph/25 mph. Upon impact, the unbelted occupant moved
forward while remaining in the FR position and slid under the
steering rim, which was deformed inferiorly. Abrasions on
his chest confirmed this pattern of injury, although he did not
sustain severe chest or abdominal trauma. As he moved
forward his legs contacted the front bolster system. The left
knee completely deformed the left bolster plate, whereas the
right knee struck the edge of the right bolster plate.
The bolster system has two key safety functions. It is
designed to absorb force through the lower extremities as
well as maintain the upright occupant posture, to facilitate
airbag deployment and function. The FR position resulted in
an increased force load through the bolsters that led to several
lower extremity injuries, including a fracture of the posterior
left acetabulum and open left femur fracture, an open intra-
articular fracture of the right knee and tibial plateau with
associated large laceration and soft-tissue avulsion. The oc-
cupant’s left arm had been outstretched with hand positioned
on top of the steering rim. His hand cracked the windshield
resulting in a small fracture and laceration.
The serious lower extremity fractures with minimal other
injuries suggest a frontal impact injury pattern with the legs
taking much of the load in the FR position.
Phase 2. NASS/CDS
Occupant and Collision Characteristics
There were a total of 90,412 cases recorded in the data-
base between 1995 and 2005. There were 15,938 UP (17.6%),
45,250 PR (50%), and 280 FR (0.3%) front-seat occupants
recorded during the 11-year period. Data on recline position
was incomplete for 21,771 (24%) occupants and the seat was
not adjustable for 7,173 (8%) occupants. Analysis of the
incomplete group revealed that their demographic and out-
come variables were very similar to the upright and PR
reclined occupants, suggesting that their exclusion would not
bias our findings.
Occupant characteristics are shown in Table 2. FR oc-
cupants were significantly more likely to be young and male.
Table 1 Details of Reclined Front-Seat MVC
Occupants in CIREN Database
Age (range) 32.4 yr (16–75)
Male (%) 6 (54.5)
Case occupant was front passenger (%) 8 (72.7)
Height, weight (range) 172.1 cm (150–185),
85.3 kg (57–122)
V (range) 47.4 kmph (24–68)
12 o’clock/frontal impact (%) 8 (72.7)
Airbag deployed (%) 6 (54.5)
Seatbelt used (%) 6 (54.5)
Mean Injury Severity Score (range) 27.8 (2–75)
Mortality (%) 3 (27.3)
The Journal of TRAUMAInjury, Infection, and Critical Care
616 March 2008
The driver-to-passenger ratio was lower in FR compared with
UP and PR. Occupants who FR their seat backs were more
likely to place their seats in midrear and rear track position
(p0.025). There was a significantly lower rate of seat belt
use in FR (57.8%) compared with UP (77.9%) ( p0.0001).
PR had a similar frequency of seat belt use (75.6%) as UP
occupants (Fig. 1).
There were no differences in V, PDOF, ejection, or
rollover collisions, indicating similar mechanisms and force
of impact across groups.
Injury Severity
Overall injury severity was increased in FR occupants,
with a mean Injury Severity Score of 7.2 compared with 5.5
in PR, and 5.7 in UP ( p0.0428). There was no clear pattern
of increased severity in any particular body region, with FR
showing a trend toward increased severity in most AIS cat-
egories (head, thorax, abdomen, spine, and lower extremity)
that was not statistically significant (Table 3).
Mortality
Mortality was significantly increased in FR at 7.5%,
compared with 4.4% in UP ( p0.0049). A smaller increase
in mortality to 4.9% was seen in PR (Fig. 2). After correction
for seat belt use, age, sex, and collision factors, mortality
remained significantly increased in FR, with an adjusted OR
of 1.77 (95% CI 1.09 –2.88). There was also a significant
increase in mortality for PR, with an adjusted OR of 1.15
(95% CI 1.05–1.26) (Table 4). Multivariate analysis using a
1:3 case-to-control conditional logistic regression model con-
firmed the significant increases in mortality with PR and FR.
In light of the CIREN findings showing flexion over the
seat belt as a potential injury mechanism, we reanalyzed the
data using a logistic regression model with interaction terms
to elucidate a potential interaction between seatbelts and
recline position. We did not find a significant interaction for
either FR ( p0.87) or slightly reclined ( p0.93) occu-
pants, and seat belt use was protective for all three categories.
DISCUSSION
Several key findings were noted in our study. The ma-
jority of the population, both drivers and passengers, appear
to favor a partial recline, which likely represents the most
comfortable traveling position. A very small proportion trav-
els with a FR seatback. The FR were predominantly young
men, and were less likely to use a seat belt. Several studies
have shown a lower incidence of seat belt use in the young
male population, which is likely symptomatic of a higher
incidence of risk-taking behavior in general.
13–15
There are several reasons why occupants may place their
seatbacks in full recline. There were a significantly greater
proportion of passengers versus drivers in the FR group
compared with UP and PR, and it is likely that many of these
passengers pushed their seats back to a greater degree to sleep
while traveling. We were initially surprised to find that nearly
50% of occupants in the FR position were drivers. FR occu-
Occupants wearing seatbelts
0
20
40
60
80
100
UP PR F R
Sea tback position
Percentage
Belted
Unbelted
Fig. 1. Rates of seat belt use as a percentage of the population in
upright (UP), partial (PR), and full recline (FR).
Mortality
0
1
2
3
4
5
6
7
8
UP PR FR
Seatback position
Percentage
Mortality
Fig. 2. Unadjusted mortality rate as a percentage of the population
in upright (UP), partial (PR), and full recline (FR).
Table 2 Characteristics of Front-Seat Occupants in
NASS/CDS Database
UP
(n 15,938)
PR
(n 45,520)
FR
(n 280) P
Mean age (yrs) 39.4 35.7 29.6 0.0001
Male sex (%) 49 55 70 0.0001
Mean height (cm) 170.1 171.4 174 0.0001
Mean weight (kg) 75.9 75.8 79 0.0497
Driver (%) 80 78 48 0.0001
Table 3 Injury Severity Score According to Recline
Position in NASS/CDS Patients
Injury Severity Score UP PR FR
Mean ISS (SD) 5.7 (14) 5.5 (14) 7.2 (16)
0 17% 17% 28%
1–8 52% 52% 40%
9–25 20% 20% 19%
2511% 11% 13%
Table 4 Mortality Risk With Full or Partial Recline,
Compared With Occupants in the Upright Position
Seat Position Adjusted Odds Ratio
for Mortality 95% CI
Partial reclined 1.15 1.05–1.26
Fully reclined 1.77 1.09–2.88
Adjusted for age, sex, height, weight, seatbelt use.
Effect of Reclined Seat on Mortality in MVC
Volume 64 Number 3 617
pants were slightly taller, possibly associated with the in-
creased proportion of men in this group. Although this in-
crease in height may have contributed to their choice of FR
(and ability to drive while in this position), it is unlikely to be
the sole explanation. Further investigation revealed that the
combination of extended arms and legs, with seat reclined
back as far as feasible to afford a view of the road, reflects a
style of driving popular among young urban men in particu-
lar. Combined with a tilt toward the passenger side of the car
with right elbow resting on the center armrest, this position is
described as the “Gangsta lean”.
16
Several mechanisms may be responsible for the in-
creased mortality in the reclined position. We were able to
identify two characteristic injury patterns in FR from our
CIREN analysis. Despite some suggestion that the seat belt
may itself be a contributory factor in injuries sustained in the
reclined belted position, we could not confirm this finding in
the NASS/CDS analysis. It is likely that there are many other
features of crash kinetics that come into play with frontal
impact from a reclined position. As we collect more cases
into the CIREN database we will continue to elucidate the
other injury mechanisms and factors responsible. The average
injury severity in the CIREN database is higher than in
NASS/CDS (28 vs. 6), which reflects the selection of more
severely injured cases into the former database. The mecha-
nisms we identified may not be a factor in the majority of less
severely injured occupants, and thus not reflected in the
larger population-based analysis.
Although the increase in odds of mortality (OR 1.77) was
greatest in FR occupants, the smaller increase (OR 1.15) in
PR reclined occupants affects a much larger population, and
represents a significant public health concern. Performing
crash testing in the reclined position would be an invaluable
tool in identifying the precise mechanism of injury that results in
a worse outcome, and possible vehicle design improvements
that may minimize this risk. One possible intervention may
be the utilization of integrated seatbelts. These are designed
with the shoulder belt attachments to the top of the seatback
itself, rather than the B pillar, and thus, the belt remains in
close apposition to the body regardless of seatback position.
Several newer vehicle models already incorporate this fea-
ture. Although there is no evidence that this relatively new
technology will reduce mortality, the crash kinetics noted in
several of our CIREN cases suggest that an improved pro-
tective effect is mechanistically plausible.
17
Manufacturing vehicles without the capacity for front
seat recline would be a simple and effective method to elim-
inate this additional risk. However, it is unlikely that this
protective measure will be welcomed by the consumer. In
similar vein, public education regarding the risks of reclined
seats while traveling may not have much effect on the FR
population, who are already prone to ignoring the well-estab-
lished risk of traveling without a seat belt. However, people
who place their seats in partial recline represent the majority
of motor vehicle occupants, who are likely unaware of the
potential risks of this position. Education regarding the in-
crease in mortality with reclined seats may have a role in
reducing the public health impact of MVC nationwide.
Our study has several limitations. Most importantly, we
are reliant on the accuracy of information of two separate
databases. Errors in documentation of seatback position
would affect the validity of our findings. The categorization
as upright, partial, or full recline is based on the crash inves-
tigator assessment. The current guidelines do not quantify
seatback angles for each category, and investigators may not
have coded seatback position in a uniform manner. This lack
of exact measurement would tend toward a nondifferential
misclassification, because we have no evidence to suggest
that investigators would preferentially select one category
over the other. This would result in a lowering of the statis-
tical power to detect a difference between groups, and our
findings may be an underestimate of the true effect of seat
position.
Lack of accurate data are the likely explanation for the
high number of occupants in NASS/CDS—nearly a quarter of
the population—that did not have seatback position recorded
in the database. Seatback position may change during the
extrication process, and despite efforts of obtain information
from emergency service personnel and occupants, it may not
always be possible to determine the recline status. The de-
mographic and outcome variables of the group with missing
data were similar to the upright and PR reclined occupants
included in our analysis. Nevertheless, it is possible that
reclined occupants were disproportionately represented in
this group and their omission may have affected our findings.
Finally, the comparatively low numbers of occupants in the
FR position in NASS/CDS precluded any meaningful sub-
group analysis.
We have attempted to compare our results with the
established literature on seat position and MVC. We per-
formed a search using the Pubmed database, with search
terms “seat position”, “seatback”, “recline”, “occupant char-
acteristic”, and “crash characteristics”, individually and in
conjunction with the term “motor vehicle collision”. How-
ever, we were unable to find any studies on this issue, and
think this is the first published analysis of the effect of
seatback position on MVC outcome.
In conclusion, both FR and PR reclined seats appear to
be an independent risk factor for mortality in MVCs.
REFERENCES
1. Acierno S, Kaufman R, Rivara FP, et al. Vehicle mismatch, injury
patterns and severity. Accid Anal Prev. 2004;36:761–772.
2. Seigel JH, Smith JA, Siddiqi SQ. Change in velocity and energy
dissipation on impact in motor vehicle crashes as a function of the
direction of the crash. J Trauma. 2004;57:760 –777.
3. Newgard CD, Lewis RJ, Kraus JF, et al. Seat position and the risk
of serious thoracoabdominal injury in lateral motor vehicle crashes.
Accid Anal Prev. 2005;37:668 – 674.
4. Chong M, Sochor M, Ipaktchi K, et al. The impact of occupant
factors on the lower extremity fractures in frontal collision of motor
The Journal of TRAUMAInjury, Infection, and Critical Care
618 March 2008
vehicle crashes based on a Level I trauma center. J Trauma. 2007;
62:720 –729.
5. Mock CN, Grossman DC, Kaufman RP, et al. The relationship
between body weight and risk of death and serious injury in motor
vehicle crashes. Accid Anal Prev. 2002;34:221–228.
6. Crandall CS, Olson LM, Sklar DP. Mortality reduction with airbag
and seatbelt use in head-on passenger car collisions. Am J
Epidemiol. 2001;153:219 –224.
7. Rivara FP, Koepsell TD, Grossman DC, et al. Effectiveness of
automatic shoulder belt systems in motor vehicle crashes. JAMA.
2000;283:2826 –2828.
8. Stewart TC, Girotti MJ, Nikore V, et al. Effect of airbag deployment
on head injuries in severe passenger motor vehicle crashes in
Ontario, Canada. J Trauma. 2003;54:266 –272.
9. Francis DO, Kaufman R, Yueh B, et al. Airbag induced orbital
blow-out fractures. Laryngoscope. 2006;116:1966 –1972.
10. Insurance Institute for Highway Safety. Guidelines for Using the
UMTRI and ATD Positioning Procedure for ATD and Seat
Positioning (Version V). 2004. Available at: www.iihs.org.
11. 49 Code of Federal Regulations (CFR) Chap V. Section 8.1.3
p569 —New Car Assessment Program, National Highway Traffic
Safety Administration. Available at: http://www.gpoaccess.gov/cfr/
index.html.
12. National Accident Sampling System, Crashworthiness Data System.
Editing and Coding Manual. National Highway Traffic Safety
Administration, Department of Transportation; 2006.
13. Lerner EB, Jehle DV, Billittier AJ, et al. The influence of
demographic factors on seatbelt use by adults injured in motor
vehicle crashes. Accid Anal Prev. 2001;33:659 – 662.
14. Allen S, Zhu S, Sauter C, et al. A comprehensive state-wide analysis
of seatbelt non-use with injury and hospital admissions: new data,
old problem. Acad Emerg Med. 2006;13:427–434.
15. Liang W, Shediac-Rizkallah MC, Celentano DD, et al. A population
based study of age and gender differences in patterns of health
related behaviors. Am J Prev Med. 1999;17:8 –17.
16. “Gangsta Lean”. Available at: www.urbandictionary.com,
www.rapdict.org.
17. Rashidi M, Deshpande B, Gunesekar TJ, et al. Analytical Evaluation of
an Advanced Integrated Safety Seat Design in Frontal, Rear, Side and
Rollover Crashes. National Highway Traffic Safety Administration.
Paper No. 305. 2006. Available at: www.nrd.nhtsa.dot.gov/pdf/nrd-11/
17ESV_351.pdf.
Effect of Reclined Seat on Mortality in MVC
Volume 64 Number 3 619
... Current restraints are designed for upright seated occupants and they may not prevent injury to partially or fully reclined occupants. A previous study has evaluated the effect of reclined seats on mortality in motor vehicle crashes between 1995 and 2000 using data from the Crash Injury Research and Engineering Network (CIREN) and the National Automotive Sampling System Crashworthiness Data System (NASS CDS) (Dissanaike et al. 2008). Only a few cases were available to review within CIREN, and it was found that fully and partially reclined passengers demonstrated more severe head, thoracic, abdominal, spinal and lower extremity injury ranging from AIS 2-6 compared to upright occupants. ...
... Head injuries were suspected to be the results of the lack of interaction with the deployed airbag. The more severe chest injuries were interpreted as the result of the lack of the contact between shoulder seatbelt and chest at the impact (Dissanaike et al. 2008). Therefore, additional research is needed to understand restraint modifications for future reclined passengers which may reduce the injury risk. ...
Article
Objective: The effect of reclined seatbacks during frontal crashes in children seated on a belt-positioning booster (BPB) is not understood. Therefore, the aim of this study is to examine submarining in reclined child occupants with and without a BPB and with and without a simulated pre-pretensioner (PPT). We used the Large Omnidirectional Child (LODC) Anthropomorphic Test Device (ATD) seated on a production vehicle seat with and without a moderately reclined seatback angle during sled-simulated frontal vehicle crashes. Methods: Ten sled-simulated frontal impact tests were performed (24 g peak, 80 ms duration, 56 km/h delta-V). An adjustable D-ring anchor simulated a seat integrated belt. A fixed load-limited 3-point seatbelt webbing system was used to secure the LODC to a vehicle seat and booster seat. We compared the following conditions: a) BPB vs no-BPB and b) 25° versus 45° seatback angles, c) PPT, vs no-PPT in 45° seatback condition, each test was repeated. Abdominal forces (left and right), seatbelt loads, Anterior-Superior-Illiac-Spine forces (ASIS, upper and lower, left and right), and pelvis rotation were analyzed. Results: Average peak abdominal pressures were smaller in both nominal and moderate recline positions in the BPB (25°: 73.7 kPa, 45°: 82.5 kPa) compared to the no-BPB conditions (25°: 168.4 kPa, 45°: 339.1 kPa). In the 45° recline no-BPB conditions, both the peaks of the lap belt force and ASIS forces occurred early and a rapid reduction in those forces followed. This change in the lap belt and ASIS forces accompanied a rearward rotation of the pelvis. During the reduction of ASIS and lap belt forces, there was an increase in abdominal pressure suggesting that the lap belt moved upward, off the ASIS, and into the abdominal pressure sensor. There was a slight reduction in head and knee excursion with the PPT. These results suggest the presence of submarining in the 45° recline no-BPB conditions but not in the 45° recline with the BPB. Conclusions: The BPB could be beneficial when the seatback is moderately reclined. The differences during the moderate recline between the BPB and no-BPB conditions also indicate that the BPB could prevent submarining in moderately reclined seats.
... Or, les dispositifs de protection actuels, tels que les ceintures de sécurité et les airbags, sont conçus pour une position de conduite. Ils pourraient nécessiter des modifications afin de conserver le niveau de protection actuel pour de nouvelles positions d'occupant (Dissanaike et al. 2008). ...
Thesis
Full-text available
Des efforts de recherche et développement considérables portent actuellement sur des véhicules automatisés qui pourraient libérer les conducteurs des tâches de conduite. Le siège et l’intérieur de l’habitacle pourraient être modifiés pour mieux accommoder les activités autres que la conduite, telle que dormir, lire et travailler etc. Cependant, même si un grand niveau de sécurité est attendu pour ces futurs véhicules, des accidents continueront à survenir. Les dispositifs de protection actuels sont conçus pour une position de conduite. Ils pourraient nécessiter des modifications afin de conserver le niveau de protection actuel pour de nouvelles positions d’occupant. Cette thèse vise à identifier les risques et les opportunités en termes de protection de l’occupant associés à de nouvelles positions pouvant être introduites avec les véhicules automatisés. Sur le plan méthodologique, elle s’est largement appuyée sur les modèles humains numériques pour le choc qui se sont révélés comme un outil pertinent d'évaluation du risque. Une attention particulière a été portée à l'évaluation de la validité des modèles après repositionnement. Les travaux ont permis de mieux comprendre les mécanismes de retenue dans des positions semi-allongées en choc frontal. Ces positions apparaissent critiques avec une retenue délicate du bassin ou un chargement de la colonne lombaire selon l’angle d’assise. Une sensibilité importante à la position initiale du bassin a également été observée. Ces résultats pourront être utilisés afin d’aider à concevoir et à évaluer des nouveaux dispositifs de retenue. Afin de mieux connaître la posture de confort dans ces positions inclinées, une étude expérimentale a été réalisée à l’aide d’un siège multi-réglable. Ces expérimentations ont permis d’une part d‘identifier des configurations de siège de confort, et d’autre part d’établir les relations entre ces configurations de siège et la position du squelette interne, et en particulier celle du bassin. Ces résultats pourront notamment aider au positionnement des occupants lors d’essais physiques ou numériques. Dans l’ensemble, ces travaux montrent l’interaction forte entre le confort et la sécurité pour la conception de nouveaux habitacles automobiles.
... Tests concerning the position of the passenger with the seat fully reclined are omitted in standard procedures. It was found that a partially reclined seating position was the most comfortable for travelers, and also the most frequently chosen option [2]. However, different seat positions cause the unsatisfactory operation of the restraining system, which is designed for a specific position of a driver and passengers. ...
Article
Full-text available
Safety tests are generally performed in accordance with strict procedures that involve the use of a carefully positioned dummy. Safety tests are rarely conducted with the occupant being in a non-standard position. In real life driving, occupants, especially passengers, choose a more comfortable reclined position, and in such a case the body dynamics are different from those investigated in the standard safety test. Furthermore, with the rapid development of autonomous vehicles, which provide the possibility of the position of occupants being unrestricted, the investigation of "out of position" body kinetics is becoming more important. The presented study aimed to evaluate body dynamics with various seatback reclinations. Body dynamics were verified by simulating frontal impact on a sled system with the use of a standard 50 percentile Hybrid III dummy. Points of interest located on the dummies head, neck, pelvis, and legs were traced, which allowed its trajectory to be evaluated. Additionally, the maximal extrusion and the time of motion were evaluated. It was found that the maximal extrusion in the longitude direction is the same for semi and fully reclined seats. Furthermore, a reclined seat causes head rotation, which can result in neck injuries.
... Furthermore, current seatbelts are designed to load the strong parts of the occupant's body, traveling across the pelvis, over the shoulder, and across the chest, allowing a controlled forward motion during the crash (Adomeit and Heger, 1975;Adomeit, 1977). Any occupant position that is not upright, e.g., reclined or supine, compromises loading and control of the pelvis and chest, with submarining (the pelvis sliding under the lap belt, causing the lap belt to intrude into the soft abdomen) as a likely consequence (Dissanaike et al., 2008;McMurry et al., 2018;Boyle et al., 2019). ...
Article
Full-text available
In future fully automated vehicles, sleeping or resting will be desirable during a drive. While a horizontal position currently appears infeasible, a relaxed seating position with a reclined seatback and an inclined seat pan which enables a safe, comfortable position for sleeping or resting is possible. However, the inclined seat pan increases the forces and moments acting on the lumbar spine of the occupant and thereby the risk of lumbar vertebra fractures in a frontal crash. An energy management system integrated into the longitudinal seat adjustment (a seat track load limiter: STLL) that can reduce this risk should be investigated. When evaluating the injury reduction potential of a new restraint system such as a STLL it is important to include variations in both occupant size and crash severity. Otherwise, there is a risk of sub-optimizing, that is, the restraint system is only working for a limited number of situations. The restraint systems addressing these variations are normally referred to as adaptive restraint systems. The first objective of the study is to develop an activation strategy (adaptive release time of the STLL) for different crash severities and occupant sizes, making full use of the available stroke distance without bottoming out the STLL. The second objective is to evaluate the potential of the adaptive STLL to reduce the risk of lumbar vertebra fractures by comparing it to 1) a fixed seat and 2) a passive version of the STLL. Simulated frontal impacts were performed with two male SAFER human body models (HBMs) as occupant surrogates: mid-sized (80 kg and 1.8 m) and large (130 kg and 1.9 m). Three crash pulse severity levels were evaluated: low (40 km/h), medium (50 km/h), and high (56 km/h) impact speeds. The fracture risk was evaluated for the five lumbar vertebrae (L1–L5) in three different seat conditions: 1) a seat fixed to the sled, 2) a passive STLL that moves when a given force is exceeded, and 3) an adaptive STLL which moves at a time that depends on the occupant mass and crash pulse severity. The risk for lumbar vertebra fracture increased with crash pulse severity, while HBM size had no effect on risk. For all conditions, the passive STLL reduced injury risks compared to the fixed seat, and the adaptive STLL reduced risk even further.
... In consequence, the odds of mortality were the greatest for the fully-reclined seatback. However, a partially reclined seatback, although rated with lower mortality, is represented by a larger population, therefore it represents a significant health concern [7,8,11]. The most a knee bolster [44][45][46][47][48]. ...
Article
Full-text available
Presently, most passive safety tests are performed with a precisely specified seat position and carefully seated ATD (anthropomorphic test device) dummies. Facing the development of autonomous vehicles, as well as the need for safety verification during crashes with various seat positions such research is even more urgently needed. Apart from the numerical environment, the existing testing equipment is not validated to perform such an investigation. For example, ATDs are not validated for nonstandard seatback positions, and the most accurate method of such research is volunteer tests. The study presented here was performed on a sled test rig utilizing a 50cc Hybrid III dummy according to a full factorial experiment. In addition, input factors were selected in order to verify a safe test condition for surrogate testing. The measured value was head acceleration, which was used for calculation of a head injury criterion. What was found was an optimal seat angle −117°—at which the head injury criteria had the lowest represented value. Moreover, preliminary body dynamics showed a danger of whiplash occurrence for occupants in a fully-reclined seat.
... New vehicle interiors will likely be needed to accommodate these activities and reclined seats were found desirable in several studies [2]. However, based on accident data, Dissanaike et al. [3] observed that reclined positions improperly used in current vehicles were associated with increased mortality. Current restraint systems are designed and evaluated using Anthropomorphic Test Dummy (ATD) in a nominal seating position (i.e. 25 degrees manikin torso angle) [4]. ...
Article
Full-text available
Current highly automated vehicle concepts include reclined seat layouts that could allow occupants to relax during the drive. The main objective of this study was to investigate the effects of seat pan and pelvis angles on the kinematics and injury risk of a reclined occupant by numerical simulation of a frontal sled test. The occupant, represented by a detailed 50th percentile male human body model, was positioned on a semi-rigid seat. Three seat pan angles (5, 15, and 25 degrees from the horizontal) were used, all with a seatback angle of 40 degrees from the vertical. Three pelvis angles (60, 70, and 80 degrees from the vertical), representing a nominal and two relaxed sitting positions, were used for each seat pan angle. The model was restrained using a pre-inflated airbag and a three-point seatbelt equipped with a pretensioner and a load limiter before being subjected to two frontal crash pulses. Both model kinematic response and predicted injury risk were affected by the seat pan and the pelvis angles in a reclined seatback position. Submarining occurrence and injury risk increased with lower seat pan angle, higher pelvis angle, and acceleration pulse severity. In some cases (in particular for a 15 degrees seat pan), a small variation in seat pan or pelvis angle resulted in large differences in terms of kinematics and predicted injury. This study highlights the potential effects of the seat pan and pelvis angles for reclined occupant protection. These parameters should be assessed experimentally with volunteers to determine which combinations are most likely to be adopted for comfort and with post mortem human surrogates to confirm their significance during impact and to provide data for model validation. The sled and restraint models used in this study are provided under an open-source license to facilitate further comparisons.
... However, this is set to change in autonomous vehicles as new seating positions might be preferable with the introduction of new interior designs (Jorlöv et al. 2017;Lopez-Valdes, et al. 2019) Studies show that reclined seating positions might be the most desirable among HAV occupants. However, these seating scenarios, which have a greater potential for submarining and other traffic-related injuries (Dissanaike et al. 2008;McMurry et al. 2018), will pose a challenge for currently existing passive safety systems. ...
Article
Objective Self-driving technology will bring novelty in vehicle interior design and allow for a wide variety of occupant seating choices. Previous studies have shown that the increased risk of submarining exhibited by reclined occupants cannot be fully mitigated by changes in the seat configuration alone. This study aims to investigate the effects of three restraint countermeasures on cases with marginal submarining events and estimate their effect on submarining risk and injury prediction metrics. Methods Vehicle environment frontal crash Finite Element (FE) simulations were performed with the two simplified Global Human Body Model Consortium (GHBMC) occupant models: small female and midsize male. The baseline occupant restraints consisted of a frontal airbag, a seatback-integrated 3-point belt with a lap belt anchor pre-tensioner, and a retractor-mounted pre-tensioner and load limiter. Based on submarining thresholds identified in previous studies, three baseline configurations were identified for each occupant size. For each baseline case three restraint system modifications were evaluated. The modifications consisted of the introduction of a pelvis restraint cushion airbag (PRC), the use of a knee airbag (KAB) and the modification of the of the passenger airbag location (PAB). Simulations were performed using the USNCAP 56 km/h frontal crash pulse. Occupant kinematic data was extracted from each simulation to investigate how changes in the restraint system configuration affects submarining. Results Overall, in only one of the investigated cases did the proposed restraint modification prevent submarining occurrence, however each of the restraint modifications reduced the pelvis excursion over the baseline scenario. The presence of the PRC airbag showed the highest reduction in pelvis forward excursion for the female model. The presence of the KAB and the modified location of the PAB also contributed to reductions in excursion to a smaller degree. For the male surrogate, the KAB showed the highest reduction in pelvis forward excursion. The presence of the PRC led to a reduction in the lumbar spine shear force. Conclusions Submarining may be a major challenge to overcome for reclined occupants in autonomous driving systems. This suggests that there may not be a single generalizable currently-existing countermeasure able to effectively prevent marginal submarining cases in reclined positions.
Article
To study the safety of drivers with different sitting positions in intelligent vehicle collision, the slide model of SUV was established and the precision of the model was verified by slide test. The simulation model of driver's attitude was established by THUMS. According to the results of post mortem human surrogate (PMHS), the sitting postures of THUMS at different seat backrest angles were adjusted and the drivers’ injuries of three sitting postures in frontal collision were analyzed. Simulation results show that when the driver was in semi-recumbent and reclining posture, the protective effect of the airbag on the head was obviously reduced in collisions, and the head and chest will be seriously damaged due to the large seat backrest angle, resulting in increased distance between the head and the wheel. Besides, the tilting sitting posture leads to the risk of sunken seat in the collision. Therefore, with the development of autonomous driving technology, not only should intelligent vehicles meet occupants’ comfort requirements, but the collision safety caused by the change of sitting postures should be considered.
Article
Automotive safety devices, such as airbags and seatbelts, are generally designed for optimal performance when occupants adopt a "nominal" upright anatomical sitting position. While a driver's sitting behavior is largely influenced by the requirements of driving, a passenger may adopt any number of non-nominal positions and behaviors. Very few studies have investigated the behaviors that teen and adult passengers actually adopt. The present study investigates self-reported nonnominal sitting in passengers and quantifies the influence of age and anthropometrics on these behaviors. A better understanding of passenger behavior is a timely research topic because advanced sensors may eventually allow better detection of non-nominal sitting and the advent of autonomous vehicles increases the number of passengers and seating options. Ten online survey questions were created to assess how frequently non-nominal sitting was adopted. Results were obtained from 561 anonymous participants, ranging in age from 14 to 83 years old. Analyses included 1) averages for each question, 2) a statistical linear mixed model to test for the influence of age and height on responses, and 3) correlations between all questions. Statistical significance was set at p<0.05. In summary, there was a sizable percentage of participants who self-reported behaviors or sitting positions that potentially increase risk of injury. Younger subjects were significantly more likely to adopt non-nominal sitting. Shorter subjects adopted non-nominal foot position more often, while taller subjects' knees were significantly closer to the dash. Participants opted not to wear their seat belt in the rear seat more than the front seat.
Article
Full-text available
To assess the efficacy of occupant protection systems, the authors measured the mortality reduction associated with air bag deployment and seat belt use for drivers involved in head-on passenger car collisions in the United States. They used a matched case-control design of all head-on collisions involving two passenger cars reported to the Fatality Analysis Reporting System in 1992-1997, and driver mortality differences between the paired crash vehicles for air bag deployment and seat belt use were measured with matched-pair odds ratios. Conditional logistic regression was used to adjust for multiple effects. There were 9,859 head-on collisions involving 19,718 passenger cars and drivers. Air bag deployment reduced mortality 63% (crude odds ratio (OR) = 0.37, 95% confidence interval (Cl): 0.32, 0.42), while lap-shoulder belt use reduced mortality 72% (OR = 0.28, 95% Cl: 0.25, 0.31). In a conditional logistic model that adjusted for vehicle (rollover, weight, age) and driver (age, sex) factors, air bags (OR = 0.71, 95% Cl: 0.58, 0.87) and any combination of seat belts (OR = 0.25, 95% Cl: 0.22, 0.29) were both associated with reduced mortality. Combined air bag and seat belt use reduced mortality by more than 80% (OR = 0.18, 95% Cl: 0.13, 0.25). Thus, this study confirms the independent effect of air bags and seat belts in reducing mortality. Am J Epidemiol 2001;153:219-24.
Article
Full-text available
To assess the efficacy of occupant protection systems, the authors measured the mortality reduction associated with air bag deployment and seat belt use for drivers involved in head-on passenger car collisions in the United States. They used a matched case-control design of all head-on collisions involving two passenger cars reported to the Fatality Analysis Reporting System in 1992-1997, and driver mortality differences between the paired crash vehicles for air bag deployment and seat belt use were measured with matched-pair odds ratios. Conditional logistic regression was used to adjust for multiple effects. There were 9,859 head-on collisions involving 19,718 passenger cars and drivers. Air bag deployment reduced mortality 63% (crude odds ratio (OR) = 0.37, 95% confidence interval (CI): 0.32, 0.42), while lap-shoulder belt use reduced mortality 72% (OR = 0.28, 95% CI: 0.25, 0.31). In a conditional logistic model that adjusted for vehicle (rollover, weight, age) and driver (age, sex) factors, air bags (OR = 0.71, 95% CI: 0.58, 0.87) and any combination of seat belts (OR = 0.25, 95% CI: 0.22, 0.29) were both associated with reduced mortality. Combined air bag and seat belt use reduced mortality by more than 80% (OR = 0.18, 95% CI: 0.13, 0.25). Thus, this study confirms the independent effect of air bags and seat belts in reducing mortality.
Article
Context Approximately 10 million cars with automatic shoulder belt systems are currently in use in the United States. However, reports on the effectiveness of such restraints have yielded conflicting results.Objective To determine the effectiveness of automatic shoulder belt systems in reducing the risk of injury and death among front-seat passenger vehicle occupants.Design, Setting, and Subjects Analysis of data collected from the 1993-1996 National Highway Traffic Safety Administration Crashworthiness Data System on front-seat occupants involved in 25,811 tow-away crashes of passenger cars, light trucks, vans, and sport utility vehicles.Main Outcome Measures Death and serious injury to specific body areas by use of manual lap and shoulder belts, automatic shoulder belts with manual lap belts, or automatic shoulder belts without lap belts, compared with no restraint use.Results Use of automatic shoulder belts without lap belts was associated with a decrease in the risk of death vs no restraint use but was not statistically significant for all crashes (odds ratio [OR], 0.66; 95% confidence interval [CI], 0.42-1.06) or for frontal crashes (OR, 0.71; 95% CI, 0.38-1.35) after adjustment for occupant age, sex, vehicle year, airbag deployment, estimated change in vehicle speed during the crash, and principal direction of force. This association was significantly weaker than the 86% lower risk observed for use of automatic shoulder belts with lap belts (OR, 0.14; 95% CI, 0.07-0.26 vs no restraint; P<.05). Use of automatic shoulder belts without lap belts was associated with an increased risk of serious chest (OR, 2.66; 95% CI, 1.11-6.35) and abdominal (OR, 2.06; 95% CI, 1.004-4.22) injuries for all crashes.Conclusions These data indicate that improperly used automatic restraint systems may be less effective than properly used systems and are associated with an increased risk of serious chest and abdominal injuries. Given the continued widespread use of these automatic systems, educational programs may be warranted.
Article
Rationale: Although air bags have decreased the risk of serious injury from motor vehicle crashes, their deployment is not innocuous and can result in injury. The force of the deploying air bag can cause orbital blow-out fractures. We investigated the circumstances that predispose a crash occupant to this particular injury. Study design: The authors conducted a case series. Methods: A total of 150 orbital fractures occurred among 2,739 occupants in crashes included in the Crash Injury Research and Engineering Network (CIREN) database from January 1997 to July 2005. Ten orbital blow-out fractures attributed solely to air bag deployment were extracted and four reported in depth. Occupant, vehicle, and crash characteristics were reviewed for predisposing similarities and to investigate the mechanism of injury. Results: All crashes had air bag deployment and a frontal or near-frontal principle direction of force. Nine of 10 injured occupants were positioned within the air bag's deployment zone at the time of impact as a result of a forward seat track position, falling asleep at the wheel, being unrestrained, or having decelerated before impact. Six of 10 occupants experiencing orbital blow-out fractures were of shorter than average height. Based on rigorous crash reconstructions, the orbital blow-out injuries were felt to be causally related to air bag deployment. Conclusion: Air bag deployment may result in orbital blow-out fractures. Occupants positioned in close proximity to the air bag during its deployment phase appear to be at increased risk for orbital blow-out fractures.
Article
Most research on preventive health behaviors has focused on individual rather than groups of behaviors. This study examined interrelationships among multiple preventive health behaviors in different age and gender groups. From 1990 to 1992, Maryland residents were surveyed by telephone through the Behavioral Risk Factor Surveillance System. The study sample of 4455 was divided into 8 groups based on age (18-24, 25-39, 40-54, and 55+) and gender. Correlation and oblique rotated factor analyses were used to examine patterns of 8 to 11 preventive health behaviors in each age-gender group. Medical checkup and cholesterol test formed one behavioral cluster in the four male age groups. Breast and cervical cancer screening (mammogram, clinical breast examination [CBE], and Pap Smear) did not form one cluster until age 55 or older; Pap smear, CBE formed one cluster for women of all ages. Risk-taking behaviors were only prominent in the youngest age group: Seatbelt non-use, smoking, and drinking formed one cluster in younger males, and drinking and driving after drinking clustered in younger females. Screening and risk-taking behaviors form distinct groups, and behavioral patterns differ by age and gender. Public health programs should consider multi-behavioral approaches, and be sensitive to the gender and age of the target population.
Article
Approximately 10 million cars with automatic shoulder belt systems are currently in use in the United States. However, reports on the effectiveness of such restraints have yielded conflicting results. To determine the effectiveness of automatic shoulder belt systems in reducing the risk of injury and death among front-seat passenger vehicle occupants. Analysis of data collected from the 1993-1996 National Highway Traffic Safety Administration Crashworthiness Data System on front-seat occupants involved in 25,811 tow-away crashes of passenger cars, light trucks, vans, and sport utility vehicles. Death and serious injury to specific body areas by use of manual lap and shoulder belts, automatic shoulder belts with manual lap belts, or automatic shoulder belts without lap belts, compared with no restraint use. Use of automatic shoulder belts without lap belts was associated with a decrease in the risk of death vs no restraint use but was not statistically significant for all crashes (odds ratio [OR], 0.66; 95% confidence interval [CI], 0.42-1.06) or for frontal crashes (OR, 0.71; 95% CI, 0.38-1.35) after adjustment for occupant age, sex, vehicle year, air-bag deployment, estimated change in vehicle speed during the crash, and principal direction of force. This association was significantly weaker than the 86% lower risk observed for use of automatic shoulder belts with lap belts (OR, 0.14; 95% CI, 0.07-0.26 vs no restraint; P<.05). Use of automatic shoulder belts without lap belts was associated with an increased risk of serious chest (OR, 2.66; 95% CI, 1.11-6.35) and abdominal (OR, 2.06; 95% CI, 1.004-4.22) injuries for all crashes. These data indicate that improperly used automatic restraint systems may be less effective than properly used systems and are associated with an increased risk of serious chest and abdominal injuries. Given the continued widespread use of these automatic systems, educational programs may be warranted. JAMA. 2000;283:2826-2828
Article
This study determined demographic factors associated with reported seatbelt use among injured adults admitted to a trauma center. A retrospective chart review was conducted including all patients admitted to a trauma center for injuries from motor vehicle crashes (MVC). E-codes (i.e. ICD-9 external cause of injury codes) were used to identify all patients injured in a MVC between January 1995 and December 1997. Age, sex, race, residence zip code (i.e. a proxy for income based on geographic location of residence), position in the vehicle, and seatbelt use were obtained from the trauma registry. Forward logistic regression was used to identify significant predictors of seatbelt use. Complete data was available for 1366 (82%) patients. Seatbelt use was reported for 45% of patients under age of 25 years, 52% of those 25-60 years, and 68% of those over 60 years. Overall, seatbelt use was reported for 45% of men and 63% of women, as well as for 56% of Caucasians (i.e. Whites) and 34% of African Americans. In addition, seatbelt use was reported for 33% of those earning less than $20,000 per year and 55% of those earning over $20,000. Finally, seatbelt use was reported for 57% of drivers and 43% of passengers. Logistic regression revealed that age, female gender, Caucasian race, natural log of income, and driver were all significant predictors of reported seatbelt use. These results show that seatbelt use was more likely to be reported for older persons, women, Caucasians, individuals with greater incomes, and drivers. Seatbelt use should be encouraged for everyone; however, young people, men, African Americans, individuals with lower incomes, and passengers should be targeted specifically.
Article
We sought to investigate the effect of increased body weight on the risk of death and serious injury to occupants in motor vehicle crashes. We employed a retrospective cohort study design utilizing data from the National Automotive Sampling System, Crashworthiness Data System (CDS), 1993-1996. Subjects in the study included occupants involved in tow-away crashes of passenger cars, light trucks, vans and sport utility vehicles. Two outcomes were analyzed: death within 30 days of the crash and injury severity score (ISS). Two exposures were considered: occupant body weight and body mass index (BMI; kg/m2). Occupant weight was available on 27263 subjects (76%) in the CDS database. Mortality was 0.67%. Increased body weight was associated with increased risk of mortality and increased risk of severe injury. The odds ratio for death was 1.013 (95% CI: 1.007, 1.018) for each kilogram increase in body weight. The odds ratio for sustaining an injury with ISS > or = 9 was 1.008 (95% CI: 1.004, 1.011) for each kilogram increase in body weight. After adjustment for potentially confounding variables (age, gender, seatbelt use, seat position and vehicle curbweight), the significant relationship between occupant weight and mortality persisted. After adjustment, the relationship between occupant weight and ISS was present, although less marked. Similar trends were found when BMI was analyzed as the exposure. In conclusion, increased occupant body weight is associated with increased mortality in automobile crashes. This is probably due in part to increased co-morbid factors in the more overweight occupants. However, it is possibly also due to an increased severity of injury in these occupants. These findings may have implications for vehicle safety design, as well as for transport safety policy.
Article
The purpose of this study was to identify and analyze factors contributing to both airbag deployment and resulting head injuries (HIs) and to quantify the effect of airbag deployment on head injuries, in terms of odds of head injury and severity, in severe motor vehicle collisions (MVCs). Data were derived from severely injured (Injury Severity Score [ISS] > 12) drivers treated at Ontario's lead trauma hospitals (n = 1,272), and included all MVC driver deaths in the province (n = 665) from 1997-98. We conducted an epidemiologic description and a case-control study to compare drivers with and without HIs. Statistical analysis included Pearson's chi2, Wilcoxon rank-sum, and multiple logistic regression tests. Seventy-one percent of drivers were men, peaking in the 25- to 34-year age group. The most common impact involved multiple vehicles (62%) approaching each other. Overall, 59% of crashes had a frontal location of impact. HIs were significantly associated with a lower age (median, 36 vs. 43 years), seat belt use (53% vs. 59%), and airbag deployment (7% vs. 10%), with higher ISS (median, 34 vs. 22), ejection (20% vs. 10%), and mortality rate (44% vs. 35%). Airbag deployment was associated with higher age and seat belt use, and lower ISS, ejection, and deaths. Importantly, there were fewer HIs with the deployment of an airbag (64% vs. 73%) and a lower severity of HI. When logistic regression was used to control for the effects of possible confounders, airbag deployment was not statistically associated with one's odds of HI (odds ratio, 0.827; 95% confidence interval, 0.560-1.220), but ISS, age, and ejection were. Airbag deployment did not significantly lower a driver's odds of head injury in a severe MVC, but it did significantly lower the severity of head injury. This is a significant finding, given that 72% of our study population sustained a head injury and the importance of lowering the severity of these head injuries in terms of patients' ultimate outcome. The most important factor associated with head injuries was ejection, which nearly doubled a driver's odds of head injury (odds ratio, 1.759; 95% confidence interval, 1.201-2.577). This reinforces the supplementary protective effect of an airbag and that "buckling up" and keeping occupants in the vehicle is of primary importance in the prevention of head injuries.
Article
Light truck vehicles (LTV) are becoming more popular on US highways. This creates greater opportunity for collisions with passenger vehicles (PV). The mismatch in weight, stiffness, and height between LTV and PV has been surmised to result in increased fatalities among PV occupants when their vehicles collide with LTV. We reviewed cases of vehicle mismatch collisions in the Seattle Crash Injury Research and Engineering Network (CIREN) database to establish patterns and source of injury. Of the first 200 Seattle CIREN cases reviewed, 32 collisions with 41 occupant cases were found to involve LTV versus PV. The cases were reviewed by type of collision and vehicle of injured occupant: side impact of PV with LTV, front impact of PV with LTV, and front impact of LTV with PV. For each type of crash, injury patterns and mechanisms were identified. For side impact to PV, head and upper thorax injuries were frequently encountered due to LTV bumper frame contact above the PV side door reinforcement. For frontal impact to PV, severe multiple extremity fractures along with some head and chest injuries were caused by intrusion of the instrument panel and steering column due to bumper frame override of the LTV. Underriding of the PV when colliding with the LTV resulted in severe lower extremity fractures of the LTV occupant due to intrusion of the toe pan into the vehicle compartment of the LTV. The injuries and the sources identified in this case series support the need for re-designing both LTV and PV to improve vehicle compatibility. Revising Federal Motor Vehicle Safety Standard 214 to reinforce the entire door, consider adding side airbags, and re-engineering LTV bumpers and/or frame heights and PV front ends are possible ways to reduce these injuries and deaths by making the vehicles more compatible.