Seat Belt Injury Information

Seat Belt Failure and Injury When Seat Belts Fail

When an occupant is killed or seriously injured in a car accident despite wearing his or her seat belt, it is reasonable to ask why did the seat belt fail.

The Basic Principles of Seat Belts

A typical auto crash can be viewed as having two collisions. The “first collision” occurs when the vehicle impacts another vehicle or a fixed object. The “second collision” occurs when a vehicle occupant impacts the interior of the vehicle or is ejected and hits the ground. The second collision immediately follows, often only by milliseconds, the first collision. The purpose of a seat belt is to either prevent the second collision or minimize its injury-producing potential. A snug fitting lap and shoulder belt “ties” the occupant to the passenger compartment and allows him or her to “ride down” the crash, thereby minimizing or eliminating injurious occupant contact with the vehicle interior, such as the windshield, steering wheel or the roof.

Evidence that a seat belt failed because of design or manufacturing defects is often subtle and can be difficult to detect. If a belt failure is suspected, the most important thing to do is preserve the vehicle and the seat belt system since it is extremely difficult to prove that a seat belt failed without the physical evidence.

How a Seat Belt Retractor Works

Seat Belt Failure Cause Injuries

In many instances, injury to a belted occupant is due simply to crash forces and the inescapable violence involved in car wrecks. After all, seat belts cannot immunize us from injury in a collision. However, in a still significant number of cases, the injury would not have occurred but for a defect in the seat belt system.

Seat belts fail to restrain occupants due to both poor design and faulty manufacturing. Some of the more common defects include:

Inertial Unlatching & False Latching

Inertial unlatching occurs when the seat belt becomes unlatched during a collision, allowing the latch plate to pull out of the buckle. Though the auto industry denies that a seat belt can inertially unlatch, recent testing has demonstrated how accident level forces can cause the buckle “pawl” or button to depress and release the latch plate. Millions of vehicles have seat belts that are susceptible to this phenomenon.

False latching occurs when the latch plate looks, feels and even sounds like it is latched when inserted into the buckle but is not fully engaged. Minimal amounts of force will cause a falsely latched buckle to completely release the latch plate. When a seat belt is falsely latched or becomes inertially unlatched, the occupant is essentially unbelted and unrestrained and moves as though he or she were never belted in the first place. Such occupants are frequently ejected or found unbelted inside the car.

Though the occupant was properly belted before the seat belt became unlatched, the police report will often list the occupant as being unrestrained. Cases involving inertial unlatching or false latching frequently arise when either a surviving occupant insists he or she was belted or when other occupants confirm that the deceased occupant was wearing a seat belt.

Torn or Ripped Webbing

When the seat belt tears or is ripped in half during an accident, something has probably gone terribly wrong. Seat belt webbing is designed to withstand the forces of most survivable collisions without ripping or tearing. Torn or ripped webbing might occur because of a defect or manufacturing flaw in the webbing itself, such as material or weaving deficiencies.

Torn Seat Belt By a Sharp Edge on Seat

Ripped or torn webbing might also be the consequence of some other vehicle defect. Any defect that allows excessive slack or payout of the webbing can cause the belt to be “snap-loaded” – loaded too rapidly, which can sever the webbing. Sharp or protruding edges of vehicle components can also cut through the seat belt. In one recent case, a bending belt anchor moved the belt into contact with a sharp seat support.

Seat Belt Retractor Failure

Seat Belt Retractor Device

During an accident, the seat belt retractor “locks” the seat belt webbing and holds the occupant in place. When the retractor fails to properly lock, excessive webbing “pays” out of the retractor and results in seat belt “slack.” Sometimes as little as a few inches of “slack” can mean the difference between an injury-free event and catastrophic or fatal injuries. In a frontal collision, for example, a snug shoulder belt should restrain the occupant in the seat and prevent injurious contacts with the steering wheel and windshield. A slack or loosely fitting shoulder belt might allow the occupant to move forward and contact these objects.

Retractors can fail to lock because of design defects as well as manufacturing defects. One failure mode of certain “direct drive” retractors is a phenomenon known as “skip-lock” or “skipping” – which occurs when the retractor lock bar hits the tip of a ratchet tooth and bounces away instead of engaging the root of the tooth and locking the webbing. Auto manufacturers vehemently deny that skip-lock can occur, but it has been documented in the literature as well as in General Motors’ internal research projects.

How Skip-Lock Occurs

“Windowshade” devices

Most U.S. cars manufactured from the late-1970s to the late 1980s contained a “tension-relieving” device in the retractor, which, by design, introduces slack into the shoulder belt. These so-called “windowshade” devices operate much like a household windowshade – when the belt is pulled out of the retractor, the device engages and the belt remains in its new position.

Windowshade Device

One consequence of the windowshade design is the inadvertent formation of excessive amounts of seat belt slack. By design, windowshade retractors permit occupants to intentionally introduce slack into the shoulder belt. Occupants can also unknowingly introduce slack into the shoulder belt by moving forward to reach for the radio or other items. As mentioned, slack undermines the effectiveness of a seat belt in an accident and can result in severe head impacts with the steering wheel, dashboard or windshield.


Poor Seat Belt Geometry

Seat Belt Design & GeometryPoor belt geometry can contribute to excessive occupant excursion, particularly in rollovers. The best location for seat belt anchors is on the seat itself, yet many vehicles have anchors located on the vehicle floor, often behind the occupant’s seat. The resulting shallow belt angle can permit excessive excursion toward the roof in a rollover. Poor D-Ring locations can also adversely affect geometry and belt effectiveness. Adjustable D-Rings have improved overall geometry but have only become popular in more recent vehicles.


Vehicle “System” Failure

To be effective, seat belts must work in conjunction with the vehicle’s seats and surrounding structure. If the seats fail or there is significant roof crush or occupant compartment intrusion, seat belt effectiveness is reduced. In many accidents, occupants are injured or killed due to a combination of vehicle failures, such as excessive roof crush combined with inadequate restraint by the seat belt.

Door-mounted and Other Automatic Belt Systems

These systems pose a slew of safety risks, including occupant ejection when the door opens during a crash and severe spinal cord injuries when an occupant with an automatic shoulder belt forgets to put on the manual lap belt.

Lap-only Belt Designs

Lap-only Seat Belt DesignThough the benefits of utilizing a lap and shoulder belt have been known for decades, shoulder belts were not included in the rear seats of most U.S. cars until the late 1980s. Lap-only belts can lead to fatal or catastrophic injuries, including head, spinal cord and other internal injuries.


When To Suspect a Seat Belt Failure

Seat belt performance and potential effectiveness is highly dependent upon the facts of an individual accident. While it is difficult to generalize, the following facts, if present, might indicate a seat belt problem:

  • Both serious and non-serious injuries to belted occupants. For example, if one belted occupant walks away while another belted occupant is paralyzed or suffers a serious head injury.
  • An injured occupant is found wearing a loose-fitting seat belt. This could indicate the presence of excess slack.
  • An occupant is found unbelted but either the occupant or other passenger insists he or she was seat belted. This could indicate inertial unlatching or false latching.
  • An occupant in a frontal collision makes contact with the windshield. This might indicate the presence of excess slack or retractor failure.
  • A seriously injured belted occupant in a vehicle with limited structural damage. For example, if there is limited roof crush and limited intrusion into the occupant compartment during a rollover yet a belted occupant sustains head or neck injuries.
  • Serious injuries in a minor to moderate collision. When a restraint system works properly, occupants typically should not receive serious injuries in minor or moderate speed collisions.
  • The seat belt webbing is torn or ripped or the seat belt is pulled loose from its anchors. This could be indicative of either a seat belt defect or some other type of vehicle defect.

The Seat Belt Market

Seat Belt Manufacturing RevenueSeat belts are big business. For example, a major supplier of U.S. seatbelts and airbag components is Takata of Japan. Takata, a global manufacturer of automotive safety systems, is one of the largest suppliers of complete safety systems in the world.Takata produces a full line of seatbelt systems and components, airbag modules and inflators, electronic sensor units and modules, steering wheels and clocksprings, as well as a broad range of interior trim components.

Seat Belt MarketTakata Global Group is a major supplier of safety systems components to Honda, GM, Ford, Nissan, Toyota, and DaimlerChrysler. In Fiscal Year 2002, Takata generated over $2,500,000,000. Takata’s global operations include 48 plants and 40 companies (eg., TAKATA, INC. (Delaware Corp.), TAKATA NORTH AMERICAN, INC., TAKATA CORPORATION(foreign corp.)) in 16 countries with 29,000 employees. See,



2 thoughts on “Seat Belt Injury Information

  1. My husband was driving home with my children last Friday the 20th of January and was hit on the passenger side of the vehicle and none of the seat belts locked. My 6 and 7 year old girls in the 3rd row seat were thrown forward and luckily for my 7 year old the seat in front of her was up so they could get in the car so she only got a black eye from her backpack flying up and hitting her. My 6 yr. old was taken to the ER where they found blood in her urine and diagnosed bruised kidneys. Well me being them Mom that I am was furious that the seat belts didn’t lock when they were suppose to protect my children. I emailed GM because our car is a 2007 Yukon XL and they are sending a Wreck Investigator or whatever they call themselves out to take a look. My question to you is what should I do to protect my rights? Should I worry about him coming should I have a lawyer there with me what should I do so I can protect my family from this happening again? Thank you, Shawnna Lazo
    • Ms. Lazo, I am sorry to hear about your ordeal. Yes, a lawyer can protect your rights in this situation, and such matters are handled by this office on a contingency arrangement (meaning no fee if no recovery). First and foremost, the vehicle cannot be altered in any way, and must be preserved in ‘as is’ condition after the accident for investigation by BOTH SIDES CONTEMPORANEOUSLY. While the GM folks should be aware of this, I would not trust them as I have heard of parts being removed and replaced, etc. We have procedures that we follow to ensure this does not occur, or if it does occur without your consent, your rights will be protected. Please feel free to contact me for additional assistance or information. I would be glad to help. Good luck to your children, I hope their injuries are minor and temporary. Jim Avery

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