In this article:

• Yielding Seats vs. Rigid Seats
• A Brief Look at One Automobile Manufacturer, General Motors
• Alternative Designs
• Conclusion

As early as 1969, Derwin Severy, in a paper titled “Safer Seat Design” (SAE690812) called the automobile seat the “most important single lifesaving device available.” Unfortunately, each year approximately 1,200 people die in rear-end collisions and thousands more are terribly injured. Many of these deaths and injures are caused by the partial or total failure of the restraint systems meant to protect occupants in rear-end impacts. In a rear-end collision, the car seat becomes an intrinsic part of the restraint system, as noticed in this warning found in the owner’s manual of the 1988 Ford Mustang: “The protection provided by the seat and shoulder belts is significantly reduced when the seat back is not in the upright position.”

When a vehicle is impacted from the rear, the forces of the impact propel the vehicle forward and the occupants are thrown backwards. The seat and seat belts, if properly designed, should keep the occupant upright and prevent the occupant from ejection, striking interior components or other passengers. However, if seat back failure occurs, the use of the seat belt system may not prevent the occupant from injury. As a result of this dangerous condition, drivers and passengers are exposed to the serious risks of head and neck injury or fatality.

When a seat collapses rearward in a rear-end collision, the potential for a number of safety problems arise. These include but are not limited to:

• Front seat occupants can be partially or completely ejected from the vehicle after having slid out from beneath their lap-shoulder belt restraints;
• A front seat collapsing can cause serious injury or death to the rear seat occupants trapped underneath the collapsed seat back or struck by the front seat occupants; and
• The driver can lose control of a vehicle if unable to sit upright while the vehicle is in motion.

Meeting and Exceeding the Federal Motor Vehicle Safety Standard Requirements
The hazard of seat back failure originates from the inadequate Federal Motor Vehicle Safety Standard (FMVSS) 207 – Seating Systems. The current standard requires inadequate seat strength to ensure that the seat does not fall when a car is subjected to a rear impact. The current standard, which has not been updated in over thirty years, requires that a seat withstand a load equal to a 3,300 inch-pounds applied about the seat back in a rearward direction. The standard does not contain dynamic crash impact test requirements for seats in rear crashes. Even though seat backs regularly fail during National Highway Traffic Safety Administration (NHTSA) 30-mph rear impact crash tests to evaluate fuel tank integrity (FMVSS 301).

It is not difficult for an automobile seat to meet or exceed the existing thirty year old standard. In fact, today’s standard is so poor that a folding aluminum lawn chair has been able to pass the strength requirements as well as vehicle seats from the 1940s. In comments made to NHTSA, auto manufacturers have typically taken the position that their vehicles already exceed the federal seat back strength requirement. Furthermore, their seats were designed to collapse or fall back in the event of a collision.

The present standard has been in existence since the late sixties. In 1974, plans by NHTSA to upgrade the standard were abandoned in the face of auto industry opposition. In 1980, NHTSA made another attempt at addressing the issue by writing to the automobile manufacturers noting a disturbing pattern of seat failures in NHTSA’s new car testing.

In 1989, NHTSA was petitioned twice by independent safety engineers to initiate rulemaking to strengthen its existing standard. One of the petitioners, Dr. Kenneth Saczalski requested that NHTSA increase the seat back standard 17-fold, arguing that such a standard was achievable using state-of-the-art materials and design. NHTSA granted the Saczalski petition stating that his proposal to stiffen seat backs “warranted further consideration.” After a flurry of negative comments from the automakers opposing Saczalski’s recommendations, the agency, once again, backed off rulemaking choosing instead to launch research into the issue of seat back strength.

By 1992, NHTSA concluded that improving seating systems was a more complex issue than simply increasing seat back strength and that seats needed to be better integrated with head restraints and seat belts. Although the NHTSA has indicated its desire to strengthen the requirements of FMVSS 207, it has yet to make any changes to the standard.

Yielding Seats vs. Rigid Seats

There are two schools of thought regarding seat back performance in rear impacts - yielding seats vs. rigid seats. For the most part, the auto manufacturers have taken the position that yielding seats are safer than rigid seats. Their position is based on the premise that vehicle occupants need to be able to “ride down” a rear impact collision. Therefore, the seats need to yield in a “controlled” manner to absorb the energy. The automakers contend that occupant kinematics, in the real world, would be negatively affected with more rigid seat backs because occupants can ramp up or rebound against a rigid seat back.

Proponents for rigid seats point out the high incidence of ejection as a significant hazard when a seat collapses. Other problems cited include: the loss of vehicle control, reduced restraint system effectiveness, injury to rear seat occupants, and serious injury from impacts with interior components. In a study of twenty-three rear impact collisions with front seat failure, the majority of the front seat occupants were either partially or totally ejected even at velocity changes of 18 mph or less, according to its author, Dr. Kenneth Saczalski.

A Brief Look at One Automobile Manufacturer, General Motors

In comments to the NHTSA, auto manufacturers have defended yielding seat backs, even though their own internal documents suggest that stronger seats result in improved occupant kinematics and the potential for the reduction of injuries and deaths.

General Motors Corporation (GM) knew, as early as 1966, that seat strength is directly related to occupant safety in a rear impact collision, and that occupant survival depended largely upon a front seat structure that held the passenger in an upright seated position. For years, GM has aggressively protected its internal documents related to discussions of seat back design or failure. Lawsuits against GM often settle with provisions that victims not release any damaging information about the manufacturer. But internal GM documents have revealed that its personnel have repeatedly questioned the safety of GM’s own seat back design.

According to documents obtained by CBS for its series on seats collapsing in rear-end collisions, in 1992, GM attorneys advised top executives that yielding seats could no longer be defended. One internal memo concluded, “We are unable to effectively demonstrate that we exercised ‘reasonable care’ as a caring corporation.”

The auto industry has repeatedly ignored its own engineers. A leading GM engineer, David C. Viano, in a 1994 internal GM study, projected that 376 to 470 lives could be saved each year and estimated that improvements would prevent 1,000 serious injuries each year in rear-end collisions if the company strengthened its seat backs. Another GM litigation study of 25 seat back failures found that 19 deaths and/or injuries could have been reduced had GM installed stronger seats.

It is not only General Motors’ vehicles that suffer from seat back failures. NHTSA has received complaints of seat backs collapsing in more than two dozen different cars, including models made by all of the American automobile manufacturers.

Alternative Designs

Many claim that the solution to seat back failure is integrating seatbelts within the seat structure. A system that combines strengthening the seat in a rear crash and holding the passenger in the seat in an upright position would be most favorable.

Integrating seatbelts within a seat structure is not necessarily a new concept. Below are examples of this concept being developed and utilized in automobiles:

• The Cox Safety Seat was developed in the 1960s. It was a rigid seat with seat belts mounted to the seat itself;
• Belt integrated seats were found in the Range Rover as early as 1970;
• In 1972, Ford equipped its Experimental Safety Vehicle (ESV) with rigid seats and tested it in rear impacts at speeds of 50 mph;
• In 1989, BMW presented a paper embracing the benefits of belt integrated seats, specifically mentioning the improved protection offered in rollover collisions;
• The 1991 Mercedes SL was equipped with integrated seats and belts;
• In 1992, Starcraft, a maker of conversion vans and recreational vehicles, asked its engineering staff to come up with a solution to the growing concern about seat back failures. Their solution was the patented “Integrated Belting System;”
• The 1995 European Ford Transit van was fitted with integrated seats and belts;
• The 1996 Chrysler Sebring convertible was equipped with integrated seats and belts;
• The 1997 European Mercedes V-Class minivan’s rear seat was fitted with integrated lap and shoulder belts;
• Integrated seatbelts were offered on the 2000 model Buick LeSabre; and
• By 2001, integrated seats and belts were standard in some models of the following makes of automobiles: Acura, BMW, Chrysler, Honda, Kia, Chevrolet, GMC, Mercedes Benz, Oldsmobile, Pontiac, Rolls Royce.

Conclusion

Advances in technology have made possible significant improvements in the ability of automotive seats to add appreciable crash victim occupant protection, especially with the advent of integrated seat concepts. The seat strength standard does not suffice in preventing fatalities or serious injuries. It is not enough for auto manufacturers to meet this antiquated standard. Neither today’s technology nor the inadequate federal seat back strength requirement prevent the auto manufacturers from strengthening seats before the government moves to require such action.