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Driving and operating167● There is no traffic and nothingdetected on the road sides for
several minutes. In this case,
there are no radar echoes and
the sensor may report that it is
blocked.
● The collision imminent braking system is applying the brakes.
● The radar sensor is blocked by an ice or water film.
● A fault is detected in the radar, engine or brake system.
When adaptive cruise control is
deactivated automatically, the control
indicator m illuminates white and a
warning symbol is displayed as a pop- up in the Driver Information Centre.
The stored speed is maintained.
9 Warning
When adaptive cruise control is
deactivated, the driver must take
over full brake and engine control.
Switching off
Press C to switch off adaptive cruise
control. The control indicator m
extinguishes. The stored speed is
deleted.
Switching off the ignition also
switches off adaptive cruise control
and deletes the stored speed.
Driver's attention
● Use adaptive cruise control carefully on bends or mountain
roads, as it can lose the vehicle
ahead and need time to detect it
again.
● Do not use the system on slippery roads as it can create
rapid changes in tyre traction
(wheel spinning), so that you
could lose control.
● Do not use adaptive cruise control during rain, snow or
heavy dirt, as the radar sensor
can be covered by a water film,
dust, ice or snow. This reduces or suppresses completely the
visibility. In case of sensor
blockage, clean the sensor
cover.
System limits ● The system's automatic brake force does not permit hard
braking and the braking level
may not be sufficient to avoid a
collision.
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168Driving and operating● After a sudden lane change, thesystem needs a certain time todetect the next preceding
vehicle. So if a new vehicle is
detected, the system may
accelerate instead of braking.
● Adaptive cruise control does ignore the oncoming traffic.
● Adaptive cruise control does not brake for stopped vehicles,
pedestrians or animals.
Bends
The adaptive cruise control calculates
a predicted path based on the
centrifugal force. This predicted path
considers the current bend
characteristic, but cannot consider a
future bend change. The system may lose the current vehicle ahead or
consider a vehicle which is not in the
actual lane. This can happen when
entering or exiting a bend or if the
bend gets stronger or weaker. If it no
longer detects any vehicle ahead,
then control indicator A will
extinguish.
If the centrifugal force is too high in a bend, the system slows down the vehicle slightly. This braking level is
not designed to avoid spinning off the bend. The driver is responsible for
reducing the selected speed before
entering a bend and in general to
adapt the speed to the road type and
to existing speed limits.
Motorways
On motorways, adapt the set speed
to the situation and the weather.
Always consider that adaptive cruise
control has a limited visibility range, a
limited braking level and a certain
reaction time to verify if a vehicle is on
the driving path or not. Adaptive
cruise control may not be able to
brake the vehicle in time to avoid a
collision with a much slower vehicle or after a lane change. This is
particularly true if driving fast or if the
visibility is reduced due to weather
conditions.
While entering or exiting a motorway,
adaptive cruise control may lose the
vehicle ahead and accelerate up to
the set speed. For this reason,
decrease the set speed before the
exit or before the entry.
Vehicle path changes
If another vehicle enters your driving
path, adaptive cruise control will first
consider the vehicle when it is
completely in your path. Be ready to
take action and depress the brake
pedal, if you need to brake more
quickly.
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Driving and operating169Hill and trailer considerations
System performance on hills and
when towing a trailer depends on your
vehicle speed, vehicle load, traffic
conditions and the road gradient. It
may not detect a vehicle in your path
while driving on hills. On steep hills,
you may have to use the accelerator
pedal to maintain your vehicle speed. When going downhill, especially
when towing a trailer, you may have
to brake to maintain or reduce your
speed.
Note that applying the brake
deactivates the system. It is not
recommended to use adaptive cruise
control on steep hills especially when towing a trailer.
Radar unit
The radar unit is mounted behind the
radiator grille below the brand
emblem.
9 Warning
The radar unit was aligned
carefully during manufacture.
Therefore, after a frontal accident, do not use the system. The front
bumper may appear to be intact,
however the sensor behind can be
out of position and react
incorrectly. After an accident,
consult a workshop to verify and
correct the adaptive cruise control
sensor position.
Settings
Settings can be changed in the Auto
collision preparation menu in the
vehicle personalisation, 3 106.
Fault
If the adaptive cruise control does not
work due to temporary conditions
(e.g. blockage by ice) or if there is a
permanent system error, then a
message is displayed in the Driver
Information Centre.
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170Driving and operatingVehicle messages 3 100.
Forward collision alert The forward collision alert can help to
avoid or reduce the harm caused by
front-end crashes.
A vehicle ahead is indicated by a
control indicator A.
If a vehicle directly ahead is
approached too quickly, a warning
chime and alert in the Driver
Information Centre is provided.
A precondition is that forward collision
alert is activated in the vehicle
personalisation menu 3 106 or that it
is not deactivated by pressing V
(depending on the system, see
following).
Depending on the vehicle's
equipment, there are two variants of
the forward collision alert available:
● Forward collision alert based on
radar system
on vehicles equipped with
adaptive cruise control 3 163.
● Forward collision alert based on
front camera system
on vehicles with traditional cruise
control or none 3 160.
Forward collision alert based on
radar system
The system uses the radar sensor
behind the radiator grille to detect a
vehicle directly ahead, in your path,
within a maximum distance of
150 metres.
Activation
Forward collision alert operates
automatically above walking speed,
provided that Auto collision
preparation setting is not deactivated
in the vehicle personalisation menu
3 106.
Selecting the alert sensitivity
The alert sensitivity can be set to
near, medium or far.
Page 173 of 295
Driving and operating171
Press E; the current setting is shown
in the Driver Information Centre.
Press E again to change the alert
sensitivity. The setting is also displayed in the top line of the Driver
Information Centre.Note that the alert timing sensitivity
setting is shared with the following
distance setting of the adaptive cruise control. So changing the alert timing
sensitivity changes the adaptive
cruise control following distance
setting.
Alerting the driver
A green illuminated vehicle ahead
control indicator A illuminates in the
instrument cluster when the system has detected a vehicle in the driving
path. When the distance to a
preceding moving vehicle gets too
small or when approaching another
vehicle too rapidly and a collision is
imminent, the collision alert symbol
pops-up in the Driver Information
Centre. Simultaneously a warning
chime sounds.
Depress the brake pedal, if it is
required by the situation.
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172Driving and operatingSettings
Settings can be changed in the Auto
collision preparation menu in the
vehicle personalisation 3 106.
Forward collision alert based on
front camera system
Forward collision alert uses the front
camera system in the windscreen to
detect a vehicle directly ahead, in
your path, within a distance of approx. 60 metres.
Activation
Forward collision alert operates
automatically above 40 km/h, if it is
not deactivated by pressing V, see
below.
Selecting the alert sensitivity
The alert sensitivity can be set to
near, medium or far.
Press V; the current setting is shown
in the Driver Information Centre.
Press V again to change the alert
sensitivity.
Alerting the driver
A green illuminated vehicle ahead
control indicator A illuminates in the
instrument cluster when the system has detected a vehicle in the driving
path.
When the distance to a preceding
moving vehicle gets too small or when
approaching another vehicle too
rapidly and a collision is imminent, the
collision alert symbol pops-up in the
Driver Information Centre.
Simultaneously a warning chime
sounds. Depress the brake pedal, if it is required by the situation.
Page 175 of 295

Driving and operating173Deactivation
The system can be deactivated.
Press V repeatedly until the following
message appears in the Driver
Information Centre.
General information for both
variants of forward collision alert
9 Warning
Forward collision alert is just a
warning system and does not
apply the brakes. When
approaching a vehicle ahead too
rapidly, it may not provide you
enough time to avoid a collision.
The driver accepts full
responsibility for the appropriate
following distance based on traffic, weather and visibility conditions.
The complete attention of the
driver is always required while
driving. The driver must always be
ready to take action and apply the
brakes.
System limitations
The system is designed to warn only for vehicles, but may react also to
other metallic objects.
In the following cases, forward
collision alert may not detect a vehicle ahead or sensor performance is
limited:
● on winding roads
● when weather limits visibility, e.g.
fog, rain, or snow
● when the sensor is blocked by snow, ice, slush, mud, dirt, or
windscreen damage
Following distance
indication
The following distance indication
displays the distance to a preceding
moving vehicle. The system uses,
depending on the vehicle equipment,
either the radar behind the radiator
grille or the front camera in the
windscreen to detect the distance of
a vehicle directly ahead in your path.
It is active at speeds above 40 km/h.
When a preceding vehicle is detected
ahead, the distance is indicated in
seconds, displayed on a page in the
Driver Information Centre 3 94 . Press
MENU on the turn signal lever to
select Vehicle Information Menu
X and turn the adjuster wheel to
choose following distance indication
page.
Page 176 of 295

174Driving and operating
The minimum indicated distance is
0.5 s.
If there is no vehicle ahead or the vehicle ahead is out of range, two
dashes will be displayed: -.- s.
Active Emergency Braking
Active emergency braking can help to reduce the damage from crashes with vehicles and obstacles directly
ahead, when a collision can no longer be avoided either by manual braking
or by steering. Before the active
emergency braking applies, the driver
is warned by the forward collision
alert 3 170.
The feature uses various inputs (e.g.
radar sensor, brake pressure, vehicle speed) to calculate the probability of
a frontal collision.
Active emergency braking operates automatically above walking speed,
provided that Auto collision
preparation setting is not deactivated
in the vehicle personalisation menu
3 106.
The system includes: ● brake preparation system
● emergency automatic braking
● forward looking brake assist9Warning
This system is not intended to
replace the driver responsibility of driving the vehicle and looking
ahead. Its function is limited to
supplemental use only. The driver shall continue to apply the brake
pedal as the driving situation
dictates.
Brake preparation system
When approaching a vehicle ahead
so quickly that a collision is likely, the
brake preparation system slightly
pressurises the brakes. This reduces
the response time, when a manual or automatic braking is requested.
The brake system is prepared so that braking can occur more rapidly.
Emergency automatic braking
After the brake preparation and just
before the imminent collision, this
function automatically applies limited
braking to reduce the impact speed of the collision.
Forward looking brake assist
In addition to brake preparation
system and emergency automatic
braking, the forward looking brake
assist function makes the brake assist more sensitive. In this way,
depressing the brake pedal slightly
results immediately in a strong
braking. This function helps the driver
brake quicker and stronger before the imminent collision.