Bracing and Tethering
rear-facing child restraints have proven to be extremely effective in
actual crashes, and experience in Sweden has shown that children through
the age of 3 can benefit as well. These large rear-facing child
restraints sit away from the vehicle seatback to give the child more leg
room and have an additional strap or other device to prevent rearward
rotation. These restraints have extremely low injury and fatality
rates, with estimates of injury-reduction effectiveness as high as 96%
when compared to the unrestrained child.
(The above link is a pdf file and require Adobe Acrobat. It will
The idea of using a
rear-facing restraint braced and tethered is fairly new in the United
States (US), and little testing has been done to prove or disprove any
benefit that may be gained from doing so. However, rear-facing
restraints in Sweden are installed and used in this manner, and have shown
great benefit and protection to children up through the age of four.
Although the Swedish restraints are significantly larger then US
restraints, there are a few US restraints that can be used in this manner,
notably the Britax Roundabout and Advantage. The Safeline
Sit-N-Stroll also has the ability to tether rear-facing, but there are
several "disadvantages" with this seat that would prevent it from being
used in this manner, namely it's low rear-facing weight limit and
necessity to be re-installed for each use. It has been noted by
respected researcher Kathleen Weber that a braced and tethered rear-facing
restraint may provide superior protection, but the benefits will be gained
by older and heavier infants and toddlers...perhaps beginning at 9 months
The principle behind
tethering and bracing a rear-facing restraint is that the restraint that
is most closely "coupled" to the vehicle will provide the most benefit in
terms of "ride-down" for the child. That is, the child will be able
to ride down the crash completely with the crushing vehicle, experiencing
a minimum of crash force and decreasing the chance for severe injury.
Not all crashes are survivable, and even the most "optimal" of restraint
cannot protect against all injury, especially in severe crashes.
Most Child Passenger
Safety experts believe that while a braced seat may provide some extra
protection in a frontal crash, the tether provides more benefit to a child
in a side impact or rear-offset crash.
restraints may be tethered either toward the front of the vehicle, down
toward the floor, or the rear of the vehicle to an existing tether anchor.
The tethered/braced rear-facing restraint is tethered toward the front and
braced against the front seat. Theoretically, the bracing eliminates
the downward rotation of the restraint, and the tether eliminates the
tethering Britax convertibles,
including how to find an anchor position for the tether connector strap.
This site offers pictures and lots of helpful information.
There are three reasons
behind the theory of positioning a rear-facing restraint against a
structure in front of it (back of front seat, or instrument panel if no
1. It will keep the restraint in a more upright orientation during a
crash, which helps keep the child from ramping up the back, loading the
shoulders into the straps, and possibly allowing the head to rise over the
top of the restraint.
2. If the rear-facing restraint is in initial contact with a vehicle
structure, the child will directly ride down the crash with the crushing
vehicle, which reduces the deceleration forces (and injury potential) to
the child. This is standard practice for large rear-facing restraints in
3. During a frontal crash, an unsupported restraint will move forward and
rotate down toward the impact point. Unless there is a large gap (varies
with each restraint, seat, crash, but perhaps 10 inches) between the
restraint top and whatever is in front of it, there will likely be contact
anyway. This hit will be harder and transfer more impact force to the
child than the situation in #2 above. It is also more likely to result in
If the gap is small or the child is on the heavy side, it is much better
to be already touching any forward structure prior to a crash than to hit
it during the crash. Resting against a forward seatback is only one way to
achieve these benefits. Another is a tether designed to be routed rearward
(Australian method) to limit forward rotation, which one manufacturer
(Britax) currently provides.
Only a few child
restraints in the U.S. have tethers
for rear-facing use, but these are common in some other countries.
Australia has tethered the top of infant restraints to an anchor
positioned behind the vehicle seat for many years, and the most popular
rear-facing "capsule" will not work properly if it is not tethered.
Australians have also generally kept infants rear-facing until only about
6 months, when they start to use a forward-facing and virtually-always
tethered restraint. Tethering a rear-facing CR toward the rear of the
vehicle, which describes the Australian method, limits the downward
rotation of the restraint and child during a frontal crash but does
nothing to affect initial stability, rebound, or rear-impact.
Sweden has always used rear-facing restraints for children up to 4 years
old, when they are moved directly into boosters with lap-shoulder belts.
These large rear-facing restraints, which are set several inches away from
the vehicle seatback to provide leg room, must rest against a vehicle
structure, such as the instrument panel (unless there is an air bag) or
the back of the front seat to keep them from falling over. Since the CR
and its occupant can be tall and heavy, the Swedes have also tethered the
backs down to the floor to eliminate rearward rotation during rebound or
rear impact. The Swedes also have some small infant-only restraints that
are not tied to the floor but do use the shoulder portion of the
lap-shoulder belt to wrap around the "front" (the child's back) of the
restraint to limit rotation during a crash. This installation method is
used throughout Europe for frontal crash protection, but there is little
effect on rebound or rear-impact motion.
The first U.S. infant restraint, which is the model for subsequent ones,
did not use a tether in either direction nor a shoulder belt, but it
worked very well. During development, the engineers observed that it
turned over toward the vehicle seatback after a crash test and, largely in
order to justify what happened anyway, they called this the "cocoon
effect." There was also some justifiable concern that the small infant's
neck might be injured on rebound or rear-impact unless the restraint were
allowed to freely rotate in this direction. Justified or not, this concept
has remained and seems to make intuitive sense. The counter-argument that
the infant's head will "slam" into the seatback and be injured on rebound
has not been validated in nearly 30 years of accident experience.
Britax, which has operations in Australia, Sweden, UK, and Germany, as
well as in the U.S., devised a means to tie a traditional U.S. rear-facing
convertible down to the base of the front seat structure to give it a firm
installation and help the parent achieve something close to a 45° back
angle, or more upright as appropriate. This tether does achieve a very
secure installation, which is reassuring for parents, but it does little,
if anything, to improve protection in a frontal crash. Downward
rotation will likely be limited more by the back of the front seat than by
any cushion compression achieved with a tight downward tether. Another
concern is that parents may use the tether to make the CR too reclined.
The restraint models on which this is offered, however, can accommodate a
child up to 30 lb rear facing, and for this usage the limit on rebound or
rear-impact motion may be beneficial. Although crash experience indicates
that rebound of infant-only restraints in frontal impacts does not cause
serious injury, similar movement of a rear-facing restraint can also occur
during a severe rear impact or offset rear impact, which can result in
serious injury or death if the infant's head hits the rear door pillar of
a sedan, the rear window of a pickup, or some other hard surface. As
larger and heavier infants are carried rear-facing, the chance of an
infant's head hitting a hard part of the vehicle is greater. Tethering a
rear-facing convertible CR to the floor can reduce the risk of head and
facial injuries in rear and side crashes by reducing head excursion.