Content uploaded by Sharmila Dissanaike
Author content
All content in this area was uploaded by Sharmila Dissanaike on Jun 17, 2019
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 TRAUMA威Injury, 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 p⬍0.05, 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 TRAUMA威Injury, 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
(p⫽0.025). There was a significantly lower rate of seat belt
use in FR (57.8%) compared with UP (77.9%) ( p⬍0.0001).
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 ( p⫽0.0428). 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 ( p⫽0.0049). 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 ( p⫽0.87) or slightly reclined ( p⫽0.93) 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%
25⫹11% 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 TRAUMA威Injury, 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
