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Driving and operating175
maintained. Control indicator m or
C in the instrument cluster
illuminates green.
The adaptive cruise control symbol,
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 while gearshifting.
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 braking by the system. This is indicated as a popup
warning in the Driver Information
centre.
Increase speed
With adaptive cruise control active,
hold thumb wheel turned to RES/+: speed increases continuously in large increments, or activate repeatedly
RES/+: speed increases in small
increments.
If the vehicle is driven with adaptive cruise control active much faster than
the desired speed, e.g. after
depressing the accelerator pedal,
then the current speed can be stored and maintained by turning the thumb
wheel to SET/-.
Reduce speed
With adaptive cruise control active,
hold thumb wheel turned to SET/-:
speed decreases continuously in
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176Driving and operating
large increments, or activate
repeatedly SET/-: speed decreases in small increments.
If the vehicle is driven with adaptive
cruise control active much slower
than the desired speed, e.g. because
of a slower vehicle ahead, then the
current speed can be stored and
maintained by turning the thumb
wheel to SET/-.
Resume stored speed
If the system is switched on but
inactive, then turn thumb wheel to
RES/+ at a speed above 25 km/h to
resume the stored speed.
Full speed range adaptivecruise control on vehicles withautomatic transmission Full speed range adaptive cruise
control will maintain a following gap
behind a detected vehicle and slow
your vehicle to a stop behind that
vehicle.When the vehicle ahead drives away
within two minutes, turn thumb wheel
to RES/+ or operate the accelerator
pedal to resume full speed range
adaptive cruise control.
If the stopped vehicle ahead begins to move forward and full speed range
adaptive cruise control has not
resumed, the green illuminated
vehicle ahead control indicator A will
flash and a warning chime will sound
as a reminder that the vehicle ahead
is pulling away.
When the vehicle ahead stops for
more than two minutes, the electric
parking brake will apply automatically and the full speed range adaptive
cruise control is deactivated. In this
event, drive the vehicle normally by
operating the accelerator pedal. Turn
thumb wheel to RES/+ at a speed
above 25 km/h to resume full speed
range adaptive cruise control.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 to move. Always be prepared to manually apply the brake 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 driving path, it will adjust the vehicle speed tomaintain the following distance
selected by the driver.
The following distance can be set to
near, medium or far.
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Driving and operating177
Press button E, the current setting is
shown in the Driver Information
Centre. Press button 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
3 181.
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 for the appropriate
following distance based on traffic, weather and visibility conditions.
Following distance must be
adjusted or the system switched
off when required by the prevailing
conditions.
Detecting the vehicle ahead
The green illuminated vehicle ahead
control indicator A is displayed when
the system detects a vehicle in the driving path.
If this symbol does not display, or
displays briefly, adaptive cruise
control will not respond to vehicles
ahead.
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178Driving and operating
Deactivation
Adaptive cruise control is deactivated by the driver when:
■ button y is pressed,
■ brake pedal is applied,
■ clutch pedal is depressed for more than four seconds,
■ gear 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 below15 km/h (on vehicles with automatic transmission it slows down to a stop
without deactivating within
two minutes),
■ Traction Control system is operating for more than
20 seconds,
■ Electronic Stability Control is operating,■ 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,
■ collision imminent braking is applying the brakes,
■ radar sensor is blocked by an ice or
water film,
■ fault is detected in the radar, engine
or brake system.
Additionally the system is
automatically deactivated on vehicles with automatic transmission (full
speed range adaptive cruise control)
when:
■ Electric parking brake is applied,
■ vehicle is being held to a stop by the
system for more than two minutes,
■ vehicle stops and a door is opened.
When adaptive cruise control is
deactivated automatically, the control indicator m or C 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 button C to switch off adaptive
cruise control. The control indicator
m or C extinguishes. The stored
speed is deleted.
Switching off the ignition also
switches off adaptive cruise control
and deletes the stored speed.
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Driving and operating179
Driver's attention■ Use adaptive cruise control carefully on bends or mountainroads, 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 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 completelythe 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.
■ 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 brake for pedestrians, animals or
stopped vehicles.
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
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180Driving and operating
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 press the brake
pedal, if you need to brake more
quickly.
Hill and trailer considerations
System performance on hills and
when towing a trailer 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. 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,
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Driving and operating181consult a workshop to verify and
correct the adaptive cruise control sensor position.
Settings
Settings can be changed in the
vehicle personalisation menu in the
Colour-Info-Display.
Select the relevant setting in Settings,
I Vehicle in the Colour-Info-Display.
Colour-Info-Display 3 114.
Vehicle personalisation 3 118.
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.
Vehicle messages 3 116.
Forward collision alert
The forward collision alert can help to
avoid or reduce the harm caused by
front-end crashes. If a vehicle directly
ahead is approached too quickly, a
warning chime and alert in the Driver
Information Centre is provided.
The green illuminated vehicle ahead
symbol A appears in the instrument
cluster when the system has detected
a vehicle in the driving path. A
precondition is that forward collision
alert is activated in the vehicle
personalisation menu 3 118 or that it
is not deactivated by the button V
(depending on the system, see
below).
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 3 173.
■ Forward collision alert based on
front camera system
on vehicles with no cruise control or
traditional cruise control only
3 171.
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182Driving and operating
Forward collision alert based onradar systemThe system uses the radar sensor
behind the radiator grille to detect a
vehicle directly ahead, in your path,
within a distance of max. 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
3 118.
Selecting the alert sensitivity
The alert sensitivity can be set to
near, medium or far.
Press button E, the current setting is
shown in the Driver Information
Centre. Press button E again to
change the alert sensitivity. The
setting is also displayed in the Driver Information Centre.Note that the alert timing sensitivity
setting is shared with the following
distance setting of the adaptive cruise
control 3 173. So changing the alert
timing sensitivity changes the
adaptive cruise control following
distance setting.
Alerting the driver