DRIVER SUPPORT
* Option/accessory.
234
Collision warning system* -
limitations
The function has certain limitations - for example,
it is not active until 4 km/h (3 mph).
The collision warning system's visual warning sig-
nal may be difficult to notice in the event of
strong sunlight, reflections, when sunglasses are
being worn or if the driver is not looking straight
ahead. The warning sound should therefore
always be activated.
On slippery road surfaces the braking distance is
extended, which may reduce the capacity to avoid
a collision. In such situations the ABS and ESC
(p. 186) systems will provide best possible brak-
ing force with maintained stability.
NOTE
The visual warning signal can be temporarily
disengaged in the event of high passenger
compartment temperature caused by strong
sunlight for example. If this occurs then the
warning sound is activated even if it is deacti-
vated in the menu system.
•Warnings may not appear if the distance
to the vehicle in front is small or if steer-
ing wheel and pedal movements are
large, e.g. a very active driving style.
WARNING
Warnings and brake interventions could be
implemented late or not at all if the traffic sit-
uation or external influences mean that the
radar or camera sensor cannot detect a
pedestrian, a vehicle or a cyclist in front cor-
rectly.
The sensor system has a limited range for
pedestrians and cyclists25 - the system can
give effective warnings and brake interven-
tions for them at vehicle speeds up to
50 km/h (30 mph). For stationary or slow-
moving vehicles, warnings and brake interven-
tions are effective at vehicle speeds up to
70 km/h (43 mph).
Warnings for stationary or slow-moving vehi-
cles could be disengaged due to darkness or
poor visibility.
Warnings and brake interventions for pedes-
trians and cyclists are deactivated at vehicle
speeds exceeding 80 km/h (50 mph).
The collision warning system uses the same
radar sensors as the adaptive cruise control
(p. 203).
If warnings are perceived as being too frequent
or disturbing then the warning distance can be
reduced. This then leads to the system providing
a warning at a later stage, which reduces the
total number of warnings; see Collision warning
system - operation (p. 232).
Collision Warning with Auto Brake is temporarily
deactivated with reverse gear engaged.
Collision Warning with Auto Brake is not acti-
vated at low speeds - below 4 km/h (3 mph),
which is why the system does not intervene in sit-
uations where the car is approaching a vehicle in
front very slowly, e.g. when parking.
In situations where the driver demonstrates
active, aware driving behaviour, a collision warn-
ing may be postponed slightly in order to keep
unnecessary warnings to a minimum.
When Auto Brake has prevented a collision with
a stationary object the car remains stationary for
a maximum of 1.5 seconds. If the car is braked
for a vehicle in front that is moving, then speed is
reduced to the same speed as that maintained by
the vehicle in front.
On a car with manual gearbox the engine stops
when Auto Brake has stopped the car, unless the
driver manages to depress the clutch pedal
beforehand.
Related information
•Collision warning system* (p. 228)
25 For cyclists, the warning and full brake intervention may come very late or simultaneously.
