By
Raymond Paul Johnson
and
Mark Pozzi
2121 Rosecrans Avenue, Suite 3400
South Bay Los Angeles
Manhattan Beach, CA 90245
I.
INTRODUCTION
Due to persistent efforts by safety engineers, plaintiff lawyers and consumer advocates over the last forty (40) years, we are all safer on American highways. Today we enjoy the safety of padded interiors; front and side airbags; pretensioner devices on seatbelts (that deploy to keep occupants tightly belted in some frontal crashes); and frontal crush zones that save thousands of lives each year. But the work is not over.
Safety deficiencies still exist such as inadequate roof strength; the absence of effective rear crush zones; inherently unstable vehicles; exploding fuel systems; unreliable seatbelts and airbags, and other deadly defects. But perhaps the most egregious lack of safety with today’s vehicles are the dangerously weak seats and seatbacks that continue to fail during otherwise survivable rear collisions, killing and maiming Americans each year.
Basic engineering tells us that occupants within a vehicle generally move toward the impact during crashes. In a frontal impact, the occupants move forward relative to the vehicle as it is rapidly slowing. Therefore, they load into the seat belts, airbags, collapsible steering columns and padded dash structures provided in modern vehicles. In a rear-end collision, however, occupants of the struck vehicle move rearward. The primary vehicle structures that provide occupant protection in these rear impacts are the seats. This is elementary, yet people are killed, paralyzed and brain-damaged each year because most seatbacks are not strong enough to absorb foreseeable impact loads from the occupant within the seat.
What we are talking about are seatbacks that collapse rearward causing seatbelts to become loose around the seat occupants, and ejecting them rearward into the back of the vehicle during rear collisions.1 This leads to injury to front and rear seat-occupants, as well as loss of control that can cause other collisions or rollovers. Once an occupant is thrown out of position due to seat collapse, the seat belts and airbags that once were positioned to protect them, can now be instruments of enhanced injury.
These hazards are recognized by auto manufacturers and even described in vehicle owner’s manuals which instruct occupants never to recline or adjust seats while the vehicle is in motion, and that seatbelts and airbags can become less effective as a result. Unfortunately, most seats are so weak that these hazards exist, even if vehicle occupants follow these instructions to the letter.
Why and how people are injured or killed by weak seats are discussed below, as well as the inadequate safety standards involved. In addition, the telltale physical evidence showing how and why vehicle occupants are injured due to collapsing seatbacks is explored to assist you in better understanding these tragic cases. Finally, the authors review typical defenses posed by defendant manufacturers in these cases, and their efficacy.
II. HOW AND WHY WEAK SEATBACKS RESULT IN INJURIES AND DEATH
The deadly risks to both front and rear seat-occupants from seat failures are numerous and deplorable, yet these dangers continue to be largely overlooked by most vehicle manufacturers and safety agencies. The resulting injuries can be divided into two (2) categories: injuries and death to (1) front-seat occupants; and (2) vehicle occupants (including children) in the rear seats.
A. The Dangers to Front-Seat Occupants
When seatbacks collapse, front-seat occupants are ejected rearward out of their seatbelts, and can and do suffer head trauma, neck injury, or spinal cord damage from striking the rear seats and other areas in the back of the vehicles. Both authors have been involved with cases that have included skull fracture, permanent brain injury, paraplegia or quadriplegia.
In fact, during rear collisions, when the front-seat occupant’s head strikes rigid or hard surfaces at the rear of the vehicle, their head stops relatively quickly. Such rapid, aggressive stopping against rigid objects often results in severe brain damage. This is particularly true when the head strikes the metal areas around rear windows, the vertical members that support the roof (called pillars), or other improperly padded surfaces in the rear of the vehicle. Such injuries can be combined with neck trauma if there is sufficient compression, flexion, extension or rotation of the neck as a result of the rear impact. In other instances, the front-seat occupants can be partially or fully ejected out of the rear or side windows and slammed into the road or other vehicles.
Once the occupant is ejected rearward because of the weak seatback, their head can also strike the padded rear seat, which can bend around the head like a “baseball mitt” catching a round baseball. In such instances, the head stops relatively slowly but the body continues to load the neck, often in compression. If enough energy remains and the body’s tolerance to spinal loading is exceeded, there is a likelihood of severe neck dislocation and/or fracture. The authors have each investigated cases of quadriplegia where there is not a mark on the person and no loss of consciousness during the rear collision. Yet, the victims were found lying on the backseat with a neck fracture, unable to move.
This tragic injury mechanism relates to rear-impact tests in earlier literature where dummies were instrumented with head and chest impact sensors, but without load cells in the neck. (See National Highway Traffic Safety Administration (NHTSA) New Car Assessment Program (NCAP) Testing – 1979 to 1981). In most of those tests, injury levels for the head proved quite low due to the deformability of the rear seats. In many of the test results however, although the neck was not instrumented and no quantitative measurements of neck loading was taken, a careful look at the head and chest data revealed what actually happened. The data showed that after striking rear interior vehicle structures, the head stopped moving for several milliseconds before the chest stopped moving. This clearly evidenced the continued loading of the neck, and the potential for severe neck injury.
Each author has also investigated other cases where the head stopped and the body loaded up the neck in either flexion or extension, and sometimes compression. The unique etiology of the neck injury can evidence the direction of loading, especially if side facets are locked or spinous processes are fractured. One of the most injurious mechanisms is rotation, where the head stops, the body twists, and the neck is loaded.
Generally, compressive neck injury tolerances range from a low of 700 pounds for adult females to about 1,000 pounds for adult males. This is for neck vertebrae (C1 to C6). Compressive thoracic spinal injury tolerance (for the chest area) ranges from about 1,000 to 1,300 pounds. This is for vertebrae T1 to T12, which corresponds to your first through twelfth ribs. If however there is localized flexion, extension, or shear loads placed on the thoracic spine, this loading tolerance will drop. Unfortunately, the weaker areas of the spine (nearest the head) are closer to the impact in seat-collapse cases and are subjected to the greater likelihood of loading. For all practical purposes, this is similar to a diving injury, except that the dive is rearward into the back seat instead of downward into a pool.
Spinal injuries in such situations liken to the old adage that “a chain is only as strong as its weakest link.” Generally speaking, if the head is loaded in a seat-failure situation, the cervical vertebrae are most likely to fail, and can result in quadriplegia. In some instances, a basal skull fracture or ring fracture can occur in conjunction with the neck injury.
If the shoulders are loaded, however, the thoracic vertebrae are more likely to fail. This is because, if the head “misses” the rear seat or another object, the load is applied further down the spine, and paraplegia can be the result. The typical situation occurs when the rearward ejected occupant’s head bypasses the rear seat and the bottom of the neck and top of the shoulders are loaded beyond tolerance.
The authors have also each investigated instances where a front-seat occupant in a sports utility vehicle (SUV), extended cab pick-up, van or hatchback-type vehicle was ejected rearward head-first, and their spine contacted the narrow, unpadded top of a rear seatback or the edge of a side window or hatchback opening, which are all relatively narrow, force-concentrating structures. Severe head injury and/or paralysis was the result. And then other front-seat occupants have been ejected rearward through side windows or rear windows (called rearlights) or even hatchback windows. These rearward-ejected occupants have struck road surfaces, other striking vehicles, the edges of guardrails, power poles, guide wires, trees and other objects outside the vehicle. Death, paralysis and/or permanent brain injury can result.
B. The Dangers to Rear Occupants
Collapsing front seatbacks create other dangers, including the very real risks of severe or fatal injury to rear-seat occupants, often children. In such cases, the rearward ejected front-seat occupant acts like a battering ram against the head and chest of children and adults in the back seats. By comparison, intentional “head butting” is illegal in boxing matches due to the high likelihood of injury to the person being struck in the head. Yet, the available energy in a voluntary head butting movement is relatively minor compared to the energy levels typically affecting occupants in vehicle collisions.
For example, it is readily foreseeable that a 95-percentile male weighing about 220 pounds can easily generate 3,000 pounds of force when striking the rear seat or rear occupant in a head-first manner. This is not only triple the amount of force necessary to break one’s neck, it is also more than sufficient to kill the rear-seat occupant.
This danger that weak front seats pose to rear-seat occupants is particularly egregious today because airbags were noted in the 1990's to be killing and maiming short adults and children. As a consequence, the automotive industry and the National Highway Traffic Safety Administration (NHTSA) advised parents to put children in the rear seat to avoid airbag hazards. As a result, today, children are often the victims of collapsing front seats.
III.
OTHER DANGERS CAUSED BY WEAK SEATS
Rear-seat occupants can also be entrapped by failed front seats that collapse onto their legs. The authors have each seen instances where rear-seated children and adults have burned to death in rear impacts simply because they could not escape from the vehicle when the front seats collapsed onto them. This is especially dangerous with two-door vehicles, and in vans and SUVs with multiple rows of rear seats, where the rear-seat occupants became trapped.
In fact, it can be virtually impossible to exit rear-seat areas in some SUVs and vans if the forward seats have collapsed, unless one has the time, and is able to crawl up and over the seats. The likelihood of doing that however is far less if one’s legs have already been injured or entrapped by the collapsing seats.
Rear-seat occupants, both children and adults, have been severely injured by rearward-ejected front-seat occupants and collapsing front seats. This has caused face and head trauma, including skull fractures and severe brain injury to rear-seat occupants. In addition, severe neck and chest injuries such as ruptured hearts, torn aortas, and punctured lungs (due to broken ribs) have all resulted.
IV.
WHY CURRENT STANDARDS ARE INADEQUATE
The rearward ejection of occupants within a vehicle, like those discussed above, violate every precept of safe biomechanics and vehicle occupant protection dating back over fifty (50) years. The collapsing front seat violates the survival space of rear-seat occupants and rips away the safety of the seatbelt for front-seat occupants. The strength standards for automotive seatbacks should, at a minimum, be comparable to the existing minimum safety requirements for lap and shoulder seatbelts.
Why mandate minimum safety requirements for a frontal collision (i.e. the standards specifying seatbelt strength) and essentially ignore safety in rear impacts?2 Federal Motor Vehicle Safety Standard (FMVSS) 210 for frontal collisions applies to lap and shoulder seatbelts, and requires 6,000 pounds of combined load capacity. This minimum load capacity was based on testing which measured the human tolerance to impact. For example, it is well known that a 200-pound man can easily generate 6,000 pounds of total load on a restraint system in a typical 30G frontal impact. It was established over forty (40) years ago that a shoulder belt must thus withstand a minimum of 3,000 pounds load (i.e. half of the expected load) to adequately restrain the upper body of an adult in a frontal collision.
Yet those same kinds of forces can just as easily occur in a rear impact, where the only available occupant restraint is the seat itself. Be that as it is, today’s minimum standards allow seats in American vehicles that need only withstand essentially 300 pounds of loading, approximately ten percent (10%) of the safety requirement for a safety belt. (See FMVSS 207.) There is no technical, safety or rational reason to allow such weak seats in modern vehicles.
V.
THE DEFENSE POSED BY SOME MANUFACTURERS
Some automotive manufacturers try to defend these “collapsing seatback cases” by arguing that they intended for the front seats to yield to avoid soft tissue and other injuries in less severe rear collisions, and that “perfectly rigid seats” would thus be unsafe. This “defense” is nonsensical.
First, no one is suggesting “perfectly rigid seats”. The obvious solution is to provide seats that yield some, but not enough to eject front-occupants from their seatbelts during rear collisions. Secondly, no manufacturer has yet to test or specify exactly how much “yield” is needed for safety. If a manufacturer intends a seat to “yield” for safety, then it obviously should test to actually determine how much “yield” is necessary, when, and under what loading conditions. Yet to the authors’ knowledge, no manufacturer does such testing during the design process, and no manufacturer has ever quantified during the design of a particular seat exactly how much “yield” of the seat structure is required for low-impact safety. The result is simply to allow the seats to give way in rear collisions “willy-nilly”.
In addition, the rear seats in most sedans, and the front seats in standard cab pick-ups cannot yield or collapse – due to structures behind the seat that prevent them from doing so. If there was any validity to claims that manufacturers “intend” the front seats to “yield” for safety, then by that very definition, all of the rear seats in most sedans and the front seats of standard cab pick-ups are “defective” because they are designed into the vehicle so as to preclude yielding or collapse.
Finally, if present standards, allowing a manufacturer to provide a seat with only a 300-pound load capacity in rear collisions are adequate, then logically the same standards should allow a seatbelt to have only a 300-pound load capacity during frontal collisions. However, if such weak seatbelts were allowed, they would be failing by the thousands each year during frontal collisions. A national outrage would rightfully insist that it be illegal to put such seatbelts on our nation’s highways. Yet, all we need do is “turn the impact around,” and one can see the absurdity of allowing a 300-pound load capacity seat to be legally sold in the United States. They kill and maim real people, not just in theory, not just statistically speaking, but really.
VI.
EVIDENCE OF A KILLER SEAT
The aftermath of the collapsing seat can leave physical evidence in the vehicle that includes a broken seatback, a seatback permanently deformed rearward, or a seatbelt still buckled with no one in it. Other evidence can also be found in and on the recliner mechanism for the seat. For example, this evidence can include torn sheet metal near the recliners, broken recliner bolts, sheared teeth within the recliner mechanism, and even seatbelts entangled on the recliner handle of the seat.
In addition, other evidence can include bent seat frames, headrests pulled upward and bent rearward, seat tracks peeled apart or abnormally separated, abrasions showing rearward displacement of the seatbelt buckles, and deformation or abrasions on the front seatback, seat cushion and/or head restraint showing occupant movement across those surfaces. Also look for deformation and/or abrasions on the rear seat, around rear windows, and on rear decks.
Additionally, one should look for drag marks on the material headliner of the vehicle from hands, feet and other body parts. Often you can also find drag marks on the lower dashboard, center console and steering wheel from the feet of the ejected front occupant. Sometimes, there will even be abrasion marks on the seatbelt webbing itself caused by the occupant being ejected rearward as the seat fails.
VII. CONCLUSION
People are being killed, paralyzed or permanently brain-damaged each year across our country because of dangerously weak automotive seats. Clearly, the technology exists and has existed for over fifty (50) years to stop this human slaughter. And yet (with the exception of product-liability lawsuits) little to nothing is being done to put an end to it.
Minimum safety standards must be increased to provide minimal safety. Automotive seats should at least be strong enough to withstand 3,000 pounds of loading in rear collisions, just to match minimal frontal-collision safety. Arguments to the contrary simply do not withstand logic. Together we can end the associated tragedies.
1 In rear impacts with seat failure, belt slack of 7-13 inches commonly occurs. This allows the lap belt to slip off the pelvis as the occupant is ejected rearward, violating FMVSS 209, Section 4, which states that “the lap belt shall remain on the pelvis during collision and rollover. And in the aviation world, the Federal Aviation Administration (F.A.A.) requires that “seatbacks must be in the full upright and locked position” for takeoffs and landings, to assure safety by maintaining the proper geometry between seats, occupants and seatbelts. Yet, some auto manufacturers continue to distribute weak automotive seats that violate these basic principals of occupant protection by collapsing in foreseeable rear collisions.
2 NHTSA and the automotive industry in essence have no occupant protection standards for rear impacts similar to Federal Motor Vehicle Safety Standard (FMVSS) 210 for frontal collisions. Some were proposed in the early 1970's but the rulemaking was defeated after industry lobbying. Several manufacturers, however, patented stronger, safer belt-integrated seats in case those proposed standards or others ever become law.
