REAR COLLISION CRASHWORTHINESS
Raymond Paul Johnson
Raymond Paul Johnson, A Law Corporation
2101 Rosecrans Avenue, Suite 3290
South Bay Los Angeles
El Segundo, California 90245
It’s a fact of life. In a rear-end collision, people in the
struck vehicle move rearward, towards the striking vehicle. The laws of
physics require it. As a result, your seats are your primary occupant
protection in rear impacts. This is pretty basic, yet people continue to be
killed, paralyzed or brain-damaged each year because some front seats are not
strong enough to absorb the loading of just one occupant.
As a result, the seatbacks collapse rearward causing seatbelts
to become loose around front-seat occupants, and allowing those people to ramp
up the seatbacks into the rear of the vehicle. As explained below, this can
cause life-threatening injury to both front and rear seat-occupants, as well as
loss-of-control by the driver which can result in other collisions or
These hazards are recognized by auto manufacturers and even
described in vehicle owner’s manuals which warn people never to recline their
seats while the vehicle is in motion because seatbelts become less effective.
Unfortunately, many seats are so weak that this same hazard can exist during
any moderate-to-severe rear collision, as the seatbacks collapse.
The specific dangers of collapsing seats and the lack of
adequate safety standards in this area are described below. In addition, the
telltale physical evidence showing how and why people are injured by collapsing
seatbacks is described. Finally, the author reviews defenses posed by some
defendant manufacturers in these cases, and their efficacy.
Dangers of Collapsing Seats
The deadly dangers from collapsing seats are very real, yet
continue to be largely overlooked by vehicle manufacturers, and even safety
agencies. The resulting risks endanger front-seat occupants, and people
(including babies and children) in rear seats.
As mentioned, when seatbacks collapse, those in the front
seats can be ejected rearward out of their seatbelts. These victims can suffer
head trauma, neck injury, or spinal cord damage from striking the rear seats
and other areas at the back of vehicles. This author, for example, has handled
cases across the country that have included skull fracture, permanent brain
injury, and quadriplegia.
During rear collisions, when the front-seat occupant’s head
strikes rigid or hard (unfriendly) surfaces at the rear of the vehicle, the
head stops relatively quickly. This rapid contact with rigid objects often
results in severe brain damage. For example, the head can strike metal areas
around rear windows, vertical members that support the roof (called pillars),
or other inadequately padded surfaces in the rear of the vehicle. The injury
can be combined with neck trauma if there is sufficient compression, flexion,
extension or rotation of the neck. In other instances, the front-seat
occupants can be partially or fully ejected out rear or side windows, slamming
into the road or other vehicles.
Once the front-seat driver or passenger is ejected rearward
because of the weak seatback, the head can also strike the padded rear seat,
which can bend around the head like a “baseball mitt” catching a baseball. In
those instances, the head stops relatively slowly but the body continues to
load the neck, often in compression. When enough energy remains and the body’s
tolerance to spinal loading is exceeded, severe dislocation and/or fracture of
the neck can occur.
Another mechanism of injury is rotation, where the head
stops, the body twists, and the neck is loaded. Spinal injuries in such
situations liken to the old adage that “a chain is only as strong as its
weakest link.” If the head is loaded in a seat-failure situation, the cervical
vertebrae can fail and result in quadriplegia. In some cases, 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 result. The typical situation occurs when the rearward ejected occupant’s
head misses the rear seat, and the bottom of the neck and top of the shoulders
are loaded beyond tolerance.
This author has also investigated devastating incidents
where front-seat occupants have been ejected rearward through side windows or
rear windows (called rearlights) or even hatchback windows. These
rearward-ejected occupants have hit 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 and does
and Other Rear Occupants
Collapsing front seatbacks create other dangers, including
the unacceptable risks of severe or fatal injury to those most vulnerable,
children or babies in the rear seat. This danger is particularly egregious
today because, in the 1990s, airbags were found to be killing and maiming
babies and children in the front seat. As a result, the automotive industry
and the National Highway Traffic Safety Administration (NHTSA) advised parents
to put children in the rear seat to avoid airbag hazards.
With weak seats, the resulting problem is that rearward
ejected front-seat occupants can become battering rams, smashing the heads and
chests of children. This has caused death, as well as skull fractures and
severe brain injury to children in the back seat. In addition, severe neck and
chest injuries such as ruptured hearts, torn aortas, and punctured lungs (due
to broken ribs) can result, despite the use of child safety seats. These
hazards have been demonstrated in litigation-related crash testing, as well as
in actual collisions. See Figures 1, 2 and 3, respectively.
Rear-seated occupants, both adults and children, can also be
trapped by failed front seats that collapse onto their legs. This author has
handled cases where rear-seated people have burned to death in rear impacts
simply because they could not escape from the vehicle when the front seats
collapsed onto them.
In fact, it can be virtually impossible to exit rear-seat
areas in some SUVs and vans with multiple rows of rear seats if the forward
seats collapse rearward, unless one has the time and ability to crawl up and
over the seats. The likelihood of that however becomes far less if the victims
have already been injured or entrapped by the collapsing seats.
Federal Safety Standards are Inadequate
The collapsing front seat violates the survival space of
rear-seat occupants and rips away the safety of the seatbelt for front-seat
occupants. Logic dictates that the strength standards for automotive seatbacks
should, at least, be comparable to the existing minimum safety requirements for
lap and shoulder seatbelts in frontal collisions.
They are not.
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, more than forty (40) years ago, that a shoulder belt must
therefore withstand a minimum of 3,000 pounds of load (i.e. half of the
expected load) to adequately restrain the upper body of an adult in a frontal collision.
Those same force levels 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 federal 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.
Federal Motor Vehicle Safety
Standard (FMVSS) 207 is the minimum federal standard that allows this low-level
seat strength. Because FMVSS 207 specifies no injury criteria, however, most
manufacturers agree that it is not an occupant protection standard in
the sense of FMVSS 210 (frontal collisions) or 208 (side collisions). In fact,
litigation testing in the past has demonstrated that a typical office task
chair, a typical pool-side chair and even a chair made of cardboard would pass
the strength requirements of FMVSS 207. Despite this knowledge however no occupant
protection standard with minimum injury criteria for automotive seats has ever
been established by the federal government.
Posed by Various Manufacturers
Some automotive manufacturers try to defend “collapsing
seatback cases” by arguing that they intended for the front seats to yield
in order to absorb crash energy, and/or avoid soft tissue and other injuries in
less severe rear collisions. Therefore, the argument goes, “perfectly rigid
seats” which do not “yield” are unsafe.
The counter-argument is that no one is suggesting “perfectly
rigid seats”. Stronger seats do not have to be “perfectly rigid” or rigid at
all. The solution is to provide seats that yield some, but not enough to eject
front-occupants from their seatbelts during rear collisions.
Just as importantly, no manufacturer has yet to test or
specify exactly how much “yield” is needed for safety. If a manufacturer
actually intends that a seat “yield,” then it should test to determine how much
“yield” is necessary, at what rate, and under what loading conditions, and then
establish design specifications for the yield. Without those tests, yield is
just another word for collapse. Yet to this author’s 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 should be required for safety.
In addition, all of the front seats in standard cab pick-ups
and the rear seats in most sedans cannot yield or collapse – due to structures
behind the seat that prevent them from doing so. If collapsing seats are
necessary for safety, then by definition, all of the front seats of standard
cab pick-ups and the rear seats in most sedans are unsafe or “unreasonably
dangerous” because they are designed into the vehicle so as to preclude
collapse. To the author’s knowledge, no one has ever alleged that to be true,
nor is it.
In addition, manufacturers have already developed, and
marketed and continue to market very strong front seats that do not collapse
during severe rear collisions. These include the front seat for Chrysler’s
Sebring convertible, and other belt-integrated seats used in vehicles by
Sone defense experts argue however that these seats (with
seatbelts installed within the seats rather than attached to the vehicle) have
inherent safety risks. According to them, for example, if the vehicle is hit
in an “off-set collision” (i.e. at an angle near the rear corner or side) the
seat will twist because the side of the seat with the installed seatbelt is
stronger than its other side. The twisting, so the argument goes, can cause
people to be ejected from their seatbelts towards the center of the vehicle and
be seriously injured as a result.
The counter-argument is that a solution is to simply
strengthen the weak side of the seat to preclude the twisting. At this
writing, the author has yet to hear an effective response to that
Instead, defense experts point out that belt-integrated
seats and other stronger seats have another inherent safety risk. The
argument, known as the “out-of-position” defense, goes like this: If a person
is leaning over and reaching across the car at the time of the rear collision,
when he/she moves rearward they will miss the full seatback and headrest and be
seriously injured by “knifing” at an angle across the strong seat frame.
The counter-argument is two-fold. First, the severity of
any such injury can be mitigated with proper padding. Secondly, one needs to
look at the time duration of the risk. How often do rear collisions happen
with people stretching (out-of-position) across the vehicle, as opposed to when
they are sitting normally in their seat (where the stronger seat will prevent
collapse)? Ultimately, a jury may have to decide that question. Another
question for the jury should be: Which is a greater risk needing protection - -
rear collisions where people are seated normally, or rear collisions where they
are leaning or stretching out-of-position across the vehicle?
of the Collapsing Seat
Part of prosecuting the case, of course, is proving that the
defect manifested itself in your particular collision. Fortunately, the
collapsing seat can leave physical evidence in the vehicle that includes a
broken seatback, a seatback permanently and drastically deformed rearward, or a
seatbelt still buckled with no one in it. Other evidence can be found in and
around the seat’s recliner mechanism (located at the pivot point of the
seatback and seat cushion), including torn sheet metal near the recliners,
broken recliner bolts, and/or sheared teeth within the recliner mechanism.
In addition, other evidence can include severely bent seat
frames, headrests pulled upward and bent rearward from ejected bodies, 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.
Real people, including babies and children in the rear
seats, continue to be killed, paralyzed or permanently brain-damaged each year
because of dangerously weak automotive seats. Adequate safety standards need
to be established by the government for rear-collision safety. Yet none exist,
despite the fact that technology has been in place for over fifty (50) years to
stop the carnage. Unfortunately, with the exception of product-liability
lawsuits, little to nothing is being done at present to put an end to it. That
needs to change.
. The author
wants to acknowledge gratefully the technical input and advice of seat-design
expert Kenneth Saczalski, Ph.D., and seat-testing expert Mark Pozzi that
greatly assisted in the preparation of this article.
. See 49 CFR
571.210 (1971) / Federal Motor Vehicle Safety Standard (FMVSS) 210.
. NHTSA and the
automotive industry in essence have no occupant protection standards for
rear impacts similar to Federal Motor Vehicle Safety Standards (FMVSS) 210 for
frontal collisions. Some were proposed in the early 1970s but the rulemaking
was defeated after industry lobbying. Several manufacturers, however, patented
and produced stronger, safer belt-integrated seats in case those proposed
standards or others ever become law.
. See 49 CFR
571.207 (2008) / Federal Motor Vehicle Safety Standard (FMVSS) 207.