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"Low Speed Impacts: Does No Property Damage = No Injuries?"

Trial Lawyer Section of the Florida Bar
February 2000

Article Author: Paul E. Godlewski


Introduction

Lawyers representing injured victims of automobile collisions continued to encounter the use by the insurance industry and the defense bar in no fault and liability claims of "experts" to "prove" that the victim could not have been injured in the accident because the speed of the impact was "too low." According to these "experts," there is an absolute speed threshold below which, they claim, physical injuries never can occur. Although this proposition, on its face, is presumptuous, the plaintiff's lawyer cannot ignore it because this argument increasingly is advanced by the defense.

This article is intended to set out the basic scientific principles involved in this important issue and demonstrate the fallacy of the underlying premise — that all low speed crashes and victims are 100% identical in every respect and those crashes could not, medically and scientifically, under any circumstances, result in injury. Ultimately, this article will show that there is no credible research to support this proposition. In addition, in the event a judge mistakenly admits this "expert" testimony, this article will help show that this truly "junk science" can be rebutted.

Basic Terminology and Principles of Physics (Newton Revisited)

Any discussion regarding the physical forces involved in collision requires a brief review of some of the basic terminology and applicable laws of physics.1

· Delta v: Delta v is a change in velocity.

· Acceleration: A change in velocity over time.

· Delta t: Delta t is the duration of a collision.

· Inertia: As expressed in Newton's First Law of Motion, every body continues in its state of rest or of uniform motion in a straight line except insofar as it may be  compelled to change that state by the action of some outside force.

· Momentum: Motion energy of an object, or momentum, is equal to the mass of an object multiplied by its velocity. Momentum is also proportional to force — a larger momentum equals a larger force. In a collision, this momentum or energy is transmitted from one vehicle to the vehicle it hits.

· Conservation of momentum: Newton's Third Law of Motion states that the momentum in any collision must be conserved. In a collision between two cars, the momentum or energy that exists before a collision must exist after the collision. Energy does not disappear. This expression includes weight and speed of vehicles.

· Energy absorption: Energy absorption, known as the Coefficient of Restitution, is a recognized variable in the application of models of physics. The extent of energy absorption in a collision will vary with the external forces acting on the vehicle, such as road conditions (icy, wet, dry), tire condition and friction of the tires on the roadway, braking (anti-locks, condition of brakes), and vehicle deformation (dependent on the year, make, and model of the vehicle).

· G forces: A "g unit," as generally used by engineers, is the acceleration of gravity. As it is used in automotive safety analysis, it can be considered as either a force or an acceleration. Using the applicable equation, the force is equal to the multiples of acceleration times the weight.2
Impact Forces on the Human Body

In 1955, Severy3 conducted a study of rear-end crashes using anatomical dummies, human subjects, and high speed film. This and subsequent studies dispelled the belief that (contrary to what most accident victims still report) the first movement of the head and neck in a rear-end collision was forward, resulting in hyperflexion (forward motion of the head). Instead, the first movement in a rear-end impact is the torso moving forward as a result of the force through the frame and seat of the car.
The head and neck are left behind, resulting in hyperextension. The head and neck then go forward into flexion — all movements are involuntary, sometimes with the muscles tensed if the victim had a warning of impact. When the head and neck are in extension, the g forces pull the head down, further aggravating injury. Usually, the person does not remember hyperextension because it occurs so rapidly. Although injuries can occur in flexion or hyperflexion, studies show that most injuries in rear-end collisions occur in hyperextension.4

Although most experts should agree that even in low speed impacts there will be a difference in the acceleration of the torso, and the acceleration of the head, the defense and its experts claim that the change in velocity (or delta v) is so low that, even if the torso goes forward and the head follows, there is no hyperextension or hyperflexion.

Although some studies have found that low speed impacts do not always result in hyperextension, that fact, by itself, does not translate to "no injury." There is still a rapid change in velocity, and other factors, such as torque and compression, can act simultaneously to cause injury.5 In low speed collisions, there may not be a true whiplash phenomena. However, injury might be caused through a combination of vertical motion and horizontal motion not necessarily resulting in hyperextension.6

The key to understanding how a low speed can cause injury requires an analysis of the complex physical forces and human factors at work in every collision and the many variables (often difficult to quantify) that must be considered. One author summed it up well following his study:
Over all, the motion of human volunteer occupants even at very low severities are too complex for a simple correlation to exist between vehicle impact severity and single descriptors of occupant motion.7

It is well beyond the scope of this article to examine each variable in detail. However, it is important to be aware of them and the role they may play in causing injury. It is also important to be aware of how defense experts will attempt to focus on an applicable physics principle in isolation, without consideration of the many variables at work.

For example, defense experts often focus on g forces, which can be significant but are not the only factor. A study by Szabo8 shows that head g forces can reach up to 17 g in a 9 mph rear-end collision. The human head can weigh anywhere from 9 to 12 pounds. Using an average head weight of 10, the actual weight of the head in a 9 mph rear-end collision becomes 10 x 17 = 170 pounds, all within 60 milliseconds. This is equivalent to attempting to support 170 pounds with your neck alone. Applying this model, however, is not so simple, because the forces in a rear-end collision are dynamic, not sterile or static. Both the head and the torso have inertia. It is the muscles of the neck, structures of the spine,9 and the brain10 that are susceptible to injury when these changes are rapid, even in low speed collisions.11

Engineering experts who claim that there can be no injury in low speed crashes apply calculations that involved a sterile application of absolute g forces. These are not severe and often are argued as similar or less than bumper cars at an amusement park. However, these calculations do not include the difference in masses and weight involved in two colliding vehicles nor do they consider the difference in the movement of the head and neck as separate from the shoulders and torso. These calculations also ignore compression forces and the phenomena of ramping, discussed below.

When reviewing the voluminous engineering, scientific, and medical data on the subject of low speed collisions, it becomes obvious that most researchers and authors are attempting to apply an objective formula at the outset of their studies to arrive at objective data at the end for use as a constant in the future. Yet, the more one reads, the more one observation becomes clear — no one can harness all the other variables.12 Consequently, each study inevitably relies on assumptions — some strong, others weak. These assumptions may be well stated or subtle, but they are key to the strength or weakness of the author's conclusions and may bear heavily on the purpose for which the article is being used in your case. A review of some of the many variables at work in a collision helps demonstrate this point.

Human tolerance to injury: All of the studies of collision forces using both volunteer subjects or anatomical dummies occur in a controlled environment. Seat backs are upright. Head rests are in place and, in the case of live subjects, they are prepared for impact. In the real world, there are wide variables in human tolerance to avoid or sustain injuries in low speed impacts. Age, sex, general health conditions, physical size, and skeletal development affect impact tolerance of various individuals.13 Schutt and Dohan reported that women were 4.8 times more likely to receive a whiplash injury than males in urban populations and 1.7 times more likely in rural areas.14 Snyder15 used comprehensive anthropometric data to study the effects of neck size, length, strength, and range of motion. Males have larger, stronger necks with less range of motion than females. Snyder's data demonstrates that range of motion decreases with age. Yet, no formula or calculation expresses these variables in absolute constant terms, and they usually are ignored in low speed impacts.

Head restraints: Although helpful in some cases, head restraints do not necessarily avoid or entirely reduce injury.16 To be effective, the back of the head and the head restraint should be no more than a few inches (1"-4" maximum) apart.17 Any greater distance allows for hyperextension.18 Also, in those studies that show that low speed impacts may not necessarily result in hyperextension, head restraints are of no value when the rapid changes in velocity occur, resulting in horizontal and vertical motions that still can cause injury.19

An important reason for the limited effectiveness of head restraints is that people do not always sit perfectly when hit, with their backs and shoulders squarely against the seat. If a person is reaching for the radio, turning his or her head in conversation, or looking for crossing traffic, this may cause the head to travel a great distance rapidly and exacerbate the effects of a low speed crash.20
Besides proper head restraint adjustment, seat adjustment is also a factor. If seats are adjusted so that they lean back or forward, the head may freely extend without ever touching the head restraint. Studies also have shown that the neck and spine could be compressed by the top of the head hitting the restraint.21

Even with the head restraint adjusted properly (right behind the center of gravity of the head), if an occupant "ramps" over the seat, the head restraint is useless and even may enhance injury.22

Ramping: Ramping is the motion of the occupant up the back of the seat, sometimes only a few inches,23 and, in severe cases, significant enough to go into the back seat.24 Even seat-belted occupants can ramp up the back of the seat, and the height and angle of the headrest can severely exacerbate injury, even in a low speed accident. Studies have shown that ramping can cause excessive bending and tension as well as compression forces downward on the neck and spine as the body moves up and back against the seat back and head rest. This also involves the application of vertical and horizontal forces that can produce injury. Seat belts can, but do not always, reduce ramping, depending on the angle of the seat and the height and weight of the occupant at the time of impact. Studies show that neck injury frequency also increases with occupant height.25

Seat characteristics: This variable changes from automobile to automobile, depending on the year, make, and model. The concept of differential rebound was introduced by States and his colleagues.26 They hypothesized that some injuries were explained by the existence of different spring rate characteristics in the main section of the seat back and the head restraint. As the occupant compressed the seat cushion in the first part of the impact sequence, energy was stored by the seat and head restraint. Head restraints usually are covered with slow recovery foam, whereas the spring character of the seat back returns energy much faster. The result was thought to be that the torso rebounded much faster off the seat than did the head from the head restraint, with the consequence that hyperextension of the neck was produced during this rebound phase (a demonstration of the different rate of acceleration of the torso and the head). With the differential rebound characteristics of a seat, depending on its spring tension and coefficient of restitution, the delta v forces transmitted in a rear-end collision could increase substantially. In a low speed impact, a seat back that has a firm bounce will have a multiple of the delta v transmitted in the initial impact.27

Additional variables for any given seat design should include an examination of the extent of occupant-induced seat deformation as the result of rear-end collision forces. One study suggested28 that the extent of occupant-induced seat deformation as the result of rear-end collision forces is directly proportional to the delta v of the struck vehicle as well as the weight and posture of the occupant and the weight and strength of the seat. Force must be applied through the seat to accelerate the occupant during the collision phase. The seat back rest yields rearward and other seat components deform when the resulting forces exceed the strength of the seat structure. Seat backs can actually twist and rotate during rear-end collisions, particularly if the occupant is heavy set, and more particularly if the occupant is heavy set and tall. This phenomenon, when evaluated in the context of the ramping mechanism, causes the body to go up while the head remains in a fixed position. In addition to the compression and vertical and horizontal forces involved, the head can rotate sharply backwards or forwards in hyperextension or hyperflexion without dramatic movements rearward or forward.29

Clothing: The type of clothing a person is wearing can have a dramatic effect on ramp, torque, and compressive force. Research by Carr, Posey, and Wilson found that a nylon jacket combined with a leather seat will have a friction coefficient 1.6 times higher than a tweed jacket on a heavy cloth seat.30

Angle of collision: Angular collisions rarely are studied because of the risk to the test subjects and because of the nonuniform application of g forces in a three-dimensional perspective. One study found that, in collisions that were off center by just 15%, the seat back would twist with the off center force.31 This twisting resulted in greater total movement of the head because the head would miss the restraint entirely. Combined with the concept of differential rebound discussed above, an angular impact most likely would have twisting and rotational forces in addition to the vertical and horizontal forces in injury-producing scenarios. Angular impacts also have more potential for causing an occupant to hit his or her head on the window or posts or move in the direction in which there is no head restraint.

Body size and position: How a person is sitting, the extent of muscle mass or lack thereof, whether the person is are small boned or large structured all would have an influence on whether injury is sustained in low impact scenarios.32

Bumper to bumper and bum-per override: Energy-absorbing bumpers found on newer model cars are intended to decrease damage to autos in low impact collisions and also help reduce neck and back injuries. Energy-absorbing bumpers are designed to achieve this goal by increasing delta t, or the duration of the collision. For example, an airplane lands at high speeds but over a long duration, thus increasing delta t and decreasing the g forces.33

However, the mere existence of energy-absorbing bumpers does not answer the question of whether an impact was low speed — in fact, they could belie evidence of a significant impact.34 Look for evidence of damage to the bumper mounts or bumper shock absorbers. If the energy-absorbing bumpers are fully suppressed flush to the bumper mounts, the advantages of the delta t or increasing the duration of the collision are dampened.

Prepared for impact: If an accident victim is ready for the impact and braces, there may be less torque, particularly in the low speed impact.35

Susceptibility to injury; aggravation of preexisting conditions: Although it may seem trite to state the obvious, most doctors usually predict that, once a person is injured, the person is more susceptible to reinjury in a subsequent but less severe accident.36 Age studies also show37 that the elderly tend to be injured more frequently than younger people in lower speed impacts.

Occupant position at time of impact: Although hyperextension usually occurs before hyperflexion, in some cases the posture of the occupant at the time of impact (such as leaning forward or stooping the head)38 actually causes flexion to occur first. This would subject the occupant to more excessive vertical and compression forces.39

Roadway conditions: The condition of the roadway is an important variable because a rear-end collision on ice actually may increase the delta v forces, because there is less resistance of the tires on the roadway. It also may cause angular motion and spinning, which can lead to rotational forces in addition to the horizontal and vertical forces.40

Multiple car collisions — the middle vehicle: An enhancing risk-producing mechanism is the additional risk to flexion injuries when struck from the rear and forced into a car in front. Usually flexion occurs after the rear-end collision, and, if the forward acceleration is still in progress at the time of the second impact, flexion can be exacerbated into hyperflexion in low speed crashes.41

Size and mass of vehicles: Frequently overlooked in low speed collisions is the relative difference even among very similar vehicles and the large mass involved in the collision.42 Cargo content is also an important element: Was the pickup truck empty or full of landscape rock?

Scientific Literature

There is no lack of research and data banks from which to draw specific information regarding the collision speed and injuries. Case studies on neck and whiplash injury can be traced to Dr. Crowe, a surgeon who presented eight cases of neck injuries from traffic accidents in 1928.43 This concept was looked at more closely by the United States Navy after observing the phenomenon of neck injuries in pilots who were injured when catapulted from aircraft carriers. This research led to the finding that a high seat supporting the head, upper back, and neck during acceleration prevented hyperextension, which was identified as the main cause of those injuries.44

Although books and articles can be found on a national and international level, probably the single largest data-base is with the Society of Automotive Engineers (international web site is www.sae.org).

Since 1956, the Society of Automotive Engineers (SAE) has sponsored the Stapp Car Crash Conferences, which have been hosted by various colleges, universities, and technical institutions. These conferences publish studies that are cleared through the SAE advisory committee.

The focus of these research articles is on automotive design and occupant safety. Whether the research was generated and presented under the auspices of the SAE or otherwise, methodologies and technology have become more sophisticated over time. The earlier studies used primarily sled tests and impact barriers, which do not necessarily reflect the dynamics involved between two colliding vehicles on a roadway. The anatomical models first used were primarily male and not as sophisticated as the current models, which more closely match body mass, soft tissue, and bone structure. Cadavers sometimes were used; in earlier studies, rarely were human volunteers used.

More recent studies now include vehicle-to-vehicle crashes, current automotive, seatbelt, and seat designs, and more representative anatomical models of women and children. However, these studies always seem to rely on a compromise of an "average" person, and therein lies some major differences when applied to real world crash facts.45

The current studies also focus on low speed crashes in which there is little property damage to cars. High speed, slow motion videography demonstrates the motion of dummies, cadavers, and live subjects in low speed impacts. These studies show the numerous variables discussed above, which strongly suggest that there is no constant threshold below which injury does not occur and above which injury does occur. We are all familiar with the scenario in which a person remarkably escapes injuries in a severe crash, even though another occupant of the same vehicle sustains serious injuries. There are infinite variables at both ends of the spectrum that can only be looked at on a case-by-case basis.

It must be kept in mind that the engineering research discussed in this article occurs in a controlled environment at low speeds with live subjects who are healthy and strong. For good reason, these studies do not subject live volunteers to high speed impacts or attempt to intentionally induce injury by having occupants sit improperly or by recruiting elderly or previously injured persons to participate as test volunteers. Even under strictly controlled conditions at low speeds when every precaution had been taken to avoid injury, some research volunteers have reported post-collision symptoms, including neck, back, and headache pain without hyperextension or hyperflexion.46

Plaintiff's counsel should direct the focus of the inquiry in low speed scenarios to the nature and extent of injury when clients report post-collision symptoms. This is especially important now because some insurers deny no-fault benefits right from the very beginning for emergency room care by disregarding the health care providers' documentation of injury and rely instead on an engineering report stating that there is no injury in a particular low speed crash. Whether in the context of a no-fault or liability claim, this approach raises serious questions when applying the very basic rules of evidence regarding adequate foundation for expert opinion on the causation of injuries. Advocacy on behalf of injured accident victims requires objections to this testimony, proper preparation for cross-examination, and motions in limine at both the no-fault arbitration level and before trial, so that these distorted opinions do not become part of the weight of the evidence to be considered by the fact finder.

Beyond Physics (The Jury Doesn't Know Newton, But Has Met Your Client)

In proving an injury from a low speed collision when the defense expert on "speed threshold of injury" is allowed to testify, never let this distraction cause you to overlook the usual evidence of injury, such as post-accident medical records, factual witnesses, and other occupants' complaints of pain, even minor, in all cars involved in the crash. Even when x-rays taken were "negative," a qualified radiologist or professional experienced in treating neck injuries may see evidence of loss of lordotic curve. How soon after the accident were the x-rays taken? Follow-up x-rays taken 24-48 hours after the accident may show evidence of an increase in the loss of lordotic curve or a new finding of a slight loss of the lordotic curve not present at the time of the first x-rays. Finally, it is critical to remember perhaps the most important of Newton's Laws: Energy does not disappear — it is transmitted to the impacted vehicle and, hence, to your client.

Paul Godlweski of Schwebel, Goetz & Sieben, P.A. is certified by the National Board of Trial Advocacy and the Minnesota State Bar Association as a civil trial specialist. This article is edited and reprinted with permission from Trial Talk (1/98).

1 Blatt, F.J. Principles of Physics, Allyn & Bacon, 1986; Handbook of Chemistry and Physics 1967, The Chemical Rubber Company.

2 Patrick. L.M., Human Tolerance to Impact and Its Application to Safety Designs, Biomechanics and Its Application to Automotive Design, 1973 1-15.

3 Severy, D.M., Mathewson, J.H. and Bechtol, C.O., Controlled Automobile Rear-end Collisions, an Investigation of Related Engineering and Medical Phenomena, Canadian Services Medical Journal, 1955, November: 727-759.

4 Society of Automotive Engineers, Human Tolerance to Impact Conditions as Related to Motor Vehicle Design, SAW J885, April, 1980, Handbook Supplement HS 885, April, 1980; States; J.D., Soft Tissue Injuries of the Neck, 1979, SAE 790135.

5 Ewing, C.L., Thomas, D.J.., Lustick, I., et al, The Effect of the Initial Position of the Head and Neck on the Dynamic Response of the Human Head and Neck to Gx impact Acceleration, 19th Stapp Car Crash Conference, 1975, SAE: 751157.

6 Benson, B.R., Smith, G.C., Kent, R.W. and Monson, C.R., Effect of Seat Stiffness in Out-of-Position Occupant Response in Rear-end Collisions,40th Stapp Car Crash Conference, 1996, SAE 962434; McConnell, W.E., Howard, R.P., Guzman, H.M., et al., Analysis of Human Test Subject Kinematic Responses to Low Velocity Real End Impacts, 1993 SAE 930889; McConnell, W.E., Howard, R.P., Van Popel, I., et al., Human Head and Neck Kinematics after Low Velocity Rear-end Impacts - understanding Whiplash, 39th Stapp Car Crash Conference, 1995, SAE 952724; Pintar, F.A., Myklebust, J.B., Yoganandan N., et al., Biomechanics of Human Spinal Ligaments, Mechanisms of Head and Spine Trauma, Sances, A., Thomas, D.J., Ewing, C.L., et al., Ed., pp. 505-527; Szabo, T.J. and Welcher, J.B., Human Subject Kinematics and Electromyographic Activity During Low Speed Rear Impacts, 40th Stapp Car Crash Conference, 1996, SAE 962432.

7 Bailey, M., Assessment of Impact Severity in Minor Motor Vehicle Collisions, Journal of Musculoskeletal Pain, 1996, 4(4):21-38.

8 Szabo, T.J. and Welcher, J.B., Human Subject Kinematics and Electromyographic Activity During Low Speed Rear Impacts, 40th Stapp Car Crash Conference, 1996, SAE 962432.

9 Society of Automotive Engineers, The Human Neck — Anatomy, Injury Mechanisms and Biomechanics, 1979, SP - 438, SAE - SP - 79/438.

10 Burke, J.P., Orton, H.P., West, J., et al., Whiplash and Its Effect on the Visual System, Graefe's Archive on Ophthalmology, 1992, 230:335-339; Ommaya, A.K. and Hirsch, A.E., Tolerances for Cerebral Concussion from Head Impact and Whiplash in Primates, Journal of Biomechanics, 1971, 4:13-21; Ommaya, A.K. and Yarnel, P., Subdural Hematoma after Whiplash Injury, The Lancet, 1969, 2:237-239; Ommaya, A.K., The Neck: Classification, Physiopathology and Clinical Outcome of Injuries to the Neck in Motor Vehicle Accidents, The Biomechanics of Impact Trauma, Aldman, B. and Chapon, A., Ed., Elsevier Science Publishers, 1984, 127-138; Otte, A., Ettlin, T., Fierz, L. and Mueller-Brand, J., Parieto-occiptal Hypoperfusion in Late Whiplash Syndrome: First Quantitative Spet Study Using Technetium-99m Biciate (ECD), European Journal of Nuclear Medicine, 1996, 23(1):72-74.

11 Roberts, E.L. and Compton, C.P., The Relationship Between Delta v and Injury, 37th Stapp Car Crash Conference, 1993, SAE 933111.

12 Patrick, L.M., Human Tolerance to Impact and Its Application to Safety Design, Biomechanics and Its Applicatioin to Automotive Design, 1973 I-15.

13 Patrick, L.M., Human Tolerance to Impact and Its Application to Safety Design, Biomechanics and Its Applicatioin to Automotive Design, 1973 I-15.

14 Friedmann, L.W., Marin, E.L., and Padula, P.A., Biomechanics of Cervical Trauma, in Painful Cervical Trauma: Diagnosis and Rehabilitative Treatment of Neuromuscular Injuries, Tollision, C.D. and Satterthwaite, J.R., Ed., 1992, 10-19; Evans, R.W., Some Observations on Whiplash Injuries, Neurol. Clin., 1992, 10:975-997.

15 Snyder, R.G., Chaffin, D.B. and Foust, D.R., Bioengineering Studies of Basic Physical Measurements Related to Susceptibility to Cervical Hyperextension Hyper Flexion Injury, HSRI Ann Arbor, Univ. of Mich., 1975; Snyder, R.G., et al., Basic Biomechanical Properties of the Neck Related to Lateral Hyperflexion Injury. HSRI Ann Arbor, Univ. of Mich. 1975.

16 International Research Council on Biokinetics of Impacts, 1985 International
IRCOBI/AAAM Conference on Biomechanics of Impacts, Proceedings (Sweden).

17 Status Report, Special Issue: Whiplash Injuries, Insurance Institute for Highway Safety, September 16, 1995.

18 Sturzenegger, M., DiStefano, G., et al., Presenting Symptoms and Signs after Whiplash Injury: The Influence of Accident Mechanisms, Neurology, 1994, April: 688-693.

19 McConnell, W.E., Howard, R.P., Guzman, H.M., et al., Analysis of Human Test Subject Kinematic Responses to Low Velocity Real End Impacts, 1993 SAE 930889; McConnell, W.E., Howard, R.P., Van Popel, I., et al., Human Head and Neck Kinematics after Low Velocity Rear-end Impacts — Understanding Whiplash, 39th Stapp Car Crash Conference, 1995, SAE 952724.

20 Matsushita, T., Sato, T.B., Hirabayaski, K., et al., X-ray Study of the Human Neck Motion Due to Head Inertial Loading, 38th Stapp Car Crash Conference, 1994, SAE 942208; Sturzenegger, M., DiStefano, G., et al., Presenting Symptoms and Signs after Whiplash Injury: The Influence of Accident Mechanisms, Neurology, 1994, April: 688-693.

21 International Research Council on Biokinetics of Impacts, 1985 International IRCOBI/AAAM Conference on Biomechanics of Impacts, Proceedings (Sweden).

22 Ono, K. and Kanno, M., Influences of the Physical Parameters on the Risk to Neck Injuries in Low Impact Speed Rear-end Collisions, Accident Analysis and Prevention, 1996, 28(4):493-499.

23 McConnell, W.E., Howard, R.P., Guzman, H.M., et al., Analysis of Human Test Subject Kinematic Responses to Low Velocity Real End Impacts, 1993 SAE 930889; McConnell, W.E., Howard, R.P., Van Popel, I., et al., Human Head and Neck Kinematics after Low Velocity Rear-end Impacts — Understanding Whiplash, 39th Stapp Car Crash Conference, 1995, SAE 952724.

24 International Research Council on Biokinetics of Impacts, 1985 International IRCOBI/AAAM Conference on Biomechanics of Impacts, Proceedings (Sweden).

25 Warner, C.Y., Strother, C.E., James, M.B. and Decker, R.L., Occupant Protection in Rear-end Collisions: II. The Role of Seat Back Deformation in Injury Reduction, 35th Stapp Car Crash Conference, 1991, SAE 912914.

26 States, J.D., Soft Tissue Injuries of the Neck, 1979, SAE 790135.

27 Kornhauser, M., Delta-v Thresholds for Cervical Spine Injury, 1996, SAE 960093; Svenson, M.Y., Lovsund, P., Haland, Y. and Larson, S., The Influence of Seat-Back and Head-Restraint Properties on the Head-Neck Motion During Rear-Impact, Accident Analysis and Prevention, 1996, 29(2):221-227;Svenson, M.Y., and Lovsund, P., Rear-End Collisions: A Study of the Influence of Backrest Properties on Head-Neck Motion Using a New Dummy Neck, 1993, SAE 930343.

28 Severy, D.M., Blaisdeil, D. and Horn, L.S., Motorist Head and Body Impact Analysis, Methodologies and Reconstruction, SAE 850097, Mar. 1985.

29 McConnell, W.E., Howard, R.P., Guzman, H.M., et al., Analysis of Human Test Subject Kinematic Responses to Low Velocity Real End Impacts, 1993 SAE 930889; McConnell, W.E., Howard, R.P., Van Popel, I., et al., Human Head and Neck Kinematics after Low Velocity Rear-End Impacts — Understanding Whiplash, 39th Stapp Car Crash Conference, 1995, SAE 952724.

30 Carr, W.W., Posey, J.E., Tincher, W.C., Frictional Characteristics Of Apparel Fabrics, Textile Research Journal, 1988, March:129; Posey, J.E., Measurement of Frictional Characteristics of Fabrics, Georgia Institute of Technology, March 1984; Wilson, D., A Study of Fabric-On-Fabric Dynamic Friction, Journal of the Textile Institute Transactions, 1963, April: T143.

31 Viano, D.C., Restraint of a Belted or Unbelted Occupant by the Seat in Rear-end Impacts, 36th Stapp Car Crash Conference, 1992, SAE 922522.

32 Ommaya, A.K. and Hirsch, A.E., Tolerances for Cerebral Concussion from Head Impact and Whiplash in Primates, Journal of Biomechanics, 1971, 4:13-21; Patrick, L.M., Human Tolerance to Impact and Its Application to Safety Design, Biomechanics and Its Application to Automotive Design, 1973 I-15.

33 Patrick, L.M., Human Tolerance to Impact and Its Application to Safety Design, Biomechanics and Its Applicatioin to Automotive Design, 1973 I-15.

34 Status Report, Special Issue: Whiplash Injuries, Insurance Institute for Highway Safety, September 16, 1995; Szabo, T.J. and Welcher, J.B., Dynamics of Love Speed Crash Tests with Energy Absorbing Bumpers, 1992, SAE 921573.

35 Sturzenegger, M., DiStefano, G., et al., Presenting Symptoms and Signs after Whiplash Injury: The Influence of Accident Mechanisms, Neurology, 1994, April: 688-693.

36 Friedmann, L.W., Marin, E.L., and Padula, P.A., Biomechanics of Cervical Trauma, in Painful Cervical Trauma: Diagnosis and Rehabilitative Treatment of Neuromuscular Injuries, Tollision, C.D. and Satterthwaite, J.R., Ed., 1992, 10-19; Radanov, B.P. and Sturzenegger, J., The Effect of Accident Mechanisms and Initial Findings on the Long-Term Outcome of Whiplash Injury, Journal of Musculoskeletal Pain, 1996, 4(4):47-59.

37 Roberts, E.L. and Compton, C.P., The Relationship Between Delta V and Injury, 37th Stapp Car Crash Conference, 1993, SAE 933111.

38 Radanov, B.P. and Sturzenegger, J., The Effect of Accident Mechanisms and Initial Findings on the Long-Term Outcome of Whiplash Injury, Journal of Musculoskeletal Pain, 1996, 4(4):47-59.

39 Matsushita, T., Sato, T.B., Hirabayaski, K., et al., X-ray Study of the Human Neck Motion Due to Head Inertial Loading, 38th Stapp Car Crash Conference, 1994, SAE 942208; Sturzenegger, M., DiStefano, G., et al., Presenting Symptoms and Signs after Whiplash Injury: The Influence of Accident Mechanisms, Neurology, 1994, April: 688-693; Walmsley, R.P., Kimber, P. and Culham, E., The Effect of Initial Head Position on Active Cervical Axial Rotation Range of Motion in Two Age Populations, Spine, 1996, 21(21):2435-2442.

40 Melton, M., The Guide to Low Velocity Whiplash Biomechanics, Body-Mind Publications, 1997.

41 Melton, M., The Guide to Low Velocity Whiplash Biomechanics, Body-Mind Publications, 1997; States, J.D., Balcerak, J.C., Williams, J.S., et al., Injury Frequency and Head Restraint Effectiveness in Rear-End Impact Accidents, 16th Stapp Car Crash Conference, 1972, SAE 720967.

42 States, J.D., Balcerak, J.C., Williams, J.S., et al., Injury Frequency and Head Restraint Effectiveness in Rear-End Impact Accidents, 16th Stapp Car Crash Conference, 1972, SAE 720967.

43 States, J.D., Soft Tissue Injuries of the Neck, 1979, SAE 790135.

44 Melton, M., The Guide to Low Velocity Whiplash Biomechanics, Body-Mind Publications, 1997.

45 McConnell, W.E., Howard, R.P., Guzman, H.M., et al., Analysis of Human Test Subject Kinematic Responses to Low Velocity Real End Impacts, 1993 SAE 930889; McConnell, W.E., Howard, R.P., Van Popel, I., et al., Human Head and Neck Kinematics after Low Velocity Rear-End Impacts — Understanding Whiplash, 39th Stapp Car Crash Conference, 1995, SAE 952724.

46 McConnell, W.E., Howard, R.P., Guzman, H.M., et al., Analysis of Human Test Subject Kinematic Responses to Low Velocity Real End Impacts, 1993 SAE 930889;McConnell, W.E., Howard, R.P., Van Popel, I., et al., Human Head and Neck Kinematics after Low Velocity Rear-End Impacts — Understanding Whiplash, 39th Stapp Car Crash Conference, 1995, SAE 952724.

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