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Driving and operating191Adaptive cruise control automatically
decelerates the vehicle when
approaching a slower moving vehicle.
It then adjusts the vehicle speed to
follow the vehicle ahead at the
selected following distance. The
vehicle speed increases or decreases to follow the vehicle in front, but willnot exceed the set speed. It may
apply limited braking with activated
brake lights.
To facilitate overtaking a vehicle on
the motorway, the activation of the
turn signal reduces the following
distance for a short time. This function is implemented only on the respective
driver's side depending on left or right
hand drive vehicle configuration.
The adaptive cruise control can store
set speed over 30 km/h for manual
transmission. On vehicles with
automatic transmissions the system
can brake until a full stop and drive off from a stop.
Adaptive cruise control uses radar
and camera sensors to detect the
vehicles ahead. If no vehicle is
detected in the driving path, the
adaptive cruise control will behave
like a conventional cruise control.
Adaptive cruise control is mainly
advised to be used on long straight
roads like highways or country roads
with steady traffic. Do not use the
system if it is not advisable to
maintain a constant speed.
Control indicator A 3 112, C 3 112.
9 Warning
The complete driver attention is
always required while driving with adaptive cruise control. The driver
stays fully in control of the vehicle
because the brake pedal, the
accelerator pedal and the cancel
switch have priority over any
adaptive cruise control operation.
Switching on
Illustrations show different versions.
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192Driving and operating
Press C to switch on adaptive cruise
control. C appears in the Driver
Information Centre.
Activation by setting the speedAdaptive cruise control can be
activated at speeds above 25 km/h on
vehicles with automatic transmission
or 30 km/h on vehicles with manual
transmission. The upper speed limit is 180 km/h.
Accelerate to the desired speed and
turn thumb wheel to SET/-, the
current speed is stored and
maintained.
The adaptive cruise control symbol
C , the following distance setting and
set speed are indicated in the Driver
Information Centre.
The accelerator pedal can be
released. Adaptive cruise control
remains activated during gear
shifting.
Overriding set speed
It is always possible to drive faster
than the selected set speed by
depressing the accelerator pedal.
When the accelerator pedal is
released, the vehicle returns to the
desired distance if a slower vehicle is ahead. Otherwise it returns to the
stored speed.
Once the system is activated,
adaptive cruise control decelerates or
brakes if it detects a vehicle ahead,
which is slower or closer than the
desired following distance.9 Warning
Accelerating by the driver
deactivates automatic braking by
the system. This is indicated as a
pop-up warning in the Driver
Information Centre or by the
adaptive cruise control symbol
turning blue.
Take over current speed
If the accelerator pedal is pressed,
the current vehicle speed is taken
over as stored speed. This is also
valid, if the current vehicle speed is
lower than the Set Speed.
Increase speed
With adaptive cruise control active,
hold RES/+ to increase speed
continuously. Push RES/+ repeatedly
to increase speed in small
increments.
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Driving and operating193Reduce speedWith adaptive cruise control active,
hold SET/- to decrease speed
continuously. Push SET/- repeatedly
to decrease speed in small
increments.
Resume stored speed
If a speed was stored before and system is switched on but inactive,
turn thumb wheel to RES/+ at a speed
above 5 km/h (with Automatic
Transmission) or above 30 km/h (with
manual transmission) to resume the
stored speed.
Full speed range adaptive cruise
control on vehicles with automatic transmission
Full speed range adaptive cruise
control will maintain a following
distance behind a detected vehicle
and slow your vehicle to a stop behind
that vehicle.
When the vehicle ahead accelerates
after a brief stop, the adaptive cruise
control will drive off automatically
without driver action. If necessary,press RES/+ or the accelerator pedal
to resume adaptive cruise control.
Pressing the accelerator pedal allows
more control over the acceleration
after driving off. Note that automatic
braking is disabled during usage of
the accelerator pedal.
If the stopped vehicle ahead stands
for a longer time and then begins to
move forward, the green illuminated
vehicle ahead control indicator A will
flash and a warning chime will sound
as a reminder to check traffic before
resuming.9 Warning
When full speed range adaptive
cruise control is deactivated or
cancelled, the vehicle will no
longer be held at a stop and can
start moving. Always be prepared
to manually apply the brake pedal
to hold the vehicle stationary.
Do not leave the vehicle while it is being held at a stop by the full
speed range adaptive cruise
control. Always move selector
lever to park position P and switch
off the ignition before leaving the
vehicle.
Setting the following distance
When adaptive cruise control detects a slower moving vehicle in the drivingpath, it will adjust the vehicle speed to
maintain the following distance
selected by the driver.
The following distance can be set to
near, medium or far.
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194Driving and operatingPress E, the current setting is shown
in the Driver Information Centre.
Press E again to change the
following distance. The setting is also displayed in the Driver Information
Centre.
The selected following distance is
indicated by filled distance bars in the
adaptive cruise control page.
Note that the following distance
setting is shared with the sensitivity
setting of forward collision alert
3 198.
Example: If setting 3 (far) is selected,
then the driver is warned sooner
before a possible collision, also if
adaptive cruise control is inactive or
switched off.9 Warning
The Driver accepts full
responsibility to drive with the
appropriate following distance
based on traffic, weather, visibility
and regional regulation. Followingdistance must be adjusted or the
system switched off when required by the prevailing conditions.
Adaptive cruise control in Sport
mode
On vehicles with Flex Ride driving
modes, the driver can slightly
increase the Adaptive cruise control
acceleration when Sport mode is
selected. This function can be
deactivated in the Flex Ride
visualisation menu 3 184
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Driving and operating195Detecting the vehicle ahead
The green illuminated vehicle ahead
control indicator A is displayed when
the system detects a vehicle in the driving path. The range of the sensors
is between 25 and 150 metres
depending on vehicle speed.
Forward collision alert 3 198.
If this symbol does not display, or
displays briefly, adaptive cruise
control will not respond to vehicles ahead.
Deactivation Adaptive cruise control is deactivatedby the driver when:
● y is pressed.
● Brake pedal is applied.
● Clutch pedal is depressed for more than four seconds.
● Selector lever of automatic transmission is moved to N.
The system is also automatically deactivated when:
● Vehicle speed accelerates above
190 km/h or slows down below
25 km/h, on vehicles with
automatic transmission it slows
down to a stop without
deactivating within five minutes.
● The Traction Control system is deactivated or operating.
● The Electronic Stability Control is
deactivated or operating.
● There is no traffic and nothing detected on the road sides forapprox. one minute. In this casethere are no radar echoes and
the sensor may report that it is
blocked.
● The active emergency braking system is applying the brakes.
● Driving on steep inclines.
● The radar sensor is blocked by an ice or water film.● A fault is detected in the radar,camera, engine or brake system.
● The brakes need to cool down.
Additionally, the system is
automatically deactivated on vehicles
with automatic transmission (full
speed range adaptive cruise control)
when:
● The incline uphill or downhill is greater than 20 %.
● The electric parking brake is applied.
● The vehicle is being held to a stop
by the system for more than
five minutes.
● The vehicle stops, the driver's seat belt is unbuckled and thedriver's door is opened.
When adaptive cruise control is
deactivated, the control indicator m
changes from green to white and a
pop-up message is displayed in the
Driver Information Centre.
The stored speed is maintained.
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196Driving and operating
On Midlevel display, the stored speedis indicated in brackets in the Driver
Information Centre when the system
is deactivated but not switched off.
On Uplevel display, the adaptive
cruise control symbol C changes
from green to white when the system
is deactivated but not switched off.
9 Warning
When adaptive cruise control is
deactivated, the driver must take
over full brake and engine control
immediately.
Switching off
Press C to switch off adaptive cruise
control. The control indicator C in the
Driver Information Centre
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 needs 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 of the vehicle.
● 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 limits9 Warning
The system's automatic brake
force does not permit hard braking and the braking level may not be
sufficient to avoid a collision.
● After a sudden lane change, the system needs a certain time to
detect 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 consider pedestrians and
animals for braking and driving
off.
● Adaptive cruise control considers
stopped vehicles only at low
speed.
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Driving and operating197● Do not use adaptive cruisecontrol when towing a trailer.
● Do not use adaptive cruise control on roads with an incline ofmore than 10%.
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. The
camera applies a certain correction
based on the detectable lane
markings. The control indicator A will
extinguish, if a vehicle ahead is no longer detected.
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. Furthermore,
Adaptive cruise control was designed to brake as late as possible to allow
changing the lane before the
automatic braking. 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 while
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.
Page 200 of 323

198Driving and operatingHill and trailer considerations9Warning
Do not use adaptive cruise control
on steep hill roads.
System performance on hills depends
on vehicle speed, vehicle load, traffic
conditions and the road gradient. It
may not detect a vehicle in your path
while driving on hills. Full speed range
adaptive control is deactivated
automatically, as the vehicle is
stopping uphill on an incline greater than 10%. In this condition, be
prepared to take control of the
vehicle.
Note that applying the brake
deactivates the system.
Radar unit
The radar unit is mounted behind the
radiator grille behind or below the
brand emblem.
9 Warning
The radar unit was aligned
carefully during manufacture.
Therefore, in the event of a front-
end impact, 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 adjust the radar unit
position.
Settings
Settings can be changed in the
vehicle personalisation menu in the
Info-Display.
Select the relevant setting in Settings,
I Vehicle in the Info-Display.
Info-Display 3 120.
Vehicle personalisation 3 126.
Fault
If the adaptive cruise control does not
work due to temporary conditions
(e.g. blockage by ice, overheated
brakes or low speed manoeuvres) or
if there is a permanent system error,
a message is displayed in the Driver
Information Centre.
Vehicle messages 3 124.
Forward collision alert The forward collision alert may help toavoid or reduce the harm caused by
front-end crashes.