Se

aoe.

Fieure 5. A comparison of body kinematics of a 95th percentile dummy restrained by three different restraint
systems while decelerated at approximately 41 ft./sec.

tion to the occupant than the three-point, lap, or
diagonal systems. However, even this system
has installation variations which can be undesir-
able in use.

Few belts of the double-torso type are as yet
in use in U.S. automotive vehicles, although they
have long been used in aircraft. The Shelby-
American (Cobra) GT 350 and GT 500 cars, for
example, have utilized, since late 1966, a variation
of the double shoulder restraint harness. This
system, resembling an inverted Y, features an in-
ertia reel retractor, allowing full body motion
to reach controls, but locking at a predetermined
0.3g. to 0.5g. activation. As yet there have been
no reported accidents or injuries with this system.
This is similar in appearance to a Ford harness
presently undergoing biomechanical evaluation.
The Indiana State Police have been evaluating
a three-point harness with an Advanced Safety
Devices emergency locking retractor. Police of-
ficers involved in several accidents to date while
wearing this system have apparently avoided
serious injury. However, it should be noted that
there is no mass production experience (for auto-
mobiles) with inertia reels adjusted to lower
than 0.3g. to 0.5g. activation (aircraft reels are
adjusted to about 2.0g.). Many tests to date

18

have not demonstrated adequate reliability of
the reel.

In the study by Lister and Milsom of the
Road Research Laboratory in England,** of 355
individuals wearing full harnesses in accidents,
244 received no injury. Of the 111 receiving
some injury, 36 were to the head, 6 to the neck,
17 to the thorax including belt bruising, 5 to
the thigh, and the balance of 51 to the lower
extremities. However, information concerning
correlation with type of accident and impact
conditions was not provided. (A similar study
conducted in the United States, where vehicles
are larger and intruding environments offer
more distance between the occupant and environ-
ment during an impact, might demonstrate even
better protective results.) Deaths to occupants
were not reported; however, this study indicates
that the full-body restraint provides good pro-
tection in even severe accidents, compared to
other types worn. The authors conclude that
this type of harness, in comparison to the other
types studied, provided more restraint to the
upper torso, resulting in fewer head and neck
injuries but more chest injuries, including “bruis-
ing caused by the seat belt assembly.”

Other types of restraint devices, such as air-
bag systems, will be discussed in other papers.


tests, since most users do not have sufficient num-
bers of means to check their dummies. Never-
theless, the anthropomorphic dummy, despite its
limitations, offers a valuable testing device where
humans cannot be used and where the results are
not extrapolated too far.

Mathematical models of the human body are
an interesting approach and may be of great
usefulness to the design engineer in testing re-
straint systems under various known conditions.
The models by von Gierke and his associates
have made large contributions to our knowledge
of human responses in simulated vibration and
impact environments.* However the limiting
factor in such use is that the mathematical sys-
tem can be no more valid than the biological
inputs, and present knowledge of the biological
mechanisms of impact is much less comprehensive
than engineering and mathematical technology.
Human body simulation in this area is compli-
cated by the fact that the human body is of non-
linear, heterogeneous visco-elastic composition
which still defies precise mathematical quantifi-
cation, and human variability cannot be over-
emphasized.

Animal testing, particularly of primates similar
to man, is one approach which may provide valid
data based upon biological response in a living
organism. But there are also many problems
here. Extrapolation of data to the human cannot
always be validated. Structural differences such
as differing numbers of vertebra, lack of lumbar
curve, position of the foramen magnum (affecting
eg of the head), or even additional muscles not
found in the human, can affect results. Physio-
logical variances in the cardiovascular, neuro-
logical, or endocrine systems can play a part.
The animal researcher in impact can seldom test
all variables, and such considerations as the effect
of anesthesia upon response are often valid ques-
tions. Although considerable advances in micro-
instrumentation and measurements have been
made, these often in turn present questions of
artifact, e.g., how much effect upon the results
of the experiment did the surgical procedure
have? Yet, outside of the human ‘volunteer, the
closest_ material the physiologist can work with
is the living, functional biological system of the
non-human primate.

Human cadavers have been experimentally
used in impact in limited experiments but are
subject to many of the uncertainties of other

12

methods. To be at all realistic the body must
be either fresh or artificially manipulated, since
muscle tonus can be an important factor. Since
it is not a functioning biological system, discrete
trauma to body organs and soft tissue can only
be inferred. Problems of availability, limited
selection (usually old, small, infirm, and with
quite changed body fluids and tissues), security,
and preparation plague the researcher utilizing
cadaver subjects. Furthermore, research in pro-
gress by Life and Pince comparing living versus
embalmed tissues has already demonstrated that
there is considerable difference in skeletal tissue
reaction to impact, with embalmed cadaver skulls,
for example, “shattering” while living tissue
under identical force conditions may not even
fracture.**

Use of human subjects also has extreme limi-
tations for the study of body kinematics in im-
pact as well as impact trauma, since human
volunteers can not go above the subjective non-
injury (reversible injury) impact level, so this
realistic exploration of biomechanics is somewhat
restricted.

As a result of these and other problems (see
Severy, 1965, for further discussion) of valid
human simulation, many researchers utilize a
combination of techniques to extrapolate data to
obtain meaningful valid information. Carefully
controlled experiments using anthropomorphic
dummies, cadavers, primates, and humans under
identical impact conditions could do much to
resolve some of the problems brought out above.
Several attempts at this have been made. In an
unpublished 1964 study, Patrick and Daniel com-
pared the kinematics of the anthropomorphic
dummy, the flexed human cadaver, and the living
human volunteer with lap belt restraint in im-
pact. However, due to pain, welts over the
thighs, and lumbo-dorsal strain, the human run
had to be subjectively terminated at 12.9g. They
concluded that at relatively low impacts the
kinematics were similar.** But such may not be
the case at higher levels commonly encountered
in accidents. In two impact tests the authors
conducted at 30g. and 40g. the impacts were so
much more violent (lap belt only) than at 20g.
and 25g. that the neck was fractured in two cases,
with a four-inch transection of the cervical spine
occurring in one instance.** This was not pre-
dicted from dummy data.


70.

TH.

T.

.

76.

17.

78.

81.

. Srapp, J. P.: Tolerance to Abrupt Deceleration.

Sonnrac, Jz. R. W.: Intracranial Pressure in Ma-
caca Speciosa During Controlled Abrupt Deceleration.
In Aerospace Medical Association, Preprints of
Scientific Program, Annual Meeting, Washington,
D.C. pp. 162-163, 1967.

In
Collected Papers on Aviation Medicine. Butters-
worth Sci, Publ, London. AGARDograph No. 6,
pp. 122-139, 1955.

Srarr, J. P, and Lewis, 8. T.: Criteria for Crash
Protection in Armed Forces Ground Vehicles. HADC
TN. Holloman AFB, New Mexico, 1956,

Stapp, J, P.: Human Tolerance to Deceleration.
Amer. J. Surg, 93(4) : 734-740, 1957.

. Stapp, J. P.: Hearings before a Subcommittee of the

Committee on Interstate and Foreign Commerce,
House of Representatives, 85th Congress, First Ses-
sion, on Crashworthiness of Automobile Seat Belts.
#97108, U.S. Government Printing Office, 5-8 August
1957.

. Srapp, J. P. and Lewis, 8. T.: Human Factors of

Crash Protection in Automobiles. SAK Transactions
65: 488-492, 1957,

Starr, J. P. and Lewis, 8. T.: Experiments Con-
ducted on a Swing Device for Determining Human
Tolerance to Lap Belt Type Decelerations. AFMDC
TN-57-1, Holloman AFB, New Mexico, 1957.

Srapp, J. P. and Enrrerp, D, L.: Lap Belts Need
Sound Design. SAH Journal 66(9) : 30-81, Part II,
1958.

Starr, J. P.: Crash Injury Prevention, Part I.
Cincinnati J. Med. 89(1) : 1-5, 1958.

Srarp, J. P., et al.: Human Tolerance to Aircraft
Seat Belt Restraint. J. Aviation Med. 29(3): 187-
196, 1958.

Srarp, J, P.: After Seat Belts... What? In Cra-
gun, M. K. (ed.) Fifth Stapp Automotive Crash
and Field Demonstration, pp. 259-268, 1962.

Srarp, J. P.: Part II. Effects of Seat Belts: Man.

Environmental Biology, pp. 229. Federation of
American Societies for Experimental Biology.
Bethesda. 1966.

). SWEARINGEN, J. J. and Morrow, D. J.: Motion of the

Head and Trunk Allowed by Safety Belt Restraint
During Impact. Civil Aeronautics Medical Research
Laboratory, Columbus, 1956.

Swearrncen, J. J., Hasproox, A. H., Swyper, R. G.,
and McFappen,, E. B.:. Kinematic Behavior of the
Human Body During Deceleration. Aerospace Medi-

22

89.

91.

92.

93.

94,

. TouRIN, B.: Public Health Reports, 73: 381.

cine 32(2): 249 (Abstract). Civil Aeromedical Re-
search Institute Report 62-13, Okla. City, 1963.

. Taxtor, EB. R., CHANDLER, R, F., RHEIN, L. W., Ep-

warps, R. EL, and Carrer, V. L.: The Effects of
Severe Impact on Bears. Presented 34th Annual
Meeting Aerospace Medical Association, Los Angeles,
29 April-2 May, 1963.

Teare, D.: Post-Mortem Examination on Air Crash
Victims. Brit, Med. J. 2: 707-708, 1951.

Totiws, S. H.: An Unusual Injury Due to the Seat
Belt. J. Trauma 4; 897-399, 1964.

Wash-
ington, D.C.

. Tourn, B. and Garrerr, J.: Safety Belt Effective-

ness in Rural California Automotive Accidents.
Automotive Crash Research of Cornell University,
1960.

'. von Baur, V. and Erixsson, H.: Injuries Caused by

Safety Belts, Svensk. Lakartidn. 58: 141-148, 1961,

. VON GIERKE, H. E.: Biodynamic Response of the

Human Body.
Dee, 1964.
Wiuams, J. S, Lies, B, A, and Hare, H. W.:
Intra-Abdominal Injury from Seat Belts. J. Trawma
6: 303-315, 1966.

Wiu1aMs, R. D, and Saroent, F. T.: The Mech-
anism of Intestinal Injury in Trauma. J. Trauma
3: 288-294, 1963.

Worr, R. A.: The Discovery and Control of Ejection
In Automobile Accidents. J. Amer. Med. Assoc.
180: 114,

Woopnutt, R. B.: Traumatic Rupture of Pregnant
Uterus Resulting from Automobile Accident. Sur-
gery 12: 615-620, Oct. 1962,

Youne, J. W.: Recommendations for Restraint In-
stallation in General Aviation Aircraft. Federal
Aviation Agency OAM Report, AM 66-33, 1966.
Youne, J. W.: A Functional Comparison of Basic
Restraint Systems. Federal Aviation Agency OAM
Report 67-13, 1967.

Appl. Mech. Rev. 17(2): 951-958,

. Youna, J. W., Crauser, C., and McConvitre, J. 'T.:

Paper in preparation, 1967.

. Youne, J. W. and Witson, D.: Paper in preparation,

1967.

. Zawonowski, A. V., Rorustern, J. D., and Brown,

W. K.: Investigations in Human Tolerance to Lat-
eral Impact, Presented 36th Annual Meeting Aero-
space Medical Association, April 26-29, New York
City, 1965. Abstract: Aerospace Medicine 36(2):
168-169. Unpublished.


Fieure 1. Four basic restraint systems currently used in automotive vehicles.

Cocke and Meyer (1963) reported a severely
ruptured spleen as well as Jeft-anterior fractures
of the seventh and eighth ribs due to improper
looseness and high belt position. They noted
that “because of the patient’s heavy panniculus,”
she wore her seat belt loose and high across her
abdomen and lower rib cage, “transmitting the
impact force to the intraperitoneal organs rather
than to the heavy pelvic bones.”*

Aiken (1963) described a jejunal perforation
of the small intestine undetected until the sixth
day post-impact. He concluded that the mech-
anism was sudden compression of the intestine
between the seat belt buckle and the vertebral
column. ‘The only external indication of seat
belt. impingement was a “welt” across the lower
abdomen, below the umbilicus. Tolins (1964)
described a severe mid-abdominal wall contusion
and a perforation of the upper jejunum to a

man wearing a lap belt when his car crashed
into a tree.“

In a questionnaire Tolins (1964) submitted to
19 Naval Hospitals, one lap belt injury resulting
in a ruptured sigmoid colon was reported.

Intra-abdominal injury occurred more recently
to a front-seat passenger wearing a “snug” lap
belt when her Volkswagen was struck by an
oncoming car. She received a concussion, nasal
fracture, and lacerations to the cheek and left
elbow. There were numerous contusions and
faintly visible marks from the lap belt on the
lower abdomen and anterior superior spines.
Twelve hours later, surgery revealed a tear of
the jejunum about 8 inches below the ligament
of Treitz, which nearly severed the bowel. The
accident occurred about 2 hours following a large
meal and it was noted that the proximal portion
of the bowel was well-filled while the distal por-



Perhaps the ultimate in full-body protection is
the isovolumetric complete body encapsulation
developed by Lombard* for space use, and in
which an occupant might survive 200g. impact
forces. Such a system, however, would probably
not be popular among housewives or teenagers
on dates.

Legal Aspects: To provide seat belts is not
enough. For seat belts to be of any use, people
must be effectively convinced to wear them, and,
as injury data are beginning to demonstrate, they
must be worn correctly. As early motivation for
airplane pilots may have been simply to keep
from falling out of the aircraft, so also, perhaps,
a new motivation is occurring for the motorist.

It is of interest to note that recent court deci-
sions on injuries have ruled that the plaintiff's
failure to wear a safety harness—with which the
car was equipped at the time of the accident—
constituted contributory negligence. McRoberts
(1965) reports a case in which the jury reduced
the award the plaintiff would have received by
10 percent because of her negligence in not
wearing the belt provided.? In a more recent
Texas case the plaintiff’s recovery of damages
was reduced by 95 percent. The two legal prin-
ciples applying in the latter case are that “the
plaintiff has a duty to use reasonable care for
his own safety,” and that “where plaintiff’s prior
conduct does not bring about the impact or acci-
dent but has aggravated the ensuing damages,
plaintiff’s recovery is reduced to the extent that
his damages have. been aggravated by his own
conduct”.t While this may seem reasonable, the
opposite may now apparently be true. Cases
occur in which particular injuries are attributed
to the wearing of a seat belt, as, for example,
that which was reported recently in a Connecti-
cut newspaper (which must be viewed as specu-
lative by the researcher until discreet environ-

19

mental data in each instance are obtained to
define causes of injury). As has been pointed
out in this paper, there are numerous factors
which can play a part in contributing to a seat-
belt injury, but these may not always be due to
the characteristics of the belt itself, but rather
to such factors as improper wearing.

Vv. Summary

Although the seat belt restraint system has
been demonstrated to provide effective reduction
of injuries and fatalities in automobile accidents
by preventing ejection, with increasing usage of
belts by automotive occupants a pattern of in-
juries directly attributable to impingement on
the belt itself is becoming evident. This paper
has attempted to bring together the clinical evi-
dence concerning seat. belt injuries, discuss gross
biomechanical mechanisms of trauma, and eval-
uate the potential of four principal types of
restraint systems to produce injuries. New ex-
perimental research findings by the authors are
presented comparing the lap belt, diagonal, three-
point, and double-torso restraint systems in ex-
perimental primate impacts utilizing the 6571st
Aeromedical Research Laboratory’s Daisy De-
celerator, as well as discussion of findings related
to the effect of the lap belt in impact upon the
pregnant female and fetus. It is concluded that
the double-shoulder ‘harness probably offers the
greatest protection of the systems compared,
while the single diagonal belt. (without lap belt)
may be the most dangerous type in certain im-
pact situations. However, to allow freedom of
control reach, a reliable inertia reel is also neces-
sary for an effective system. It is emphasized
that the seat belt, properly installed and worn,
offers the single best protection for the automo-
tive occupant during an impact.



34,

36.

37.

39.

4,

42.

43,

44.

45.

46.

47,

48.

49.

BL.

52,

. KULOWSKI,

). MICHELSEN,

Hasprooxk, A, H,: Severity of Injury in Light Plane
Accidents. A study of Injury Rate, Aircraft Dam-
age, Aircraft Severity, Impact Angle, and Impact
Speed Involving 1596 Persons in 913 Light Plane
Accidents, Aviation Crash Injury Research, Flight
Safety Foundation, Report AvCIR 6-SS-105 (July),
1959.

. Hernert, D, D.: Med. J. Austr. 1: 61, 1964.

HowLanb, W.
B.: Fulerum Fractures of the Lumbar Spine.
Amer, Med. Assoc. 198(8) : 240-241, 1965.

Huerke, D. F. and Grkas, P, W.: Ejection—The
Leading Cause of Death in Automobile Accidents.
Conf. Proc., 10th Stapp Car Crash Conference.
Holloman AFB, pp. 156-181, 8-9 November 1966.

., Curry, J. L., and Burrineron, C.
J.

. Hurwirr, E. S. and Stiver, C. E.: A Ventral Hernia

Following an Automotive Crash.
Assoc. 194(7) : 829-831, 1965.
Jenxs, A. C.: Personal communication. 1966.

J. and Rost, W. B.: Intra-Abdominal
Injury from Safety Belt in Auto Accident, Report
of a Case, Arch. Surg. 73: 970-971, 1956,
Lawrence, J, M.: Seat Belt Liability: Texas.
fense Memo 7(7) : 52-58, 1966.

Lewis, 8, T. and Starr, J. P.: Human Tolerance of
ircraft Seat Belt Restraint. J. Aviation Med. 29:
187-196, 1958.

Lire, J. $, Prince, B, W., BRIAN, M., Hesexnern, P.
J., and Gasinx, J. W.: Comparative Responses of
Live-Anesthetized and Dead Embalmed Monkeys Ex-
posed to Impact Stress, Phase I. Space/Defense
TR 66-107, 16 Sept. 1966. (Submitted to Science
as Comparative Pathology of Live and Hmbalmed
Monkeys Exposed to Impact.)

Lanporen, S. and Ware, E,: Seat Belts and Accident
Prevention, Practitioner 188: 467-473, 1962.

Laster, R. D. and Mrsom, B. M.: Car Seat Belts:
‘An Analysis of the Injuries Sustained by Car Oéeu-
pants. Practitioner 191: 382-840, 1963.

Lomparp, C. F, and Apvanr, S. H.: Impact Protec-
tion by Isovolumetric Containment of the Torso.
Conf. Proc. 10th Stapp Car Crash Conference.
Holloman AFB, New Mexico, 1966.

MacVean, S. S.: Seat Belt Usage and Vehicle Oc-
cupancy Data. Ford Motor Oo. Technical Memo,
PRM 66-26, 9 August 1966.

McHenry, R. R.: Analysis of the Dynamics of
Automobile Passenger-Restraint Systems. Proc.
Seventh Stapp Car Crash Conference, O. C. Thomas,
1965.

McRoverrs, J. W.: Seat Belt Injuries and Legal
Aspects. Industrial Med. & Surg. 34: 866-869, 1965.
L, AuMaN, B, Tou, B. and
Mrrowext, J.: Dynamic Tests of Restraining Devices
for Automobile Passengers. Public Health Reports
79: 125, 1964.

Moretanp, J. D,: Safety Belts in Motor Cars, an
Assessment of Their Effectiveness. Ann. Occup.
Hyg. 5: 95, 1962.

Mosetey, A.: Research on Fatal Highway Collisions
Papers 1962-1963, Harvard Medical School, 1963.

J. Amer, Med.

De-

21

53.

55.

bt.

58.

59.

61.

64,

65.

66.

67.

. Parrick, L, M, and Danret, R, P.

Nawum, A. and Siscet, A.: Personal communication.
1967.

Comparison of
Standard and Experimental Windshields. L. M.
Patrick, ed., Mighth Stapp Car Crash and Field
Demonstration Conference, 1964, (Detroit, Mich.:
Wayne State University Press, pp. 147-166, 1966.)
Patrick, L. M., Mertz, H. J., and Krornt, ©. K.
Impact Dynamics of Unrestrained, Lap Belted, and
Lap and Diagonal Chest Belted Vehicle Occupants.
Conf. Proc, 10th Stapp Car Crash Conference, Hol-
loman AFB, New Mexico, pp. 22-53, 8-9 November
1966.

. Quinn, F. B., Jz: Are Seat Belts Enough? Gen.

Pract. 26: 101, 1962.

Raney, E, H.: Fetal Death to Non-Penetrating
Trauma of the Gravid Uterus. Presented at the
District VI Meeting of the American College of
Obstetricians and Gynecologists, Omaha, Nebraska,
30 September 1966.

Rusovits, F, E.: Traumatic Rupture of the Pregnant
Uterus from Seat Belt Injury. Amer. J. Obst. and
Gyn. 90(6) : 828-829, 1964.

Scuurman, M.: Metropolitan Toronto Coroner's Of-
fice Statistical Report. 1965.

. Scrwmier, S. and Woxr, R. A.: Leading Causes

of Injury in Automobile Accidents. Automotive
Crash Injury Research of Cornell University, Ithaca,
New York, 1962.

Severy, D. M.: Photographic Instrumentation for
Collision Injury Research. J. Soc. Motion Picture
and Television Engineers 67(2) : 69-77, 1950.

. Severy, D. M.: Human Simulation Techniques by.

Collision Researchers. Highth Stapp Car Crash and
Field Demonstration Conference. Wayne State Uni-
versity Press. Detroit, 1966.

. Smure, W. 8. and Kaurer, H.: A New Pattern of

Spine Injuries Associated with Lap Type Seat Belts.
U of M Medical Center Journal, Vol. 33, May-June,
1967.

Sxow, ©. ©. Syvver, R. G., Parce, G T., Sues,
T. K,, and Parry, W. L.: Trauma to the Urinary
System Caused by Abrupt Deceleration. Presented
Scientific Session on Urology, Annual Meeting Amer-
ican Medical Association, October 1967.

Snyper, R. G.: Civil Pilot Accident Experience with
High Performance Single Engine Light Executive
‘Type Aircraft. Paper presented at International
Air Safety Seminar, Flight Safety Seminar, Madrid,
Spain, November, 1966.

Snyper, R. G., SNow, ©. C., Crospy, W. M., Hanson,
P., Frxeo, J., and CHanprer, R.: Impact Injury to
the Pregnant Female and Fetus in Lap Belt Re-
straint. Presented at 10th Stapp Car Crash Con-
ference, July 1967; SAE Special Report #660801;
also FAA Report AM 68-24,

Snyper, R. G., Snow, ©. ©. Youne, J. W., Price,
G. T., and Hanson, P.: Experimental Comparison
of Trauma in Lateral (~G,), Rearward Facing
(+G,) and Forward Facing (—G,) Body Orienta-
tions When Restrained by Lap Belt Only. Aerospace
Med. 38 :889-894, 1967; FAA Report AM 69-13.



oe .

Ficure 3. Observed injury patterns in lap belt wearers.

driver and the 67-year-old woman passenger were
wearing snugly fitted three-point restraints. The
driver received a fractured sternum; the pas-
senger fractures of the left fifth, sixth, seventh,
eighth, and ninth ribs, and a severely lacerated
spleen. Since this woman had been taking
Coumadin ® daily for 2 years prior to this acci-
dent for anticoagulation, the hemorrhaging of
the spleen required unusual treatment.*® In an-
other case, Fletcher and Bragdon reported frac-
tures of the left sixth-ninth ribs and rupture of
the spleen.?*

A second case, involving a hyper-extension,
hyper-flexion cervical injury, was attributed by
Ebbetts to a three-point belt. In his opinion
trauma occurred “in a low-velocity impact in
which there was little danger of serious injury
to the patient had she not worn a seat belt.
Conversely, it was an injury which was definitely
aggravated by the use of a seat belt”.2*

Young, in a recent dynamic comparison of
dummy impacts conducted by the Federal Avia-
tion Administration involving eight different
restraint systems, found a significant difference

16

in effectiveness between a lap belt and three-
point or full-torso restraint in body kinematics.
He concluded that the double parallel shoulder
harness provided better restraint function than
the other types, including the three-point belt
“for at least two reasons: (a) the distribution
of applied loads to two belts is greater than the
same loads applied to a single belt, therefore less
belt stretch results in a greater restriction of
forward movement, and (b) certain combinations
of omnidirectional forces have a tendency to
cause a body torquing action with a single di-
agonal [stc, three-point] restraint that may re-
sult in a less efficient restraint function.” He
also found that the relative position of the seat
belt tie-down, which ultimately establishes the
seat-belt angle, is a significant factor; too for-
ward a tie-down location can seriously compro-
mise an otherwise good restraint system. Figure
5, adapted from Young, shows in body kine-
matics the relative restraint provided dummies
wearing three different systems (identical im-
pact patterns).


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uterine wall.”** This was fatal to the fetus. As
in the case reported above, absence of sign of
shock or intraperitoneal hemorrhage precluded
diagnosis for 2 days.

Hurwitt and Silver (1965) reported the case
of a woman developing ventral hernia 7 months
post-impact “presumably caused by the snubbing
action of the seat belt during the accident” which
occurred at an estimated speed of 60-70 mph
into an abutment. She also received fractured
transverse processes and subluxation of the fourth
lumbar vertebra over the fifth.5*

Fish and Wright (1965) noted two cases of
rupture of the pregnant uterus caused by seat
(lap) belts reported to them by Dyer.’®

The remark of one physician relating to an
impacted patient, that “there is no question that
the seat belt cost the life of the fetus, but there is
also no question that it saved the mother’s life,”
seems to sum up both the clinical evidence to
date and the experimental research which we

have conducted concerning impact to pregnant
females. Out of 30 cases of accidents involving
pregnant women wearing seat belts which one
of us (W. M. Crosby) has collected, death to the
fetus occurred in 12 cases (or nearly 50 percent,
since 11 have not yet delivered), even though the
mother survived. As will be shown, results of
our experimental tests on pregnant baboons have
approximated this experience, with resultant
death to the fetus at all levels from 20-40g., even
when the mother would have survived.

Cases which have come to our attention to
date are tabulated briefly in Table I, although
some are not yet completed.* Two-thirds of
these women. were riding in the right-front seat,
and the balance were driving the vehicle (except
for one woman 2 months pregnant involved in
an aircraft accident who was riding in the rear
of a tandem seat).*° Ages ranged from 19 to
30 years, and term of pregnancy from 6 weeks
to 40 weeks. Of these 30 cases, 24 were forward-

‘TABLE 1, SEAT BELT DMPACT INJURIES TO PREGNANT WOMEN

places [ooriton | novenom | para [age | for [eto — yeer——

o
FORWARD FACING DAPACT

@

a. Meadow ato | RF tap wo | + | Patan (rae: sunore
30 bre
‘2. Auto, Hole/Road | RF lap Over coy “ ° "
wep?)
3. to, Lap a | FATAL Gill + 12 hee)
4 Ata, tp | over a | FATAL (oul. placental ep.)
5. Auto, 30m | Driver we | Loa | oe Nove
nts ee
6. Head-Os tuto | Driver Lap a | None
1. auto, 20298 | RE Lap - [2 None
‘by 60 mp
8. auto, wr tap - -[s FATAL (v4-10 hr; Su.
‘oaaye)
2. Ato, F tap | tooee - | w Not yet delivered
10, Auto, ar? tap - | 2 | 2 FATAL (ul, 14 days)
14, Auto, BF? Lap - - |» FATAL (il, Coes, 3m.)
12, Auto, 38 moh | RF Le - fal - 1,2 | FATAL (torus ruptured)
Ti 35 mp
13, Ato, ide ar tap = fo | 6 [ae | nce wire «1-1/2 moe.»
‘atch
14, Hendon Ato | RF tap ~ fw fa a | aTaL qo, meracrantt
‘Treuna).
18. Had-on Auto| Driver tap [over tiy | 20 | a8 1 | Nonacry Not yet deivered
carer oat
16. Aigsuorer | ar tap frame’ fan | se | a | mmarated
17, Aatorraied | RE tap - [aw | ow O07)” | Nowet?y wo yt deivered
"ef side
18. Aste, - Lap - iu 1 | Nosec2y Not yotdoivered
18, Auto, - Lp? = |e | a2 | PaTAL bore 6 ne)
20, Auto, 36mph | RF ap? = |e | ae | paras tere repre)
21, Auto, : Lap? = [oe | tar | nooner not yet deivered
22. Neceat, tandem tae wl os None (Normal delivery
‘rinforans |r seat vi me)
23, Hendon tito [RE | lag Only so | 2 | FATAL uy a bea)
24, puto, Skid ner! pwgouy | = fo | - 1,2 | noaa(2) Not yok saivered
"REARWARD FACING DMPACT
a8. Driver tap | sme | oe | 30 | Nee
2. nF Lap - [0 | ow 1 | osecry Not yok deivered
a F tae au] 6 | gone] soe) net yt dered
28 RF Lap se | me] ante) | smn not yt dtvered
28. Driver Lap w oo) we ‘None(?) Not yet delivered
‘SIDE FACING IMPACT
30, Auto, pever | te bf |e ee term ty
roadaise

(ORF » nught Front

{Bimoter injurien: 0 = None, 1 = Contustons, 2 + More Serious Traum

5



tion was nearly empty. Disruption occurred at
the point where the head of the mass of food
had progressed at the time of impact.*®

Gerritsen, Frobese and Pezzi (1966) reported
the cases of two nearly identical injuries to two
lap-belted, obese women passengers in a head-on
collision, Both women were wearing lap belts
loosely fastened. One, in the left-rear seat, re-
ceived a laceration of the jejunum, multiple
lacerations of the mesenteric attachments of the
small bowel, and traumatic amputation of the
lower half of the omentum. The other woman,
riding in the right-rear seat, received large
laceration of the small bowel, lacerations of the
ileum and cecum, with division of the ileocecal
artery and a tear of the serosa of the sigmoid
colon. These authors theorized that the jerk of
the loose belts during impact allowed the lap
belt and buckle to go up the abdomen with a
shearing force, tearing the “mesentery and bowel
along its course, as well as causing contusions of
the abdominal wall.”7

Williams, Lies, and Hale (1966), in observing
intra-abdominal injury from lap belts in four
cases, note initial symptoms and physical findings
may be minimal. External abdominal trauma
may conform to the shape of the belts, but ab-
sence of such a lesion does not rule out internal
injury. Intraperitoneal damage is suggested by
increasing abdominal tenderness, gradual loss of
bowel sounds, and an otherwise unexplained ele-
vated white cell count. Peritoneal paracentesis
may confirm but cannot exclude trauma. Roent-
genograms may reveal rupture of the duodenum
or gravid uterus. Any abdominal organ may be
injured depending upon the position of the belt,
and the mechanism may be direct violence, tor-
sion or shearing, entrapment, or a combination
of factors. The small bowel and its mesentery
appear most vulnerable to direct force, while the
body flexion produces a shearing force which
may damage the duodenum or pancreas. Per-
foration of the small bowel or colon may occur
as the result of direct violence to a distended
loop or entrapment of a short segment to form
a closed-loop obstruction, according to their
assessment. They also concluded that splenic
injury from direct violence occurs only if the
belt is improperly applied.®*

Compression fractures to the lumbar vertebra
may occur as the individual jackknifes over the
lap belt. Garrett and Braunstein (1962) de-

scribed compression fractures to the lumbar
spine in eight cases.** In one recent case oc-
curring in the Detroit area, a 61-year-old woman
passenger in the right-front seat, wearing a snug
Jap belt, was injured when the car in which she
was riding struck another which crossed in front
in a left turn. The impact occurred at about
30 mph (1). This individual stated that upon
impact she braced herself with her right arm
against the instrument panel. Post-impact, she
complained of pain in the lower lumbar region,
and a compression fracture to the body of the
first lumbar vertebra was found.

Howland, Curry, and Buffington (1965) have
reported the unique case of a transverse fracture
of a vertebral body, which occurred in a 19-year-
old youth who ran into a steel pole head-on at
an estimated speed of 80 mph. This fracture,
discovered 1 month post-impact, was attributed
to high placement of the seat belt, allowing the
belt to act as a fulcrum, literally “splitting apart”
the vertebral body “similar to breaking a stick
over one’s knee.”*° A second case has been re-
ported by Fletcher and Bragdon, in which a
“splitting” fracture of the pedicles, transverse
processes, and lamina of the third lumbar ver-
tebra occurred in a (loosened) lap-belted 21-
year-old female who struck a semi-tractor truck
in a sports car at a high rate of speed.t Kaufer
and Smith, at the University of Michigan, have
found ten cases apparently involving a tension-
type mechanism previously not described.*

It should be noted that Nahum and Siegel, in
their unpublished study of over 150 accidents in
the Los Angeles area, have at present over 30
cases of seat belt injuries."*

1. Seat Belt Injuries to Pregnant Women:

Although traumatic rupture of the pregnant
uterus through external force has been reported
in accidents in which seat belts were not worn,
injuries to pregnant women due to the seat belt
only recently have been reported. Rubovits
(1964) first reported the traumatic rupture of a
6-months pregnant uterus in a woman whose car
was struck at 35 mph by another vehicle head-on
front quarter, when the other vehicle jumped a
divider. There was avulsion of the uterine mus-
culature at the site of the seat belt impact. This
was attributed to the force of the belt at the
anterior uterine wall being transmitted to the
fetus, “which was then blasted through the left


Fieure 4. Observed injury patterns in diagonal belt wearers (without lap belt).

Similarly, in a three-point (type II) restraint
system which is used in many 1967 automobiles,
and will be required for most 1968 models, the
location of the upper belt anchorage can be
critical in influencing effectiveness of the system.
For example, if the upper anchorage is too far
forward, relative to the seated occupant, the belt
angle will be such that it is too low on the shoul-
der, and the individual cannot only flex over it
and slip out, but will be torqued forward and
sidewards during the deceleration, which may
be particularly injurious. On the other hand,
if the anchorage location is too far to the rear,
relative to the seated occupant’s position, the
diagonal belt will impinge upon the neck, causing
discomfort even during normal driving. Such a
situation might, by creating pressures upon the
blood vessels of the neck and particularly the
carotid artery, as well as pressing upon nerves,
have a subtle but disastrous effect. In an impact
or rapid deceleration severe neck injury could
occur. This presents a dilemma to the package
designer who must consider seat positions for a
wide range of physiques, using limited attach-

1

ment points, as well as what to do with up to 27
separate belts in one vehicle. Improper posi-
tioning may also affect occupant acceptance and
future use of the three-point system if, upon first
experience, it is not comfortable, rubs against
the neck, or will not allow proper freedom to
reach controls.

Other than racing car accidents and a statisti-
cal study by Lister and Milsom,‘* no injuries to
automobile occupants wearing double shoulder
harnesses during an accident have been described
as yet.

Nevertheless, based on numerous studies by
previous investigators and experience in military
aircraft, the most effective belt system of the four
belt, systems considered here is a modification of
the full shoulder harness type such as is installed
in all commercial air transport flight deck pilot
positions to be worn during landing and takeoff
phases. Such a system, equipped with an inertia
reel retractor device, offers the compatible com-
bination of comfort, since the shoulder harness
reel allows free range of motion until the harness
is locked during deceleration, plus better protec-



was added to prevent artifactual iliac fracture.
Impact restraint consisted of a 1-inch 4,500-Ib.
test nylon webbing belt adjusted statically on
the seated animal to 1.5 kg. by tensiometer. The
belt angle was adjusted to 55°, and strain gauges
were mounted on each side of the lap belt. Ini-
tial animals were restrained for handling by
modified upper torso jackets, but these were
found unnecessary in subsequent runs.

Physiologic monitoring of intrauterine pres-
sure, maternal EKG, fetal EKG (four animals),
maternal blood pressure, and intra-abdominal
pressure (one animal), was recorded with an
eight-channel Sanborn and Ampex CF-100 tape
recorder. In addition, tracings of the seat-belt
tensions and g. profile were recorded on a Con-
solidated Electrodynamics Corporation recorder.
Photographic documentation included lateral and
overhead 16 mm. high-speed (2,000 fps) motion
pictures, still coverage, and 35 mm. color photo-
graphs of gross and microscopic trauma. In
subsequent tests a 1,000 fps, 35 mm, photometric
camera was also used. A Field Emission Flexi-
tron Flash X-ray System was triggered at im-
pact and at various time intervals ranging about
0.065 second after entrance of the sled into the
water brake, to study body organ displacement
at impact. Post-run whole body X-rays were
taken on each animal. Forces on the left and
right lap belt were measured in all forward-
facing impacts, and on the shoulder belt in the
two rearward-facing impacts, where a three-point
type of harness was utilized.

In the 45° seat pitch attitude it was found that
(a) during acceleration the abdomen is tensed,
raising the intrauterine pressure prior to impact;
(b) at approximately 0.050 second after the onset
of deceleration the animal is pressed down into
the seat causing a rise in intrauterine pressure
before “jack-kniving” begins; (c) following the
initial positive peak, the intrauterine pressure
drops sharply at about 0.100 second, and then
rebounds to a second, positive peak, averaging
about 400 mm. Hg at about 0.170 second. This
second peak is attributed to the sudden impinge-
ment of the uterus between the belt and the spine
when the animal is fully flexed anteriorly. In
one test, in which the animal was restrained by
a double shoulder harness system, there was an
absence of the second intrauterine pressure peak.
However, the maximum uterine pressure was 500
mm. Hg or very similar to that found in the

animals restrained by lap belt alone despite the
fact that the forces on the seat belt were very
much lower. This indicates that for the gravid
uterus, at least, increases in intra-uterine pres-
sures can be expected even when the body is
totally restrained from forward flexion.

Additional findings have included the presence
of post-impact bradycardia in both fetus and
mother. In one case, during surgical implanta-
tion of transducers the animal expired during
anesthesia. This animal, fully instrumented, was
nevertheless run as scheduled at 38g., forward-
facing, lap-belt restrained. This was the first
cadaver control to be run on the Daisy track,
and it is of interest to note that the intrauterine
pressures corresponded closely to those found in
the living animal. Three fetal deaths occurred
1.5 hours post-impact in the 20g. forward-facing
orientations. Two subsequent runs in the rear-
ward-facing position, considered to provide the
best protective support, have resulted in fetal
demise immediately post-impact at 40g., and fetal
demise within 24 hours post-impact at 20g. Al-
though these forces are well below human injury
tolerance levels for these body orientations, in
both of these there was no maternal trauma.
Initially, maternal neurogenic shock appeared to
be the most likely cause of death. However, to
date only two fetal deaths remain unexplained;
death in the others being attributed to fetal skull
fracture, cerebral hemorrhage, or placental sepa-
ration. Hopefully, such experiments may lead
to an explanation for similar unexplained fetal
deaths occurring in humans in automobile acci-
dents. As noted in Table I, 50 percent of the
forward-facing impacts in actual automobile
accident cases involving pregnant women which
have come to our attention have resulted in fa-
tality to the fetus, despite the lack of observable
trauma in most instances, Placental separation,
an expected finding, occurred in only two of the
tests to date. It should be emphasized that we
feel the lap belt, properly worn low over the
abdomen, nonetheless affords considerably more
protection to any pregnant occupant than no
restraint at all.

IIL. Results

A. Injury Comparison of Belt Systems: A
total of 45 baboon tests have been run under
controlled conditions and are summarized in
Table II. A major purpose of these tests has



AM 69-5

SEAT BELT INJURIES IN IMPACT

R. G. Snyder, Ph.D.
W. M. Crosby, M.D.
Cc. C. Snow, Ph.D.
J. W. Young, A.M.
P. Hanson, M.S.

Approved by Released by

M.D. P. V. Srzcex, M.D.

J. Rosert Diniz,
Cur, Crvin AEROMEDICAL Fepera, Am Surgeon

InstIToTE

March 1969

Department of Transportation

FEDERAL AVIATION ADMINISTRATION
Office of Aviation Medicine



Suerte

Froure 2. Comparison of belt loads in baboon subjects 30g. impact with four restraint systems.

tests have been run to be conclusive, but as will
be noted, even the loose, incorrectly placed lap
belt did not produce the extent of trauma ob-
served in the single diagonal belt restraint im-
pacts under identical force conditions, either in
the forward-facing or 90° left side impact.

One run at. 20g. utilizing a double shoulder
harness produced no injury to the animal. Fur-
ther runs at higher levels were not made because
extensive tests have been made of this configura-
tion in animal tests by other investigators.

Five decelerations from 40.4 to 22g. have been
made utilizing the three-point restraint (Type
II) system, including rearward-facing, forward-
facing, and one 90° left lateral impact. No
trauma, other than minor external belt contu-
sions, was found in either the 22g. or 30g. for-
ward-facing impact. No trauma was found in
either the 40g. or 30g. rearward-facing impacts.
This system appeared to offer much better pro-
tection than either the diagonal or lap belt only.
However, since it appeared that in a left side
impact a driver wearing a three-point system
could receive serious neck injuries, one 30g. run
was made in this body orientation. In this case,
findings included extensive areas of subpleural
hemorrhage involving the right chest wall from
ribs 2-7 and from ribs 3-6 and 11-18 on the left

10

side, along with large contusions of the shoulder
due to the belt. The most disturbing finding
was a total dislocation of the occipital-atlantoid
joint, accompanied by intramuscular hemorrhage
extending from the first to sixth cervical area of
the neck. Impingement of the neck upon the belt
was sufficient to cause death in this left 30g. lat-
eral impact. To determine further effects of
lateral impacts with the three-point (Type IL)
system, additional tests involving left and right
90° and 45° lateral impacts will be conducted.
Figure 2 provides a relative comparison of belt
loads in baboon subjects at 30g. impact with four
restraint systems.

As noted in Table II a number of lateral tests
have also been run utilizing lap belt restraint
only. These were reported 10 April 1967 at the
Aerospace Medical Association meeting in Wash-
ington, and were published in Aerospace Medi-
cine®" An unexpected finding in these tests was
the significant pancreatic hemorrhage occurring
in lateral impacts as low as 16.5g. Previous
human tests had reached a subjective tolerance
limit at only 9g." This trauma was determined
to be due to impact impingement from the lap
belt rather than post-mortem autolysis.

To our knowledge such trauma has not pre-
viously been described, and the significance of


been to experimentally determine the relationship
between body and seat orientation, force patterns,
and the effect of various restraint configurations
upon whole body injury tolerances.

Several investigators have found intra-abdomi-
nal injuries??7#98° believed to be related to loose,
improperly worn lap belts. In an effort to re-
produce injuries found clinically which might
be attributed to the shearing force (between lap
belt and spine, for example)* several subjects
were impacted with the lap belt purposely posi-
tioned high and loose. To avoid surgical arti-
facts, no physiological instrumentation was done
on any but the pregnant series. Animals were
sacrificed post-impact and gross and microscopic
necropsy accomplished.

Two forward-facing impacts were run at 34.2¢.
and 30g. At 30g. the impact, even with the lap
belt worn loosely and positioned high on the
abdomen, produced no significant trauma. The
animal, terminated post-run, was found at nec-
ropsy to have a belt contusion with subcutaneous
hemorrhage, hemorrhage at the head of the
pancreas, bilateral hemorrhage of the kidney,
pelvis, and uterine subserosal congestion. At
34.20. the impact was fatal, mainly due to the
rupture of a major neck vessel. There was also
moderate hemorrhage of the anterior bladder,
bilateral perirenal hemorrhage, avulsion of the
abdominal muscles at the pubis, severe transverse
lacerations (artifact) of the buttocks, and con-
tusion and subserosal hemorrhage of the neck of
the uterus. The lap belt caused a severe trans-
verse contusion, 3 centimeters wide across the
lower abdomen. In each case the lap belt re-
strained the animal in the seat. This is par-
ticularly noteworthy because the baboon has a
slightly higher center of gravity than the human,
and thus may be expected to flex even more than
the human.

In one 31g. impact in the 90° left lateral posi-
tion, the loose high position of the belt resulted
in a.ruptured uterus, peritoneal tear of the prox-
imal rectum, and slight areas of hemorrhage in
the right axilla and superior to the pubis.

Several investigators have described accidents
in which injuries were ascribed to the occupants’
wearing the single diagonal belt incorrectly,
under both arms. However, as was indicated
in the clinical background, and as will be further
noted in the discussion section of this paper, in-
juries of the thorax are particularly prevalent

in impacts involving wearers of the diagonal
belt. To compare the protective qualities and
possible injury patterns of various belt systems,
the diagonal belt has been utilized in three tests,
two forward-facing and one 90° lateral, all at
identical 80g. deceleration patterns. Because of
the apparent extensive trauma incurred by baboon
subjects wearing this belt system in comparison
to that occurring with the other systems studied,
a further series is planned to include impacts in
both left and right 45° and 90° lateral impacts,
as well as low-level forward impacts.

In each case the subject was not restrained by
the belt, and was flung from the seat, literally
hanging himself as rotation occurred about the
inferior axis of the belt, as seen in single-frame
high-speed photographic analysis. In one for-
ward impact the rotation caused the lower por-
tion of the body to pitch up about the belt so
that at one point in the impact sequence the body
was horizontal in the seat, then rotated so that
the head was on the seat with the feet straight
up in the air vertically, finally coming to rest
outside the belt at the foot of the seat. Since
this system does not use a lap belt, the lower
body is free to swing violently forward with a
torquing motion.

All three impacts with diagonal belts only
were instantly fatal to the subject. Injuries were
similar in each case, with a high proportion of
rib fractures and thoracic injury caused by im-
pingement upon the diagonal belt. In the 90°
left lateral impact (diagonal over left shoulder
as in driver position), necropsy showed the fol-
lowing trauma: complete avulsion, right pectoral
muscle; severe intramuscular hemorrhage, left
pectoral muscle; comminuted fractures, all ribs
left side 2-6; entire right chest wall presents
massive destruction with extensive hemorrhage;
hemorrhage of the intercostal muscles, left 1-3
ribs; ecchymotic hemorrhage of the pericardium;
laceration of apical lobe, right lung; anterior
mediastinal hemorrhage; hemorrhage of hylus of
liver; extensive bruising right axilla; pericap-
sular hemorrhage, right adrenal; five hemor-
rhages of spleen; and rupture of wall of the left
ventricle of the heart. Similar injuries, including
rupture of the spleen, fractures of 8-10 left ribs,
lacerations of the liver, ruptures of the sigmoid
colon, and hemorrhages of the pancreas, adrenals,
kidneys, and stomach, were found in the forward-
facing impacts with a diagonal belt. Too few



facing in impact orientation, five were rear-
ended, thus rearward-facing to the impact, and
one, hit broadside, was lateral to the impact
force. None of the rearward-facing impacts
caused more than contusions, although two
claimed symptoms of hyper-extension/flexion
(or “whiplash”) to the neck.

Most of the cases involved lap restraint, but
unfortunately, belt position and snugness was
not known for most of these. In one case, a
woman (40 weeks pregnant) was subjected to
an extreme bump (vertical force) when the car
in which she was riding hit a deep hole in the
road. She had placed the belt over the fundus,
and the jolt apparently caused placental sépara-
tion and a premature, but normal birth. In a
second case in which the Jap belt was placed
over the fundus in a woman 36 weeks pregnant,
the injuries in the subsequent accident were fatal
to the fetus, causing a deep laceration on the
posterior aspect of the uterus and extensive belt
contusions. In these cases, the high placement
of the belt probably contributed to the injuries.

In view of the additional protection claimed
by proponents of the diagonal restraint system,
it is of interest that two cases of extensive in-
juries to the mother have occurred in accidents
utilizing this restraint. In one instance, the
woman was a right-front seat passenger in a
small foreign car which had a head-on collision
with a larger one. Impingement of the diagonal
seat belt caused fractures of every rib on her left
side, rupturing her spleen, and causing massive
intra-abdominal hemorrhage. Post-impact, an
outline of the belt (in ecchymoses) was visible
extending from right shoulder to left thigh. The
fetus was stillborn 48 hours post-impact. The
diagonal belt did not prevent both her head and
knees from impacting the panel.

Injuries to the chest and head of a pregnant
woman also occurred in a second case, under
almost identical conditions; however, the outcome
of trauma to the fetus is still unknown.

Although we have found only 30 accident cases
thus far, the trend of abdominal impingement
by seat belts in accidents may be expected to
occur more often as more belts are worn, Ap-
proximately half of the clinical cases collected
to date involve a partial or complete separation
of the placenta with subsequent death of the
fetus.

2. Experimental Data: At the Tenth Stapp
Car Crash Conference in November 1966, we re-
ported the preliminary results of the first experi-
mental approach to impact injury to the pregnant
female.** Although this study was not concluded
until June 1967,"* a total of 11 of the 15 sched-
uled tests had been run.

This study was initiated as a joint effort of
the Federal Aviation Administration, USAF
6571st_ Aeromedical Research: Laboratory, the
University of Oklahoma School of Medicine, and
more recently by the Southwest Foundation for_
Research and Education, at the request of the
Air Line Pilots Association and the SAE S-9
committee, to determine the effects of abrupt
deceleration on the mother and her fetus when
restrained by a lap belt. It was calculated that
the crash landing of a jet transport, losing one
engine immediately after takeoff, at full gross
load, could impose resultant forces of 40g. at
45° (—Gx) upon a woman seated in the forward
section. This was the most extreme crash con-
dition estimated to be survivable, and formed
an initial basis for the first test. This was not
found to be survivable for the lap-belted baboon
subject, so the remainder of the forward-facing
tests were run at 20g. deceleration patterns.

For these tests the Daisy Decelerator at the
6571st Aeromedical Research Laboratory at Hol-
loman Air Force Base, New Mexico, was utilized,
with female adult Savannah baboons* (Papio
cynocephalus)** as experimental subjects. This
primate has a uterus simplex and a gestation
period of 180 days.

A. seat, scaled to fit the baboon, was oriented
in the 45° forward-facing body orientation (air-
craft) for the first seven tests, and at 0° (auto-
mobile) for the remaining seven tests. (One
test was a sham, with the animal undergoing all
preparation and instrumentation, but no impact.
run conducted.) A 2-inch Ensolite seat cushion

*The animals used for these experiments were law-
fully acquired and treated in accordance with the Prin-
ciples of Laboratory Animal Care issued by the Animal
Facilities Standards Committee of the Animal Care
Panel, U.S. Department of Health, Education, and Wel-
fare, Public Health Service, March 1963.

**At the beginning of these studies, this animal was
designated Papio doguera, but has since been assigned
the new taxonomic name Papio cynocephalus. It is
known as the Savannah baboon, rather than Kenya
baboon.


N

bal

=

a

2

10.

i.

12,

1B.

14,

1b.

16.

17.

. Arken, D. W.:

. ANON. :

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Intestinal Perforation and Facial
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ALpMAN, B.: Biodynamic Studies on Impact Protec-
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Auto Seat Harnesses, Consumer Reports,
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 Anon.: Nearly Two-Thirds of Drivers in Survey Do

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Backstrom, O.: Traffic Injuries in South Sweden
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Chirurgica Scandinavica, Suppl. 308, 1963.

. Bastraanse, J. C, and Bouwman, A. A.: Statistical

Study. Effectiveness
RAI-TNO, Instituut
Netherlands, 1966.
Birrett, J, H.: Safety Belts for Motor Vehicles in
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Bourke, G. J.: The Efficiency of Car Safety Belts.
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(of) Seatbelts, Rapport.
Voor WegtransportMiddelen,

. Brunivs, U. and Linporen, S.: The Effectiveness of

Safety Belts. An Analysis of 210 Belt Cases.
Med. 66(44) : 1500-1503, 1961.

CampseLt, B, J, and Krareerc, J. K.: Seat Belt
Effectiveness in the Non-Ejection Situation. Pro-
ceedings, Seventh Stapp Car Crash Conference, C.
©. Thomas, 1964,

Campsett, H. E.: The Automotive Seat Belt and
Abdominal Injury. Surgery 119: 591-592, 1964a.
Cocke, Jz., W. M. and Myer, K. K.: Splenic Rupture
Due to Improper Placement of Automotive Safety
Belt. J. Amer. Med. Assoc. 183(8) : 698, 1963.
Crospy, W. M., Snyper, R. G, Snow, C. CG. and
Hanson, Perer G.: Impact Injuries in the Pregnant
Female: I. Experimental Studies. Presented, Central
Association of Obstetricians and Gynecologists An-
nual Meeting, 14-16 Sept. 1967; Amer. J. Obs. & Gyn.
Vol. 101, No. 1, pp. 100-110; also FAA Report
AM 68-6, March 1968,

DeHaven, H., Tourtn, B., and Macrr, S.: Aircraft
Safety Belts: Their Injury Effect on the Human
Body. Orash Injury Research of Cornell University
Medical College, 1953.

DuBors, E. F.: Safety Belts Are Not Dangerous.
Brit. Med. J, 2: 605, 1952.

Epserrs, J.: Seat Belts and Cervical Spondylosis.
Pract. 188 : 802, 1962.

Exias, M.: Rupture of Pregnant Uterus by External
Violence. Lancet 2: 253-254, August, 1950.

Nord.

20

18.

19.

21,

23.

26,

27.

29.

30.

31.

32.

Eneserc, A.: Injuries Caused by Safety Belts. A
Contribution to the Discussion with Reference to an
Unusual Case. Svensk. Lakartidn. 58: 884-886, 1961.
Fisn, J. and Wriewt, R. H.: The Seat Belt Syn-
drome—Does It Bxist? J. Trauma 5(6): 746-750,
1965.

Fisuer, P.: Injury Produced by Seat Belts: Report
of 2 Cases. J. Occupational Med. 2: 211-212, 1965.
Fruetcuer, B. D. and Bragpon, B. G.: Seat-Belt
Fractures of the Spine and Sternum. JAMA 200(2):
177-178, April 10, 1967.

Frazier, R. G.: Effectiveness of Seat Belts in Pre-
venting Motor Vehicle Injuries. New England J.
Med. 264; 1254-1256, 1961.

Frepericks, R. H.: Progress in Safe Vehicle Design.
The Fifth Stapp Automotive Crash and Field Dem-
onstration Conference, The University of Minnesota,
DP. 225-240, 14-16 September, 1961.

| Frepertcks, R. H.: Barrier Collision Investigation

of Harness Restraining Systems.
enth Stapp Car Crash Conference.
©. C. Thomas, 1965.

Garrett, J. W.: A Study of Seat Belts in Wisconsin
Automobile Accidents. Cornell Aeronautical Labora-
tory, Inc. Rept. No. VJ-1823-R3, Sept. 1963.

Garrett, J. W. and Braunsrern, P. W.: The Seat
Belt Syndrome. J. Trauma 2: 220-288, 1962,
Gerritsen, R., Fronesr, A. §., and Prgzzr, P. J.:
Unusual Abdominal Injuries Due to Seat Belts. J.
of the Albert Hinstein Medical Center 14(1) : 68-66,
1966.

Gissane, W. and Butt, J.: A Study of Motor-Way
Fatalities. Brit. Med. J. 1: 75, 1964.

Goarr, E.: Road Accidents, Geigy, Basle, Switzer-
land (“Unfallopfer im Strassenverkehr” Series
Chirurgica Geigy No. 5, 1962). 1965,

Grime, G.: Seat Harness. Effect of a Harness on
the Movement of the Occupant of a Car During a
Head-on Collision. Auto Engr. 58: 12, 1968.

Hatey, J. L.: Personnel Restraint Systems Study,
Basic Concepts. AVvCIR 62-12, Dec. U.S. Army
Transportation Research Command, Fort Eustis,
Virginia. 1962.

Hansen, O, M. and Rasmussen, P. 8.: Traffic Acci-
dent with a Spleen Injury Associated with the Use
of a Safety Belt. Ugeskr. Laeg. 125: 771-778, 1963.

Proceedings, Sev-
Springfield, I. :

. HasBroox, A. H.: Design of Passenger “Tie-Down”.

“Some Factors for Consideration in the Orash-
Survival Design of Passenger Seats in Transport
Aircraft.” Report AvCIR 44-9-66, Aviation Crash
Injury Research of Cornell University, Flushing, N.
Y., 1956.


If it is true that some 70 percent of vehicle
occupants do not use restraints even when avail-
able, we may not see drastic improvements in
the accident injury and fatality statistics until
people are effectively convinced to use them.
Nevertheless, due to the overall increase in the
wearing of belts, the patterns of injuries which
may be identified as caused by the belt are be-
coming more clear. This makes possible assess-
ments of the protection offered and a need, not
previously as evident, to improve the belt systems.

Some idea of the sharp increase in injuries
attributed to the seat belt can be found by noting
that of the clinical reports referenced in this
paper, only three studies occurred prior to 1956,
and these were addressed to safety belt injuries
in aircraft ;1*°* yet over 20 clinical reports alone
have been concerned with this problem since
1961. This may only reflect the true incidence,
since most such cases are probably never reported
in the literature.

There currently are four principal configura-
tions of seat belts in automotive use: the lap
belt, the single diagonal belt, the three-point (or
combination of lap and diagonal), and the double
parallel combination of lap and double shoulder
harness (Fig. 1). “Lap belt” refers to a single
belt across the anterior aspect of the pelvic struc-
ture; “seat belt” refers to any combination of
lap and torso restraint. There are numerous
variations of the types, such as five-point, double-
vertical belts without lap belt, and shoulder belts
with inertia reels. Experimental systems now
under development and testing for future auto-
mobiles will probably use entirely different con-
cepts of restraint. For the purposes of this
paper, each of the four systems currently in use
will be examined for injury-producing charac-
teristics.*

Injuries caused by contact with the instrument
panel, steering wheel, or other environmental
surfaces will be discussed by other participants
of this symposium, and only those injuries which
may be directly attributable to the:seat belt itself
will be included here.

*Further tests relative to more advanced restraint
systems, including both the inverted-¥ yoke with inertia
reel and the air bag system, have been conducted since
these data were reported, but too recently to be included
in this paper. Preliminary primate impact data on
these will be reported at a later date.

II. Method and Materials

A. Clinical Background: Most cases docu-
mented in literature, describe intra-abdominal
consequences of seat-belt impact to the soft
tissues or neurological, cardiovascular, and en-
docrine organ systems, although skeletal trauma
may also occur.

Teare (1951) found in a 1951 Comet jet air-
liner crash in England numerous abdominal, as
well as thoracic, aortic ruptures which he at-
tributed to the snubbing action of the lap belt
with forced flexion of the torso.®*

DuBois reported in a 1952 study, among indi-
viduals involved in serious aircraft accidents
while wearing lap belts, 283 cases of intra-ab-
dominal injuries which could be attributed to
the belt, along with 32 cases of contusions along
the belt line.1*

DeHaven, Tourin, and Macri (1953) reported
an investigation of injuries sustained by 1,039
survivors of 670 light aircraft crashes. Except
for bruises and minor contusions attributable to
safety belts, they found no significant effect due
to severe snubbing action of the belt.“ A more
extensive survey by Hasbrook covering 1,965
individuals in 913 light aircraft accidents oc-
curring between 1942-1952 confirmed these con-
clusions.*+

In 1956, Kulowski and Rost reported a case
of a small bowel obstruction due to a large ad-
hesion of the terminal ileum to the right iliac
crest of the pelvis. Injury to the ileum by the
lap belt was proposed as the cause of the ad-
hesions.*°

Garrett. and Braunstein (1962) analyzed re-
ports of 944 injured occupants wearing seat belts
of which 26 of 150 serious lower torso injuries
might be attributable to the belt.*° They found:
(1) Seven had possible intra-abdominal injuries.
One had a ruptured pancreas and duodenum and
another had a contused bladder and kidney.
Four had abdominal wall contusions from their
seat belt. (2) Seven had pelvic injuries of which
six were moderate to severe fractures. Of these,
two had abdominal wall contusions from the lap
seat belt. (3) Twelve had lumbar spine injuries
of which eight were serious. One had abdominal
wall contusions due to the snubbing action of the
belt. (4) Lumbar muscle sprains or strains were
observed in 47 cases, and (5) Contusions or sore-
ness over the iliac crests, without apparent in-
ternal or skeletal injury, were found in 77 cases.


Some of the major breakthroughs in our
knowledge of acceleration have occurred through
accident or through purposeful studies in which
the researcher uses himself as a subject. Exam-
ples of this are Colonel Stapp’s sled ride of
632 mph to demonstrate that a human could
survive such forces of windblast and deceleration
in an aircraft ejection; Major Beeding’s rear-
ward-facing deceleration of 83g.; and, Lt. Colonel
Kittinger’s rotation during delayed free-fall from
86,000 feet. Obviously we can not experimentally
test restraint systems using a statistically valid
sampling of the human population including
elderly, infirm, babies and children, obese, etc.
But in another sense this is done through epi-
demiological studies of automobile accidents in
investigations conducted by researchers such as
Moseley in Massachusetts,°? Huelke and Gikas
in Michigan, and Nahum and Siegel in Cali-
fornia.** Such work is important to demonstrate
the value, or deficiency, of such things as re-
straint devices and plays an important role in
contributing to our knowledge and future design.

Human tolerance to lap belt crash forces has
been experimentally studied on the Daisy Track,
Swing decelerator, and Bopper, at Holloman Air
Force Base. Hasbrook, in 1956, rode the NACA
decelerator with a measured seat deceleration of
7g. and “probable” 14g. chest, resulting in bruis-
ing and lower abdominal complaints.** Subjec-
tive reactions found by Lewis and Stapp to
15-20g. impacts were complaints of abdominal
pain. They concluded that decelerative force
exceeding 10g., at 300g. per sec. rate of onset,
for 0.002 second duration would result in mini-
mal contusion over the hip region due to lap
belt impingement (7° p. 66). At 18g., with the
same time duration and rate of onset, in addi-
tion to contusions, strain of abdominal muscles
could be expected with accompanying soreness.
On one run reported to be at 26g., the highest
human voluntary impact of that series, using a
lap belt only, the subject complained of severe
epigastric pain persisting for 30 seconds, and
pain in the area of the thoracic vertebra con-
tinuing for 48 hours. Seat belt forces in this
case were 4,290 pounds. Impingement area of
the 38-inch nylon lap belt (with standard AF
hardware [16-inch length] was 48 sq. inches) and
average impingement area force was calculated
to be 89.3 psi. Subsequent human tests on the
Daisy Track have not exceeded 15g. forward-

18

facing with lap belt only. This is generally
considered to be the upper limit of the subjective
tolerable impact. A 30-mph barrier crash (equiv-
alent to a head-on crash of 40-60 mph) has been
found to impose seat belt loads on anthropo-
morphic dummies of 3,000-6,000 pounds. Higher
forces have been experimentally measured during
animal impacts.

Note that belt forces of 1,518-3,588 pounds
(31.0-74.7 psi) belt pressure at 0.001-0.008 second
duration at 15-23g. on abdomen were found in
the Lewis and Stapp tests of volunteers. Only
three of these subjects were reported (out of 19)
to have received belt bruises in the impingement
area, but two others were sore at the lower mar-
gin of the rib cage, one for 4 days, one for 2
weeks. However, these forces would probably
be close to the subjective tolerance limits, since
these subjects were all healthy young males. It
js important to note that a difference was found
in subjective tolerance not only between indi-
viduals, but within the same individual on dif-
ferent runs. In similar tests a subjective limit
of 9g. was found to be the highest voluntary
level in the lateral position.’ In the rearward-
facing position volunteers have been impacted
only while utilizing a full-torso harness.

A study of optimum restraint for the U.S.
Army resulted in a recommendation of trans-
verse design load factors of 45g. for 0.10 second
and 25g. for 0.20 second with harness loads for
a minimum of 0.10 second of 4,000 lbs. for
shoulder straps and 6,000 lbs. for the lap belt.**
Due to the higher g. loadings which are often
encountered in the automotive accident, automo-
tive seat belts (lap) are presently designed for
greater strength (4,000-6,000 lbs.) than aircraft,
which are presently only required to meet 2,000
lb.-loads in general aviation aircraft.

Many investigators speak of a “submarining”
action, in which the individual slides under the
belt in deceleration, which is one reason that
military restraint systems often use a fifth crotch
belt? Submarining may occasionally oceur in
aircraft, especially to an occupant wearing a
loose lap belt and tight shoulder harness. But
note that the impact angle may be quite different
from the horizontal force incurred in the typical
automobile crash. Also, while 50th percentile
anthropomorphic dummies may occasionally de-
scribe “submarining” kinematics, researchers



the pressure on the well-protected pelvic area”*
(p. 485).

This also is supported by Williams, et al. who
found that the shoulder belt “can produce a
more serious injury than the lap belt.” Al-
though about 80 percent of the 712 front-seat-
belted car occupants injured in a South Sweden
study were wearing the diagonal belt, the type
of belt used was not considered in an analysis
of the data. Significantly, of 60 injuries noted
(not defined as to whether related to the belt)
44 injuries occurred to occupants wearing the
diagonal.®

Lindgren has found cases of multiple fractures
of the ribs, fractured clavicles, sternum, a rup-
tured liver, and one case of rupture of the left
atrium of the heart attributed to the diagonal
type of belt. He also reported two of three fa-
talities in a study of 382 accidents comparing
injuries with different belt systems used. Lind-
gren raises the question, in reference to side
impacts occurring to drivers wearing diagonal
belts, “if the belt may not accentuate the violence
sustained by the driver’s pelvis when it is thrown
against the door during deceleration”.“*

There have been unsubstantiated reports of
occupants being decapitated by diagonal belts
in side impacts. However any such cases are
probably a result of other artifacts, not the belt
itself, Lindgren, for example, reports one such
case which appeared at first to have been due to
the belt, but which was later determined to be
due to the driver’s head being scissored by the
door.**

In an earlier study by Brunius and Lindgren
of 210 accidents to car occupants while wearing
belts, the pressure of the belt was considered not
to have caused any internal injuries. Hanson
and Rasmussen found one case of a ruptured
spleen attributed to a diagonal belt.*?

It is significant that the warning “This shoul-
der strap is not to be used without a lap belt” is
printed in the Owner’s Manual or on the labels
of standard three-point (type II) restraints in
U.S. production automobiles. To our knowledge,
our experimental tests with primates, still in-
complete, are the first experiments involving 1
living subject to be conducted with the diagonal
belt system only.

In a study conducted last year of 900 Dutch
accidents, Bastiaanse and Bouwman compared
the effectiveness of hip (lap), three-point, and

diagonal restraint systems. Although they re-
ported twice as much head injury for lap-belt
users as for users of other types, they found
three times as many chest and leg injuries for
diagonal and three-point users as for lap-belt
users.®

Backstrom, in analyzing 712 front-seat-belted
occupants in accidents in Sweden noted that
“chest injuries were relatively common among
car occupants,” occurring in 252 cases (14%)
(which he attéibuted to the steering wheel).°

Fletcher and Bragdon (1967) report an oblique
fracture of the sternum received by a 33-year-old
physician, striking a tree at about 35 mph in a
small Swedish car while wearing a diagonal belt.
They note that looseness of the belt permitted
several inches of forward movement of the thorax,
but prevented contact: with the steering assembly.
They conclude “this type of belt cannot guaran-
tee safety”.**

One of the earliest analyses of automotive seat
belt injuries was conducted by Brunius and
Lindgren® of 210 accidents between 1957-1960
in Sweden in which belts were worn. With the
exception of one belt breaking, one individual
slipping out of his belt and being thrown from
the car, and a third case in which the belt was

> too loose, they reported no internal injuries or

15

aggravation due to the belt (three-point type).
Lister and Milsom in England obtained data on
600 accidents in which 837 belted front-seat oc-
cupants were involved. They compared injuries
occurring with four types of belts—full harness,
lap and diagonal pillar fitting (three-point), lap
and diagonal floor fitting (three-point), and
diagonal only—finding an overall reduction in
expected injuries, in comparison with accidents
in which belts were not worn.** In Australia,
Birrell (1964) made a similar study.”

Injury patterns typical of accidents in which
the wearer was using a lap belt are shown in
Figure 3. Note the somewhat different pattern
and location of injuries when the wearer is using
a diagonal belt only, as shown in Figure 4.

Injury attributable to the thrée-point (type IT)
restraint system has been less frequently reported.
Fisher in 1965 described the first case of a splenic
rupture from use of a three-point combination
lap and diagonal belt. Ironically, the impact
forces involved were unusually small, a Volks-
wagen striking a Renault broadside at 5-10 mph
from a full stop. Both the 42-year-old woman



SEAT BELT INJURIES IN IMPACT

I, Introduction

A number of research and accident investiga-
tion studies have demonstrated that the seat belt
is a single most effective means of providing
occupant protection in a vehicular accident. By
preventing ejection, reported to be the leading
cause of both injury and death in accidents or
in restraining the occupant from being flung
about during the impact sequence, belts have
been shown to considerably reduce both the se-
verity of injury and fatality.° The conclusion
by Tourin and Garrett in 1960 that seat belts
“could save at least 5,000 lives a year and reduce
injuries by one-third,”** has since been supported
by similar findings relating to the value of the
seat belt by other investigators. Herbert con-
cluded that lap belts reduce injury 35 percent
and diagonal belts 80 percent;** Lister found
that seat belts could reduce injuries by 51 percent
in England ;** and here in Michigan, Huelke and
Gikas predicted in their study of fatal accidents
that “of 48 ejectees, 38, or 80 percent, would have
survived if they had been wearing only the lap
seat belt.”5’ It is thus somewhat ironic that evi-
dence is mounting that this protective device in
itself can be responsible for distinctive injury
patterns, one of which was first described as the
“seat belt syndrome” by Fish and Wright.’

The objective of this paper is to present recent
clinical and experimental research findings con-
cerning restraint system injuries, briefly compare
current systems of restraint as related to the
biomechanical mechanism, and suggest ways of
reducing the potential of this type of trauma.

Although seat belts have been used for over
50 years in aircraft, they have not had as uni-
versal acceptance on the ground. Most of the
early seat belt development has been directly in
response to aviation and aerospace requirements.

Presented, University of Michigan Medical School
Sesquicentennial Symposium on The Prevention of
Highway Injury, Highway Safety Institute, Ann Arbor,
19-21 April 1967.

Except for special vehicles, it has only been
during the past decade that the seat belt has
been utilized in the U.S. to any extent. Although
a form of lap belt was used earlier in some models
of the 1959 Nash reclining seat to retain occu-
pants while sleeping, they were first offered in
the U.S. as a safety device in late 1955 by Ford
and Chrysler. Since lap belts became standard
in U.S. cars a few years ago, and shoulder or
upper-torso restraints (type II) were optional
last year, considerably more individuals are
wearing belts. Both types will be mandatory in
most cars next year. However, it is important
to note that an estimated 30 percent, or fewer,
of those having belts actually wear them.?**47

A 1961 Swedish survey showed, for example,
that although 85 percent of all Swedish cars
manufactured at that time were equipped with
safety belts, two separate investigations showed
only one out of four (25%) motorists using them
by 1962.° There appears to have been no im-
provement in usage since then. In a recent series
of five surveys of seat belt usage made within
the past year by the Ford Motor Company
(1966), observers stationed on overpasses above
the traffic found that for 779 Detroit expressway
motorists utilization of the belt was similar in
both weekend and weekday rush hour traffic.
While 53 percent of the vehicles observed had
seat belts installed, at least one occupant was
using them in only 54 percent of these cars. In
other words, only one person in a car equipped
with belts was using them in only 28 percent of
the cases observed (233 of 779 cars). A smaller
survey also indicated that for one selected mo-
torist population, seat belts were not used (24%
at night, 16% at noon) as frequently for local
driving as for Detroit expressway driving.*’
Note also that in its Siath Annual Seat Belt
Installation and Use Survey (1966) the Auto
Industries Highway Safety Committee found “a
general downtrend over the years in percentage
of use, contrasted with an increase in installa-
tion.”*



ACKNOWLEDGMENT

The presentation of material in this paper has been possible only through
the generous efforts and assistance of a number of individuals interested in
impact protection and including scientific, engineering, and medical colleagues,
police, and accident survivors.

In particular, we wish to acknowledge the assistance of Robert A. Bieber,
California Highway Patrol, for alerting us to seat belt accidents involving
pregnant women in California during 1966-67; John N. Ice, Biomechanics
Department, Engineering Staff, Ford Motor Company, for his assistance
with the medical literature; Capt. Richard Sonntag, M.D., and Richard
Chandler, of the 6571st USAF Aeromedical Research Laboratory, Holloman
AFB, New Mexico; Col. G. Townley Price (USA Ret.) D.V.M., Federal
Aviation Administration, Civil Aeromedical Institute, Oklahoma City; and
Dr. Allan Katzberg, micro-anatomist, Southwest Foundation for Research
and Education, San Antonio, Texas, for pathological and necropsy support.

AUTHORS:

R. G. Snyder, Ph.D., Highway Safety Research Institute, Institute of
Science & Technology, University of Michigan, Ann Arbor, Michigan.

W. M. Crosby, M.D., Department, of Gynecology and Obstetrics, University
of Oklahoma Medical Center, Oklahoma City, Oklahoma.

C. C. Snow, Ph.D., Civil Aeromedical Institute, Federal Aviation Admin-
istration, Oklahoma City, Oklahoma.

J. W. Young, A.M., Civil Aeromedical Institute, Federal Aviation Ad-
ministration, Oklahoma City, Oklahoma.

P. Hanson, M.S., 6571st Aeromedical Research Laboratory, Holloman AFB,
New Mexico.

Qualified requesters may obtain Aviation Medical Reports from Defense Documentation
Center. The general public may purchase from Clearinghouse for Federal Scientifie and
Technical Information, U.S. Dept. of Commerce, Springfield, Va. 22151


the interacinar and intralobular hemorrhages
observed in the pancreas should merit further
study of the effect upon survivability.

Search of the literature has revealed descrip-
tions of pancreatic trauma related to dietary
excesses, direct trauma resulting from blows over
the left upper quadrant of the abdomen, surgical
trauma, and reflux from the intestine. However,
we have found no reports of pancreatic injury
associated with violent compression and/or dis-
placement of the viscera such as that found in
this series of experiments. Retroperitoneal and
intralobular hemorrhage was observed immedi-
ately after impact in gross necropsy, and upon
histological examination interacinal hemorrhage
was also found. Although it must remain spec-
ulative until further clinical study of survivors
is done, we feel that intra-abdominal forces were
sufficient not only to rupture the capillary bed
but also to break the more delicate radicles of
the intralobular ducts which are formed only by
the centro-acinous cells with the release and
activation of pancreatic enzymes.

While this continuing series of impact tests,
considering variables such as restraint system,
direction and magnitude of force, body orienta-
tion, time duration, seat pitch, and other factors,
may not appear extensive, it must be pointed out
that to our knowledge, these represent the first
experiments conducted utilizing living subjects,
involving the three-point harness and the preg-
nant female and fetus, and the first lateral tests
of the lap belt at levels above subjective human
tolerances.

B. Gross Biomechanical Considerations:
The kinematic action of the body during belted
impact has been well documented by analysis of
high-speed cinephotography during impacts of
anthropomorphic —dummies*?*551925198 and
many others. McHenry (1965) has attempted
to analyze the dynamics of the lap belt or com-
bination of lap belt and shoulder restraint
through a seven-degree-of-freedom nonlinear
mathematical model of a human body.* The
dynamics of belted, specially “flexed” human
cadavers have been studied by Patrick and
Daniel.** Researchers utilizing the Daisy Track
at Holloman Air Force Base, New Mexico, have
utilized high-speed photo analysis of both animal
and human subjects®*"%**°" as well as photo-
metric computer analysis of motion during
impact.**

1

Each of these techniques for understanding
the biomechanics of injury and restraint during
impact has shortcomings which persist in pre-
venting us from learning as much as we need to
know to design for optimum occupant safety.
Anthropomorphic dummies are most commonly
used for testing where human simulation is nec-
essary but where it is much too dangerous to use
human volunteers; however, dummies are also
the most misused and least understood devices
utilized. All too often the anthropomorphic
dummy, which can be an excellent engineering
tool for determining such things as amount of
force and duration of force, becomes to the engi-
neer an accurate human simulator, which it is
in only very limited ways. It is indeed a risky
business to attribute, as has been done, specific
trauma to a dummy impacted in a crash. Ac-
celerometers attached to the nonyielding steel
framework of the dummy cannot be quantified
to damage to soft tissue, organs, or to the cardio-
vascular, endocrine, or neurological systems.
What are the internal pressures, the distortion
of the heart and other organs? Thus an impact
quite tolerable by dummy standards may not be
for the actual human. Similarly, most dummies,
as actually used in tests today, are based upon
physical dimensions derived from a specific
young, male, physically select military popula-
tion, and do not necessarily represent the range
of automotive vehicle occupants in physical size
or attributes. Even the most valid attributes of
the anthropomorphic dummy, the range of joint
movement or centers of gravity, may be ques-
tioned since much of the basic data were derived
from only three elderly (67-71) male cadavers.
More recent data upon 14 cadavers ranging in
age from 21 to 67 years has not as yet been pub-
lished.*° The variation of tightness of joint
movement (force) does allow reproducible stand-
ardized testing, which is, of course, the function
of the dummy, but at the same time this may
not be accurate enough. In a recent study each
of 23 anthropomorphic dummies used in one or-
ganization’s test operations was carefully meas-
ured and examined for conformity to the manu-
facturer’s basic design specifications. It was
found that in dummies procured exactly the same
for the 50th percentile size, for example, body
weight varied by 12 pounds and total height by
2,6 inches.* Obviously some dummy users are
not aware of this quality control variable in their



have yet to document such a situation occurring
in actual automotive crashes.”

IV. Discussion

Review of the epidemiological and clinical
studies cited in this paper clearly shows that
seat belts do greatly assist the automotive occu-
pant in the prevention of more extensive or fatal
injuries in most impact situations as compared
to the nonbelted occupant. But these studies,
reinforced by experimental data, also indicate
that effectiveness is dependent upon a number
of environmental factors, and that while some
seat belt restraint systems offer measurably
greater protection to the individual than others,
even the “best” system can offer poor protection
under some circumstances.

There appears to be relatively universal agree-
ment among researchers as well as clinicians that
the major usefulness of any seat belt restraint
system is in the prevention of ejection from the
vehicle during an impact. Indeed, Campbell and
Kihlberg in a Cornell Aeronautical Laboratory
ACIR study conducted in California in 1963,
found no substantial benefits from 232 matched
pairs of accident occupants, half wearing belts,
and half not wearing belts, through preventing
or reducing contact, with interior vehicle surfaces,
beyond ejection control.?°

Other factors can influence injuries as well.
For some time, for example, there apparently
has been a fundamental disagreement between
American and European researchers concerning
use of the lap belt (as used extensively in the
U.S.) compared with the single diagonal only
system (as used more prominently in Europe)
and which probably is in 85% of Swedish cars.*

In the United States, the lap belt is the most
commonly used seat belt system, and has been
standard equipment for both front and rear seats
in all American automobiles since the 1966 models
were introduced. Attachment (anchorage, or
tie-down) is to the floor on both sides of the seat
normally allowing a belt angle of 40° to 60° to
the horizontal. Correctly mounted and worn, it
provides support of the body’s sturdiest frame-
work, the pelvic girdle. It has the disadvantage
of allowing the head and thorax to swing free
in a “jack-knife” motion during impact. The
diagonal (or “bandolier”) belt, on the other hand,
is anchored to the B-post pillar or above the
rear door, and extends across the shoulder and

14

chest on the outboard side, diagonally across the
flank on the opposite side, where it is anchored
to the floor. This provides diagonal vertical
support to the torso, from the hip on one side to
the shoulder of the opposite side. The major
disadvantage, however, is that with no lap belt
horizontal support across the anterior pelvic area,
there is swinging forward and rotating out of
the belt at impact (unless stopped by striking
the instrument panel or other part of the vehicle
itself).

In the smaller European car there is much less
distance between the occupant and any potential
environmental impact surfaces. In this situa-
tion, the lap belt, which allows upper torso flexion
forward during —Gx impact, is certainly not as
effective in preventing or reducing injury in im-
pact as is a system restraining the upper torso.
The use of a lap belt only, while generally pre-
venting ejection “can not provide adequate pro-
tection to a seated occupant since the upper body
components (e.g., head) are free to move during
abrupt decelerations and strike surrounding
structures.”°*

However, we must caution those advocating
the use of the single diagonal belt only (with
no lap belt) as an adequate seat belt system.
While the number of experimental tests that we
have run to date on primates is insufficient—as
presented in preliminary form in this paper—to
make valid conclusions, the results to date do
indicate strongly that this can be a highly dan-
gerous device. In some 47 experimental tests a
number of environmental variables have been
explored. In tests utilizing the same size primate
subject with identical deceleration patterns, di-
rection of force, body orientation, time duration
and rate of onset of impact, seat belt tension,
and seat configuration, by direct comparison even
the lap belt, purposely incorrectly placed loose
and high on the abdomen, resulted in less trauma
to the subject from impact alone than that oc-
curring with the diagonal belt alone. Our work
so far strongly supports the opinion of medical
consultants to Consumer’s Reports in a compari-
son of various seat belt systems, who warned
as early as 1962, “In a severe front-end crash,
CU’s tests indicated, this strap might cause criti-
cal injuries to internal organs (or the neck, when
the wearer slides down out of the belt). Even a
lap strap alone is preferable, since at least it puts