2012 MERCEDES-BENZ A CLASS brake

PRE-SAFE
®
takes pre-emptive measures to
protect occupants in certain hazardous sit-
uations.
PRE-SAFE ®
intervenes:
R when BAS activates, e.g. in emergency
braking situations
R when adaptive Brake Assist intervenes
powerfully on vehicles with DISTRONIC
PLUS
R in
critical driving situations, e.g. when phys-
ical limits are exceeded and the vehicle
understeers or oversteers severely
PRE-SAFE ®
takes the following measures
depending on the hazardous situation detec-
ted:
R the front seat belts are pre-tensioned.
R vehicles with the memory function: the
front-passenger seat is adjusted if it is in an
unfavourable position.
R if the vehicle skids, the panorama sliding
sunroof and the side windows are closed so
that only a small gap remains.
If the hazardous situation passes without
resulting in an accident, PRE-SAFE ®
slackens
the belt pretensioning. All settings made by
PRE-SAFE ®
can then be reversed.
If the seat belts are not released:
X Move the backrest or seat back slightly, but
only when the vehicle is stationary.
The belt pretensioning is reduced and the
locking mechanism is released.
More information about seat belt adjustment,
a convenience function integrated into PRE-
SAFE

(Y page 47). Seat belts
Important safety notes G
WARNING
A seat belt which is not worn correctly, or
which has not been engaged in the seat belt
buckle

correctly, cannot provide the intended
level of protection. Under certain circumstan- ces, this could cause severe or even fatal inju-
ries in the event of an accident.
Therefore, make sure that all occupants — in
particular,

pregnant women — wear their seat
belts correctly at all times.
R The seat belt must fit snugly on your body
and must not be twisted.Therefore, avoid
wearing bulky clothing, e.g. a winter coat.
The shoulder section of the belt must be
routed across the centre of your shoulder
— on no account across your neck or under
your arm — and pulled tight against your
upper body. The lap belt must always pass
across your lap as low down as possible, i.e.
over your hip joints — not across your abdo-
men. If necessary, push the seat belt
slightly downwards and adjust it by pulling
it in the direction the seat belt retracts.
R Do not route the seat belt strap over sharp
or fragile objects. Please make sure that
such objects are not on or in your clothing,
e.g. spectacles, pens or keys etc. The seat
belt strap could become damaged and tear
during an accident and you or other vehicle
occupants could be injured.
R Only one person should use each seat belt
at any one time. Children must never travel
sitting on the lap of another occupant. The
child will not be secured in the event of an
accident, heavy braking or sudden change
of direction. This may result in the child or
other occupants being seriously or fatally
injured.
R Persons under 1.50 m tall cannot wear the
seat belts correctly. For this reason secure
persons less than 1.50 m tall in specially
designed, suitable restraint systems.
R Children under 1.50 m tall and younger
than twelve years of age cannot wear the
seat belts correctly. For this reason secure
them in special suitable child restraint sys-
tems installed on a suitable seat. Additional
information can be found in the Operating
Instructions in the chapter "Safety", "Chil-
dren in the Vehicle". Observe the installa-46
Occupant safety
Safety

opened from inside the vehicle. When the
vehicle is unlocked, the door can be opened
from the outside.
X
To activate: press the child-proof lock
lever up in the direction of arrow :.
X Make sure that the child-proof locks are
working properly.
X To deactivate: press the child-proof lock
lever down in the direction of arrow ;.
Override feature for the rear side win-
dows X
To activate/deactivate: press button :.
If indicator lamp is lit, operation of the rear
side windows is disabled. Operation is only
possible using the switches in the driver's
door. If the indicator lamp is off, operation
is possible using the switches in the rear
compartment. Driving safety systems
Driving safety systems overview
In
this section, you will find information about
the following driving safety systems:
R ABS ( Anti-lock Braking System)
(Y page 61)
R BAS ( Brake Assist System) ( Y page 62)
R COLLISION PREVENTION ASSIST (adaptive
Brake Assist and distance warning func-
tion) (Y page 62)
R Adaptive brake lamps ( Y page 65)R
ESP ®
(Electronic Stability Program)
(Y page 65)
R EBD ( electronic brake force distribution)
(Y page 69)
R ADAPTIVE BRAKE

(Y page 69)
R STEER CONTROL ( Y page 69) Important safety notes
If you fail to adapt your driving style or if you
are

inattentive, the driving safety systems can
neither reduce the risk of accident nor over-
ride the laws of physics. Driving safety sys-
tems are merely aids designed to assist driv-
ing. You are responsible for the distance to
the vehicle in front, for vehicle speed and for
braking in good time. Always adapt your driv-
ing style to suit the prevailing road, weather
and traffic conditions and maintain a safe dis-
tance from the vehicle in front. Drive care-
fully.
i The driving safety systems described only
work as effectively as possible when there
is adequate contact between the tyres and
the road surface. Pay particular attention
to the information regarding tyres, recom-
mended minimum tyre tread depths etc. in
the "Wheels and tyres" section
(Y page 318).
In wintry driving conditions, always use
winter tyres (M+S tyres) and, if necessary,
snow chains. Only in this way will the driv-
ing safety systems described in this section
work as effectively as possible. ABS (Anti-lock Braking System)
Important safety notes i
Observe
the "Important safety notes" sec-
tion for driving safety systems
(Y page 61). G
WARNING
If ABS is faulty, the wheels could lock when
braking. The steerability and braking charac- Driving safety systems
61
Safety
Z

teristics may be severely impaired. Addition-
ally, further driving safety systems are deac-
tivated.
There is an increased danger of skid-
ding and accidents.
Drive on carefully. Have ABS checked imme-
diately at a qualified specialist workshop.
If ABS is malfunctioning, other systems,
including driving safety systems, will also
become inoperative. Observe the information
on the ABS warning lamp ( Y page 258) and
display messages which may be shown in the
instrument cluster (Y page 230).
ABS regulates brake pressure in such a way
that the wheels do not lock when you brake.
This allows you to continue steering the vehi-
cle when braking.
ABS works from a speed of about 8 km/h
upwards, regardless of road-surface condi-
tions. ABS works on slippery surfaces, even
when you only brake gently.
The ! ABS warning lamp in the instrument
cluster lights up when the ignition is switched
on. It goes out when the engine is running.
Braking X
If ABS intervenes:
continue to depress the
brake pedal with force until the braking sit-
uation is over.
X To make a full brake application:
depress the brake pedal with full force.
If ABS intervenes when braking, you will feel
a pulsing in the brake pedal.
The pulsating brake pedal can be an indica-
tion of hazardous road conditions, and func-
tions as a reminder to take extra care while
driving. BAS (Brake Assist)
i Observe

the "Important safety notes" sec-
tion (Y page 61). G
WARNING
If BAS is malfunctioning, the braking distance
in an emergency braking situation is
increased. There is a risk of accident.
In an emergency braking situation, depress
the brake pedal with full force. ABS prevents
the wheels from locking.
BAS operates in emergency braking situa-
tions.

If you depress the brake pedal quickly,
BAS automatically boosts the braking force,
thus shortening the stopping distance.
The brakes will function as usual once you
release the brake pedal. BAS is deactivated. COLLISION PREVENTION ASSIST
General notes COLLISION PREVENTION ASSIST consists of
the adaptive Brake Assist and the distance
warning signal, which are described in the
following.
Distance warning function
Important safety notes
i
Observe

the "Important safety notes" sec-
tion for driving safety systems
(Y page 61). G
WARNING
The distance warning function does not react:
R to people or animals
R to oncoming vehicles
R to crossing traffic
R when cornering
Thus, the distance warning function cannot
provide a warning in all critical situations.
There is a risk of an accident.
Always

pay careful attention to the traffic sit-
uation and be ready to brake. 62
Driving safety systems
Safety

G
WARNING
The distance warning function cannot always
clearly identify objects and complex traffic
situations.
In such cases, the distance warning function
may:
R give an unnecessary warning
R not give a warning
There is a risk of an accident.
Always
pay careful attention to the traffic sit-
uation; do not rely on the distance warning
function alone.
Function
X To activate/deactivate:
activate or deac-
tivate the distance warning function in the
on-board computer (Y page 218).
Vehicles with a black and white multi-
function
display: when the distance warning
function is activated, the Ä symbol
appears in the status overview in the multi-
function display.
Vehicles with a colour multifunction dis-
play: when the distance warning function is
deactivated, the æ symbol appears in the
assistance graphics in the multifunction dis-
play.
The distance warning function can help you
to minimise the risk of a front-end collision
with a vehicle ahead or reduce the effects of
such a collision. If the distance warning func-
tion detects that there is a risk of a collision,
you will be warned visually and acoustically.
Without your intervention, the distance warn-
ing function cannot prevent a collision.
The distance warning function issues a warn-
ing at speeds:
R of around 30 km/h or more, if, over several
seconds, the distance maintained to the
vehicle travelling in front is insufficient. The
· distance warning lamp then lights up
in the instrument cluster.
R of around 7 km/h or higher, if you very
quickly approach a vehicle in front. An
intermittent warning tone will then sound, and the · distance warning lamp will
light up in the instrument cluster.
X Brake immediately in order to increase the
distance from the vehicle in front.
or
X Take evasive action provided it is safe to do
so.
Due to the nature of the system, particularly
complicated but non-critical driving condi-
tions

may also cause the system to display a
warning.
With the help of the radar sensor system, the
distance warning function can detect obsta-
cles that are in the path of your vehicle for an
extended period of time.
Up to a speed of around 70 km/h, the dis-
tance warning function can also react to sta-
tionary obstacles, such as stopped or parked
vehicles.
If you approach an obstacle and the distance
warning function detects a risk of a collision,
the system will alert you both visually and
acoustically.
In particular, the detection of obstacles can
be impaired in the case of:
R dirt on the sensors or obscured sensors
R snow or heavy rain
R interference by other radar sources
R strong radar reflections, for example, in
multi-storey car parks
R a narrow vehicle travelling in front, e.g. a
motorcycle
R a vehicle travelling in front on a different
line
Following damage to the front end of the vehi-
cle, have the configuration and operation of
the radar sensor checked at a qualified spe-
cialist workshop. This also applies to colli-
sions at slow speeds where there is no visible
damage to the front of the vehicle. Driving safety systems
63Safety Z

Adaptive Brake Assist
i
Observe the "Important safety notes" sec-
tion for driving safety systems
(Y page 61). G
WARNING
Adaptive Brake Assist cannot always clearly
identify objects and complex traffic situa-
tions. In these cases, Adaptive Brake Assist
may not intervene. There is a risk of an acci-
dent.
Always

pay careful attention to the traffic sit-
uation and be ready to brake. G
WARNING
Adaptive Brake Assist does not react:
R to people or animals
R to oncoming vehicles
R to crossing traffic
R to stationary obstacles
R when cornering
As a result, Adaptive Brake Assist may not
intervene in all critical conditions. There is a
risk of an accident.
Always

pay careful attention to the traffic sit-
uation and be ready to brake.
Adaptive Brake Assist aids you in braking dur-
ing hazardous situations at speeds above
30 km/h and uses the radar sensor system
to evaluate the traffic situation.
With the help of a sensor system, adaptive
Brake Assist can detect obstacles that are in
the path of your vehicle for an extended
period of time.
Should you approach an obstacle and adap-
tive Brake Assist has detected a risk of colli-
sion, adaptive Brake Assist calculates the
braking force necessary to avoid a collision.
Should you apply the brakes forcefully, adap-
tive Brake Assist will automatically increase
the braking force to a level suitable for the
traffic conditions. X
Keep the brake pedal depressed until the
emergency braking situation is over.
ABS prevents the wheels from locking.
The brakes will work normally again if:
R you release the brake pedal
R there

is no longer any danger of a collision
R no obstacle is detected in front of your
vehicle
Adaptive Brake Assist is then deactivated.
Vehicles with PRE-SAFE ®
: if adaptive Brake
Assist requires particularly high brake pres-
sure, preventative passenger protection
measures (PRE-SAFE ®
) are deployed simul-
taneously.
Up to vehicle speeds of around 250 km/h,
adaptive Brake Assist is capable of reacting
to moving objects that have already been rec-
ognised as such at least once over the period
of observation. Adaptive Brake Assist does
not react to stationary obstacles.
If adaptive Brake Assist is not available due
to a malfunction in the radar sensor system,
the brake system remains available with full
brake boosting effect and BAS.
In particular, the detection of obstacles can
be impaired if there is:
R dirt on the sensors or anything else cover-
ing the sensors
R snow or heavy rain
R interference by other radar sources
R the possibility of strong radar reflections,
for example, in multi-storey car parks
R a narrow vehicle travelling in front, e.g. a
motorcycle
R a vehicle travelling in front on a different
line
Following damage to the front end of the vehi-
cle, have the configuration and operation of
the radar sensor checked at a qualified spe-
cialist workshop. This also applies to colli-
sions at slow speeds where there is no visible
damage to the front of the vehicle. 64
Driving safety systems
Safety

Adaptive brake lamps
If you brake sharply from a speed of more
than
50 km/h or if braking is assisted by BAS
or adaptive Brake Assist, the brake lamps
flash rapidly. In this way, traffic travelling
behind you is warned in an even more notice-
able manner.
If you brake sharply from a speed of more
than 70 km/h to a standstill, the hazard warn-
ing lamps are activated automatically. If the
brakes are applied again, the brake lamps
light up continuously. The hazard warning
lamps switch off automatically if you travel
faster than 10 km/h. You can also switch off
the hazard warning lamps using the hazard
warning switch button (Y page 108).
i Adaptive brake lamps are only available in
certain countries. ESP
®
(Electronic Stability Program)
General notes i
Observe
the "Important safety notes" sec-
tion (Y page 61).
ESP ®
monitors driving stability and traction,
i.e. power transmission between the tyres
and the road surface.
If ESP ®
detects that the vehicle is deviating
from the direction desired by the driver, one
or more wheels are braked to stabilise the
vehicle. The engine output is also modified to
keep the vehicle on the desired course within
physical limits. ESP ®
assists the driver when
pulling away on wet or slippery roads. ESP ®
can also stabilise the vehicle during braking.
ETS/4ETS (Electronic Traction System) i
Observe
the "Important safety notes" sec-
tion (Y page 61).
ETS/4ETS traction control is part of ESP ®
.
ETS brakes the drive wheels individually if
they spin. This enables you to pull away and
accelerate on slippery surfaces, for example if the road surface is slippery on one side. In
addition, more drive torque is transferred to
the wheel or wheels with traction.
ETS remains active when you deactivate
ESP
®
.
Important safety notes G
WARNING
If ESP ®
is malfunctioning, ESP ®
is unable to
stabilise
the vehicle. In addition, other driving
safety systems are switched off. This increa-
ses the risk of skidding and an accident.
Drive on carefully. Have ESP ®
checked at a
qualified specialist workshop.
! When testing the electric parking brake
on a braking dynamometer, switch off the
ignition. Application of the brakes by
ESP ®
may otherwise destroy the brake sys-
tem.
! Vehicles with 4MATIC: switch off the igni-
tion when the electric parking brake is
being tested using a dynamometer.
Application of the brakes by ESP ®
may oth-
erwise destroy the brake system.
! Vehicles with 4MATIC: function or per-
formance tests may only be carried out on
a 2-axle dynamometer. Before operating
the vehicle on such a dynamometer, please
consult a qualified specialist workshop.
You could otherwise damage the drive train
or the brake system.
! Do not tow vehicles with 4MATIC with the
front or rear axle raised.
Vehicles without 4MATIC: when towing your
vehicle with the front axle raised, it is impor-
tant that you observe the notes on
ESP ®
(Y page 312).
Vehicles with 4MATIC: when towing your
vehicle with both axles on the ground, it is
important that you observe the notes on
ESP ®
(Y page 312). Driving safety systems
65
Safety Z

i
Activate ESP ®
as soon as the situations
described
above no longer apply. ESP ®
will
otherwise not be able to stabilise the vehi-
cle if the vehicle starts to skid or a wheel
starts to spin.
Deactivating/activating ESP ®X
To activate SPORT handling mode:
briefly press button :.
The M handling mode warning lamp in
the instrument cluster lights up. The
SPORT handling mode message appears
in the multifunction display.
X To deactivate SPORT handling mode:
briefly press button :.
The M handling mode warning lamp in
the instrument cluster goes out.
X To deactivate ESP ®
:
press button : until
the å ESP ®
OFF warning lamp lights up
in the instrument cluster.
The ÷OFF message appears in the mul-
tifunction display.
X To activate ESP ®
:
briefly press button :.
The å ESP ®
OFF warning lamp in the
instrument cluster goes out. The ÷
ESP ®
ON message appears in the multifunc-
tion display.
Characteristics of activated SPORT han-
dling mode
If

SPORT handling mode is activated and one
or more wheels start to spin, the ÷ ESP ®
warning lamp in the instrument cluster flashes. ESP
®
only stabilises the vehicle to a
limited degree.
When SPORT handling mode is activated:
R ESP ®
only improves driving stability to a
limited degree.
R traction control is still activated.
R engine torque is restricted to a limited
degree and the drive wheels are able to
spin.
The

spinning of the wheels results in a cut-
ting action for better traction on loose sur-
faces.
R ESP ®
still provides support when you
brake.
Characteristics when ESP ®
is deactivated
If ESP ®
is deactivated and one or more wheels
start to spin, the ÷ ESP®
warning lamp in
the instrument cluster does not flash. In such
situations, ESP ®
will not stabilise the vehicle.
If you deactivate ESP ®
:
R ESP ®
no longer improves driving stability.
R engine torque is no longer limited and the
drive wheels are able to spin.
The spinning of the wheels results in a cut-
ting action for better traction on loose sur-
faces.
R traction control is still activated.
R PRE-SAFE ®
is no longer available; nor is it
activated if you brake firmly with assis-
tance from ESP ®
.
R COLLISION PREVENTION ASSIST is no lon-
ger available; nor is it activated if you brake
firmly with assistance from ESP ®
.
R COLLISION PREVENTION ASSIST is no lon-
ger available; nor is it activated if you brake
firmly with assistance from ESP ®
.
R ESP ®
still provides support when you
brake. Driving safety systems
67
Safety Z

Deactivating/activating ESP
®
(except
AMG vehicles) Important safety notes
You can select between the following states
of ESP
®
:
R ESP ®
is activated.
R ESP ®
is deactivated. G
WARNING
If you deactivate ESP ®
, ESP ®
no longer sta-
bilises the vehicle. There is an increased risk
of skidding and an accident.
Only
deactivate ESP ®
in the situations descri-
bed in the following.
It may be best to deactivate ESP ®
in the fol-
lowing situations:
R when using snow chains
R in deep snow
R on sand or gravel
i Activate ESP ®
as soon as the situations
described above no longer apply. ESP ®
will
otherwise not be able to stabilise the vehi-
cle if the vehicle starts to skid or a wheel
starts to spin.
Deactivating/activating ESP ®
You can deactivate or activate ESP ®
via the
on-board computer.
X To deactivate: (Y page 218).
The å ESP ®
OFF warning lamp in the
instrument cluster lights up.
X To activate: (Y page 218).
The å ESP ®
OFF warning lamp in the
instrument cluster goes out.
Characteristics when ESP ®

is deactivated
If ESP ®
is deactivated and one or more wheels
start to spin, the ÷ ESP®
warning lamp in
the instrument cluster flashes. In such situa-
tions, ESP ®
will not stabilise the vehicle. If you deactivate ESP
®
:
R ESP ®
no longer improves driving stability.
R engine torque is no longer limited and the
drive wheels are able to spin.
The

spinning of the wheels results in a cut-
ting action for better traction on loose sur-
faces.
R traction control is still activated.
R ESP ®
still provides support when you
brake.
ESP ®
trailer stabilisation General notes
If your vehicle/trailer combination begins to
lurch, ESP
®
assists you in this situation.
ESP ®
slows the vehicle down by braking and
limiting the engine output until the vehicle/
trailer combination has stabilised.
Important safety notes G
WARNING
If road and weather conditions are poor,
trailer
stabilisation will not be able to prevent
the vehicle/trailer combination from swerv-
ing. Trailers with a high centre of gravity can
tip over before ESP ®
can detect this. There is
a risk of an accident.
Always adapt your driving style to the prevail-
ing road and weather conditions.
If your vehicle/trailer combination begins to
lurch, you can only stabilise the vehicle/
trailer combination by depressing the brake
firmly.
ESP ®
trailer stabilisation is active above
speeds of about 65 km/h.
ESP ®
trailer stabilisation does not work if
ESP ®
is deactivated or disabled because of a
malfunction. 68
Driving safety systems
Safety