Seat safety: the impact of unsafe design.

To successfully handle a case involving a defective restraint system, counsel must understand the dynamics of an accident and the vehicle components that operate together to protect or injure occupants.

October 2, 1989, was a mild but rainy evening. Debra Buongiovanni and her friend James Giglio set out for an early evening movie. Debra asked James to drive her car, a 1984 Chevette. She got into the passenger seat, buckled the lap-shoulder belt, and gave James directions to the theater. This innocent social event forever changed Debra's life, and it brought to the surface corporate secrets revealing a danger found in millions of cars.

Flashback. December 14, 1966: In a report to company officials, GM engineers with the Oldsmobile Division stated that "survival is largely dependent upon front seat structure which will maintain the passengers in an upright seated position."(1)

The Chevette missed the exit. James pulled over and then backed up on the shoulder. When he reached the exit ramp, but before he could proceed, a Honda Prelude rear-ended the Chevette. In an instant, the crushing rear structure pushed the Chevette forward as both the Honda and Chevette spun around. When the vehicles stopped, the unbelted Honda driver looked around and felt a small cut on his forehead from hitting the windshield. James, also unbelted, sat in the Chevette, stunned. He looked to his right and saw Debra lying flat on her back, halfway into the back seat. He climbed out of the car and looked for help.

Flashback. June 19, 1968: In a test report, GM Engineer Thomas Ruster made the following observations:

The concept of allowing a production vehicle

front seat back to rotate rearward at a controlled

rate as a means of limiting head rotation

does not appear feasible.

Increasing the seat back height to 31 inches

does not reduce head rotation because the

occupant slides up the inclined backrest,

projecting the head and neck over the top of the

seat back.

... [P]roblems are associated with getting the

occupant to the horizontal position ... a

potential hazard can exist from the high

compressive loads imposed on the cervical spine 

as the occupant's head is being forced into the

rear seat back cushion.(2)

Debra awoke, looked around, and realized where she was lying. She was unable to move her arms or legs. Other motorists came to her rescue and stabilized her head and neck. She lay in the collapsed seat back for an hour until rescue personnel arrived and had her flown to the hospital. The workers observed the front passenger seat back lying flat in the rear of the car.

Flashback. March 12, 1982. In an internal company memorandum, GM automotive biomechanical engineers David Viano and J.J. Vostel reached the following conclusions:

"[T]he possible consequence of cervical injury

leading to quadriplegia or paraplegia is

obviously of a significant concern in the injury

prevention and improved protection of the car

occupants.

... [I]n those simulations where the seatback 

angle was greater than 60 degrees, there was

enough ... acceleration of the occupant to permit

[ramping] up the seatback with the potential for

secondary impacts of the occupant with the

automotive interior.

... [T] he following factors [are] important to

reducing potential injury in rear-end impacts ...

(3) occupant ramping up the seatback.(3)

After the fusion was performed on Debra's fractured cervical spine and she was lying in the hospital bed bolted to a halo brace, she wondered why she was paralyzed and James was walking around. Debra did not realize that on impact, the crushed rear part of the car had intruded into the rear seat area and pushed that seat up against the driver's seat back--preventing James's seat from collapsing and James from being injured. Debra wasn't so lucky. She was rendered quadriplegic.

Debra had no clue that the Chevette seat--and virtually every other front seat in the GM fleet of products produced from the 1970s to the mid-1990s--was designed to collapse rearward in impacts producing a speed change above 15 mph. Visual evidence of seat collapse was documented in GM's own crash tests.

Debra had no clue that this seat was designed so that when it collapsed, the motorist would ramp rearward in less than sixth-tenths of a second. Debra had no idea that the seat design would keep her head and neck in alignment to foster cervical spinal paralysis. Nevertheless, that is exactly what Dr. Joseph Rice, former Chief Engineer of GM Product Analysis, would tell the jury when he testified on the company's behalf in Debra's lawsuit against GM alleging defective design of the car's restraint system. After hearing the evidence from both sides' experts, the jury answered the following questions affirmatively:

* Did the right front seat of the 1984 Chevette contain a design defect when it was sold by General Motors?

* Was there an alternative, safer design practicable under the circumstances when the vehicle was sold?

* Has the plaintiff proved what injuries, if any, she would have suffered had the safer design been used?

* Was the defective design of the seat a substantial factor in causing the plaintiff's quadriplegia?

The jury awarded Debra compensatory damages to cover the cost of lifetime medical expenses and compensation for the loss of life's pleasures.(4) The total verdict reflects the jury's consideration of the dangers associated with this defective design.

Sadly, Debra's case is not an isolated incident. There are millions of cars on the road with defective seat restraints. To successfully handle these cases, counsel must become familiar with the dynamics of an accident, the vehicle components that can protect or injure occupants, and the engineering safety principles that go into making a vehicle crashworthy.

Seat design

In a motor vehicle accident, various aspects of a car's design are intended to perform as "safety systems" to ameliorate crash forces. The vehicle's structure, restraint systems, and interior surfaces are all relevant to crashworthiness because some or all of them are implicated in an accident's different phases, including the impact, crash, and injury phases.

Impact phase. During the initial phase of an accident, the collapse of the vehicle's metal structure dissipates some energy of the impact. The crush of metal structure attenuates the force and reduces the acceleration experienced by the motorists. But crush is only good if it does not permit intrusion into the occupant's survival space. Thus, cars should be designed so that their structure crushes or crumples in a controlled fashion--absorbing as much of the accident's kinetic energy as possible. Safe cars require effective "crumple zones"--designated points at which a car's structure is designed to crush and bend until the crush approaches the "survival space," and then the crush rate of the vehicle slows and the structure stiffens.

Crash phase. In this phase, after the impact, the occupant's velocity remains essentially the same as the car's pre-impact velocity until he or she is slowed by a restraint system or impacts the car's interior--or a combination of both. This is often called the "second collision." The following scenarios illustrate this principle:

* A car traveling at 30 mph collides head-on with a wall. The car stops, but the occupant continues forward at the car's pre-impact speed until the occupant is either slowed by the restraint system or hits the car's interior.

* A stopped car is rear-ended by another vehicle. The struck car moves forward, and the occupant has the car pushed out from under her at the speed the car is pushed forward.

In either scenario, as the occupant moves, the available restraint system comes into play--assuming, of course, that it is worn. In both front- and rear-end crashes, the "restraint system" is the lap-shoulder belt and the seat. It is the lap belt alone that can restrain the occupant during a rear-end collision because the occupant displaces away from the shoulder belt.

These components should be designed together to reduce the acceleration of the occupant's body and to spread the forces of the crash energy over the distance the restraint yields and over the time that the restraint system performs its function. A good system will allow the occupant to move in a controlled manner and will prevent forceful impact of the person with the car's interior.

Injury phase. In this phase, after the movement of the occupant's body has been slowed by the restraint system or by contact with the vehicle interior, the body part that contacts the restraint or interior will be stopped or impacted, subjecting it to injury-causing forces.

Catastrophic injury in motor vehicle crashes ordinarily involves the head and brain or the spine and spinal cord. Brain injury is caused by direct impact with intruding vehicle surfaces or violent contact with a non-yielding surface or indirect movement of the brain as a result of torso acceleration, which causes the brain to rotate within the skull.

Irreversible spinal cord injury in rear impacts almost always involves compressive forces imposed on the spine, which in turn impinge on the spinal cord.(5) The type of injury sustained will depend on the position of the head and neck, the impact site, the direction of cervical spine loading, and the force of the load.

A compression fracture--Debra's injury--is caused when the top of the head or the area just forward of the vertex impacts a surface while the head and neck are in flexion and the torso remains in motion while the head is stopped (akin to a diving injury). Force is then exerted on the spinal vertebrae and intervertebral disks.

Initially, the compression results in a wedging of the vertebral body as it is squeezed between the segments above and below it. When the compressive forces exceed the spine's tolerance, the vertebral body at a given point starts to bulge and break up, causing what is known as a burst fracture. During and/or after fracture, the spinal cord is compromised when it is compressed and/or when fractured bone impinges on blood flow through the cord.(6)

Nearly all serious injury in a crash occurs within the first 100 milliseconds of the accident event.(7)

The brain and spine are very sensitive to acceleration and deceleration. These organs are viscoelastic, which means that they can tolerate acceleration at low levels for a relatively long period, but as the force and acceleration increase--along with a shortened duration of time--the brain and spinal cord become more vulnerable to injury.

Thus, injury to the brain or spine is predictable from both a biomechanical and automotive design standpoint. The crux of crashworthiness design is to provide the occupant with adequate "ride down" by the restraint system so that the head and neck do not experience the injury-causing abrupt impact acceleration.

Engineering safety principles

The position of the normally seated occupant against the seat back and the crush characteristics of the rear-end structure present automakers with a mandate to provide optimal protection against impact or acceleration trauma in rear-end collisions. Since the occupant is generally against the seat back at the start of the crash, his or her subsequent motion can be limited through seat design.

The main function of the seat during a rear-end collision is to provide--in combination with restraints--a suitable surface to allow the passenger to "ride down" the crash phase without impacting other interior surfaces.(8) In Debra's case, the jury was shown published automotive safety literature and GM internal documents(9) concluding that

* Hundreds, and perhaps thousands, of motorists die or are seriously injured each year in rear-end collisions.

* Survival of front-seat occupants largely depends on front seat structure, which should maintain the passengers in an upright, seated position.

* The main function of the front seat during a rear-end collision is to provide a suitable surface for allowing the occupant to ride out the crash. The basic seat structure and the attendant substructure tying it to the vehicle chassis should be a relatively rigid load-carrying structure.

* The concept that yield by a seat back is essential to moderate collision forces during a rear-end collision has been shown to apply only to seat back designs providing inadequate support to the occupant's back and head. An adequately designed full support system should have an exceptionally rigid seat-back and head-support structure to maintain the occupant in the normal seated posture. The natural compressibility of seat-back upholstery appears to provide all the force-moderating properties required.

* Allowing the front seat back to rotate rearward can allow the occupant to move into a horizontal position in a crash. This may cause severe injury due to high compressive loads imposed on the cervical spine as the person's head is being forced into the rear seat-back cushion.

Between 1970 and 1982, there were very few written articles by any car manufacturer on the issue of seat-back safety design. In late 1980, the presidents of each of the car manufacturers received a letter from then-NHTSA Administrator Joan Claybrook recounting observations of the agency and her concerns about seat-back safety design. The letter says that "the crash tests of our New Car Assessment Program have revealed a number of seat track and seatback failures. The automakers should review their designs to insure that seats do not fail catastrophically in crashes. . . ."(10)

Soon after receiving the letter, GM's Viano initiated a series of seat tests. These took place in 1981 and 1982, when the Chevette was in design/production. Viano drew the following critical conclusions:

* The most complete study of factors associated with injury in rear-end impacts (published in 1972) identified the following factors as important in reducing potential injury in these collisions: (1) head displacement, rotation, and acceleration; (2) differential motion of the head and torso into the deflected front seat back; (3) occupant ramping up the seat back; and (4) occupant rebound.(11)

* When the seat angle exceeds 60 degrees from vertical, the dummy can move up the back of the seat, with the potential for secondary impact with the car interior.

* If a seat angle exceeds 60 degrees from vertical in a rear-end impact, an occupant may be thrown into the rear seat area and suffer serious cervical injury leading to quadriplegia or paraplegia.(12)

The 1984 Chevette front seats were not designed to provide occupant retention or to minimize occupant ramping in a rear-end collision. Rather, the Chevette seat was designed--as were all GM seats through 1996--to collapse in a rear-end collision with an impact producing a speed change above 15 mph (as visually documented in GM and other automakers' crash-test films).

Legal issues

Manufacturers are obligated to produce and sell motor vehicles that are safe and not defective. A plaintiff must prove two elements to establish a cause of action in products liability: first, that the product was defective, and second, that the defect was a substantial factor in causing injury.(13) The issue for the jury is whether the product should have been designed more safely.

Design defect claims must be submitted to a jury once the plaintiff offers evidence that the product was unsafe as designed--that the manufacturer failed to include an alternative safer system--and that that unsafe feature was a substantial factor in causing the injury.(14)

The jury in Debra's case unerringly reached the same conclusions drawn by GM's Viano when he found that (1) the applicable federal standard does not provide a realistic test of seat performance in a motor vehicle crash, and (2) in rear-end crashes such as those conducted under FMVSS 301 (30 mph moving barrier), the seat should provide sufficient occupant retention and safe biomechanical interaction to minimize the risk of serious injury.

Although the risk of catastrophic injury in rear-end collisions is significantly less than the comparable injury risk in frontal crashes (because the human body has a higher tolerance to acceleration in a rearward direction), the potential for serious injury remains. Certainly, manufacturers can design seats to provide greater strength and reduce the likelihood that motorists will ramp into the rear seat, causing injury to themselves or rear seat occupants.

Notes

(1.) OLDSMOBILE DIVISION, GENERAL MOTORS CORP., CONCLUSION OF TEST REPORT--VEHICLE REAR END STRUCTURE (1966).

(2.) THOMAS RUSTER, GENERAL MOTORS CORP., TEST REPORT PG25154--WHIPLASH PROTECTION STUDY PART VI (1968).

(3.) Research memorandum from David C. Viano and J.J. Vostal, General Motors Corp., Biomedical Science Dept., Influence of Seatback Angle on Occupant Dynamics in Simulated Rear-End Impacts (Mar. 12, 1982).

(4.) Buongiovanni v. General Motors Corp., No. 921010549 (Pa., Bucks County Cir. Ct. Sept. 25, 1997).

(5.) In low-speed, rear-end impacts, cervical strain and sprain occurs when the neck is placed in hyperextension. That phenomenon is ordinarily the result of displacement of the head and neck over either a low seat back or a head rest that may not provide sufficient resistance to bending.

(6.) ALVINS S. HYDE, A PRIMER FOR ANYONE WHO CARES ABOUT PEOPLE IN CARS (1992).

(7.) Id.

(8.) JOHN MELVIN & JAMES MCELHANEY, SOCIETY OF AUTOMOTIVE ENGINEERS, OCCUPANT PROTECTION IN REAR-END COLLISIONS, No. 720033 (1972).

(9.) Reference here to GM documents includes only those materials placed in evidence at trial.

(10.) Letter from Joan Claybrook, former Administrator, National Highway Traffic Safety Administration, to E.M. Estes, former President of General Motors Corp. (Nov. 28, 1980).

(11.) MELVIN & MCELHANEY, supra note 8.

(12.) Research memorandum from David C. Viano, supra note 3.

(13.) Czarnecki v. Volkswagen of America, 837 P.2d 1143 (Ariz. 1992).

(14.) Hammond v. International Harvester Co., 691 F.2d 646 (3d Cir. 1982).