Mercedes-Benz 2000 SLK-Class, Operator'S Manual

Page: 55 / 273

52 Restraint systems
Technical
data
Instruments
and controls
Operation Driving
Instrument
cluster display
Practical hints Car care Index
Supplemental restraint system (SRS)
Airbags are intended as a supplement to seat belts.
Airbags alone cannot protect as well as airbags plus
seat belts in impacts for which the airbags were
designed to operate, and do not afford any protection
whatsoever in crashes for which the airbags are not
designed to deploy.
The SRS uses two crash severity levels (thresholds) to
activate either the Emergency Tensioning Retractor
(ETR) or front airbag or both. Activation depends on the
direction and severity of the impact exceeding the
preset thresholds and whether the seat belt is fastened.
Seat belt fastened
• first threshold exceeded:
ETR activates
• second threshold exceeded:
airbag also activates
Seat belt not fastened
• first threshold exceeded:
airbag activates, but not ETR
Driver and passenger systems operate independently of
each other.
Emergency tensioning retractor (ETR)
The seat belts are equipped with emergency tensioning
retractors. These tensioning retractors are located in
each belt’s inertia reel and become operationally ready
with the key in steering lock position 1 or 2.
The emergency tensioning retractors are designed to
activate only when the seat belts are fastened during
frontal and front-angled impacts and rear impacts
exceeding the first threshold of the SRS and in rear
impacts exceeding a preset severity level. They remove
slack from the belts in such a way that the seat belts fit
more snugly against the body restricting its forward
movement as much as possible.
In cases of other frontal impacts, roll-overs, certain side
impacts, rear collisions or other accidents without
sufficient frontal or rear impact forces, the emergency
tensioning retractors will not be activated. The driver
and passenger will then be protected by the fastened
seat belts and inertia reel in the usual manner.
For seat belt and emergency tensioning retractor safety
guidelines see page 60.