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Occupant safety
48
Therefore, have pyrotechnic belt tensioners
which have been triggered immediately
replaced at a qualified specialist workshop.
Mercedes-Benz recommends that you have
the vehicle towed to a qualified specialist
workshop after an accident. This is particu-
larly important if a belt tensioner or an airbag
have been triggered.
An electric motor is used by PRE-SAFE
trigger the tightening of the seat belt in haz-
ardous situations. This procedure is reversi-
ble.
If the belt tensioners or airbags are deployed,
you will hear a bang, and a small amount of
powder may also be released. The 6
restraint system warning lamp lights up.
Only in rare cases will the bang affect your
hearing. The powder that is released gener-
ally does not constitute a health hazard, how-
ever it may cause short-term breathing diffi-
culties to persons suffering from asthma or
other pulmonary conditions. If it is safe to do
so, you should leave the vehicle immediately
or open a window in order to prevent breath-
ing difficulties.
Mode of operation
During the first stage of a collision, the
restraint system control unit evaluates impor-
tant physical data relating to vehicle deceler-
ation or acceleration, such as:
duration
R
direction
R
intensity
R
Based on the evaluation of this data, the
restraint system control unit triggers the belt
tensioners in the event of a frontal or rear
collision.
If the restraint system control unit detects a
high accident severity, additional compo-
nents of the restraint system are activated
independently of one another in certain fron-
tal collision situations:
Front airbags
R
Depending on the person in the front-
passenger seat, the front-passenger front air-
bag is either enabled or disabled. The front-
passenger front airbag can only be deployed
in an accident if the PASSENGER AIR BAG OFF
indicator lamp is off. Observe the information
on the PASSENGER AIR BAG OFF indicator
lamp (
page 41).
Y
Your vehicle has dual-stage front airbags. In
the first deployment threshold, the front air-
®
to
bag is filled with propellant gas to reduce the
risk of injuries. The front airbag is filled with
the maximum amount of propellant gas if the
second deployment threshold is then reached
within a few milliseconds.
The activation thresholds for the belt ten-
sioner and airbag are determined by evaluat-
ing the vehicle deceleration or vehicle accel-
eration that occurs at different points in the
vehicle. This process is pre-emptive in nature.
The triggering process must take place in
good time at the start of the collision.
The rate of vehicle deceleration or accelera-
tion and the direction of the force are essen-
tially determined by:
the distribution of the force during the
R
impact
the collision angle
R
the deformation characteristics of the vehi-
R
cle
the characteristics of the object with which
R
the vehicle has collided
Factors which can only be seen and measured
after a collision has occurred do not play a
decisive role in the deployment of an airbag,
nor do they provide an indication of airbag
deployment.
The vehicle may be deformed significantly
without an airbag being deployed. This is the
case if only parts which are relatively easily
deformed are affected and the rate of decel-
eration is not high. Conversely, an airbag may
be deployed even though the vehicle suffers
only minor deformation. This is the case if, for
example, very rigid vehicle parts such as lon-
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