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Competence in Safety.
A pioneer in automotive safety.
Mercedes-Benz has been passionate about making cars – each one even better than the
last – from day one. Since the first models invented by Gottlieb Daimler and Karl Benz,
cars have become not only faster but also more comfortable and considerably safer. And
even though the volume of traffic on our roads has increased several-fold, the safety risks
to the driving public remain relatively low thanks to the enormous progress made in the
areas of active safety (accident prevention) and passive safety (minimizing injury during
accidents). Mercedes-Benz has made key contributions in these fields with a safety
development program spanning several decades. Safety-conscious design has always
been and remains a vital aspect of Mercedes-Benz passenger car development.
Many new developments in automotive safety first saw the light of day in a Mercedes,
often long before they appeared in other vehicles. As a result, the Merc\
has become synonymous with automotive safety around the world. Seat belts and air bags
are perhaps two of the most well known – and still most effective – passive safety
features. Mercedes-Benz first offered its customers 3-point seat belts in1968; and, in
1980 was the world's first automotive manufacturer to install front airbags in standard-
In order to understand how seat belts and air bags provide protection, it is important to
realize what happens to vehicle occupants in an accident. Upon impact, a vehicle is either
decelerated rapidly (when colliding with another vehicle or object) or accelerated (when
hit by a moving object such as another vehicle). When the vehicle is decelerated or
accelerated in this way, inertia always causes the occupants to move toward to the area of
impact. Restraint systems are required to reduce the risk of contact bet\
occupants and the vehicle interior caused by this occupant movement. Such systems
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primarily include seat belts, ideally supplemented by seat belt emergency tensioning
devices with force limiters where appropriate, and with air bags.
The protective capabilities of these systems can only be fully realized if seat belts are
used on every trip: always buckle up everyone and then drive. Wearing a seat belt alone
can prevent many injuries or lessen the severity of injuries in various types of accidents,
whereas an air bag on its own cannot provide the same degree of protection, since it is
designed only to supplement the protective effect of the seat belt afforded to an occupant
properly wearing a seat belt in certain types of accidents. Consequently\
, the air bag and
related seat belt emergency tensioning device systems in Mercedes-Benz vehicles are
called a Supplemental Restraint System (“SRS”). While the seat belts and air bags in
combination provide substantial protection in accidents, injuries and even fatalities can
nevertheless occur in accidents exceeding the protective capabilities of these safety
systems. To name only one example, properly worn seat belts and deploying air bags
even in combination cannot generally prevent the risk of injuries from intrusions into the
Seat belts are vital.
The seat belt is the single most important
restraint system in the vehicle. When worn
correctly, it reduces the possibility or
severity of the occupant striking the
interior of the vehicle or the likelihood that
the occupant will be ejected from the
vehicle in an accident. A properly worn
seat belt also helps to hold the occupant in
the proper position in relation to the air bag
so that the occupant can benefit from its
deployment, if required.
Furthermore, failure to properly wear a seatbelt increases the possibility of injury from a
deploying air bag. All occupants must therefore properly fasten their seat belts before
every trip. See your operator’s manual for additional information regarding proper seat
Emergency tensioning devices and seat belt force limiters.
The front and some outboard rear seat belts are equipped with emergency tensioning
devices (ETDs), some with belt force limiters. When deployed in an accident, an ETD
takes up slack on the seat belt to help increase the effectiveness of th\
e seat belt by
allowing restraining contact between the belt and occupant earlier in the accident
sequence. However, an ETD cannot rectify incorrect seating positions, nor can it adjust
incorrectly worn seat belts or pull occupants back into the seat backres\
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Seat belt height adjustment ETD in installation position
If the seat belt is also equipped with a seat belt force limiter, the limiter, when activated,
helps to reduce the peak force exerted by the seat belt on the occupant.\
The seat belt
force limiter is also designed to work with a deploying front air bag by providing mo\
even distribution of occupant restraining forces between the seat belt and air bag.
The ETD is designed to be activated only if the seat
belt is fastened and the vehicle’s ignition is on, during
a frontal or rear-end collision generating a frontal
deceleration or rear acceleration rate sufficient to meet
the system’s deployment threshold. ETDs in vehicles
equipped with rollover sensors will also deploy during
a lateral rollover if the sensor determines that
potential additional protection can be provided.
In vehicles equipped with an occupant sensor for the
front passenger seat, the ETD will only be activated if
the sensor detects an occupant in the seat or if the seat
belt is fastened.
The driver-side ETD will only be activated if the belt is fastened. To operate at the speed
necessary to increase belt effectiveness in an accident, the ETD is oper\
pyrotechnically and may thus release some harmless smoke into the passenger
compartment. Upon activation of the ETD, the SRS indicator lamp comes on or a
diagnostic code is stored in the SRS control unit.
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Supplemental Restraint Systems.
What happens when an air bag is deployed?
During deployment, an air bag inflates within a small fraction of a seco\
nd during the
actual collision in order to provide the occupant with additional protection beyond that
afforded by the seat belt. As inflation must be very rapid to afford protection in the very
short accident sequence, deployment results with a relatively loud noise\
. When the
occupant is properly positioned, contact between the occupant and the inflated air bag
helps prevent or reduce the severity of the occupant’s striking interior surfaces of the
The front air bag or side impact air bag will deflate through vent holes or a permeable
fabric after inflation in order to provide the intended occupant restraint. The gases that
are used to inflate the air bag are hot when expelled from the inflator into the air bag
itself and cool down relatively rapidly when they mix with the atmosphere within the
vehicle. However, escaping gases can cause injury if body parts such as hands come into
contact with them. Additionally, the inflator remains hot and should no\
t be touched after
inflation. Also, air bag inflation can result in some harmless smoke or dust being
released into the passenger compartment.
Available restraint systems for the E-Class (W 211)