
Seat belts
148
The physical principle of a frontal 
collision
The physical principle of a frontal accident can be explained quite simply: Motion energy, so-called kinetic energy, is produced as soon as the 
vehicle is moving, both for the vehicle and its occupants. The magnitude 
of this kinetic energy depends essentially on the speed at which the 
vehicle is travelling and on the weight of the vehicle and the occupants. 
The greater the speed and weight increase, the greater the amount of 
energy which has to be absorbed in the event of an accident.
The speed of the vehicle is, nevertheless, the most important factor. 
Doubling the speed of the vehicle from 25 km/h up to 50 km/hour 
increases the kinetic energy four times.
The common opinion that it is possible to support your body in a minor 
accident with your hands, is incorrect. Even in a collision at only a low 
speed, the forces acting on the body are such that it is no longer possible 
to support your body.
Even if you only drive at a speed within the range from 30 km/hour to 50 
km/hour, the forces which are produced on your body in the event of an 
accident can easily exceed 10.000 N (Newton). This equals a weight of 
one tonne (1 000 kg).
In the event of a frontal collision, occupants of the car not wearing a seat 
belt, are thrown forward and strike in an uncontrolled way parts of the inte-
rior of the car, such as steering wheel, dash panel, windscreen, 
⇒fig. 119 . 
The occupants of a vehicle who have not fastened their seat belts may 
even be thrown out of the vehicle. This can result in fatal injuries.
It is also important that rear seat occupants fasten their seat belts as they 
will otherwise be thrown through the vehicle in an uncontrolled manner in 
the event of an accident A rear seat passenger who has not fastened the 
seat belt is a danger not only to himself but also for those seated at the 
front  ⇒fig. 120 .
Fig. 119  The driver is 
thrown forward if not 
wearing a belt
Fig. 120  The rear seat 
occupant is thrown 
forward if not wearing a 
belt
NKO 20 A05.book  Page 148  Wednesday, June 21, 2006  1:42 PM 

Intelligent Technology
178
The ESP warning light  ⇒page 35 lights up in the instrument cluster when 
there is a fault on the ESP.
Switching off
You can switch the ESP off and on again as you wish, by pressing the 
button  ⇒page 177, fig. 145 . The ESP warning light  ⇒page 35 lights up 
in the instrument cluster when the ESP is switched off.
The ESP should normally always be switched on. It may be good practice 
in certain exceptional cases, such as when you wish to have wheel slip, 
to switch off the system.
Examples:
•when driving with snow chains,
•when driving in deep snow or on a loose surface,
•when it is necessary to rock a car free when it has become stuck.
Then you should switch on the ESP again.
WARNING
It is also not possible for the E SP to overcome the physical limits 
of the vehicle. Even if a vehicle fitted with ESP you should still 
always adapt your style of driving to the condition of the road 
surface and the traffic situation. This particularly applies when 
driving on slippery and wet roads. The increased safety offered 
must not tempt you to take greater risks than otherwise - risk of an 
accident!
Note
•All four wheels must be fitted with the same tyres in order to achieve 
problem-free operation of the ESP. Differing rolling circumferences of the 
tyres can lead to an undesirable reduction in the engine output.
•Changes to vehicle (e.g. on engine, on the brakes, on chassis or other 
assignment of tyres and wheels) can influence the function of the ESP 
⇒ page 232, “Accessories, changes and replacement of parts”.
Traction control system (TCS)*
The traction control system prevents the driven wheels 
from spinning when accelerating.
General
The TCS makes it much easier, and sometimes at all possible, to start off, 
accelerate and climb a steep hill when the conditions of the road surface 
are unfavourable.
Operating principle
The TCS switches on automatically when the engine is started and then 
conducts a self-test. The system monitors the speeds of the driven wheels 
with the aid of the ABS sensors. If the wheels are spinning, the force trans-
Fig. 146  TCS switch
NKO 20 A05.book  Page 178  Wednesday, June 21, 2006  1:42 PM 

Intelligent Technology179
Using the systemSafetyDriving TipsGeneral MaintenanceBreakdown assistanceTechnical Data
mitted to the road surface is automatically adapted by reducing the engine 
speed. This occurs at all speeds.
The TCS operates in combination with the ABS 
⇒page 181, “Antilock 
brake system (ABS)*”. The TCS will not f unction if a fault exists in the ABS 
system.
The TCS warning light  ⇒page 34 lights up in the instrument cluster when 
there is a fault on the TCS.
Switching off
You can switch the TCS off and on again as you wish by pressing the 
button  ⇒page 178, fig. 146 . The TCS warning light  ⇒page 34 lights up 
in the instrument cluster when the TCS is switched off.
The TCS should normally always be switched on. It may be good practice 
in certain exceptional cases, such as when you wish to have wheel slip, 
to switch off the system.
Examples:
•when driving with snow chains,
•when driving in deep snow or on a loose surface,
•when it is necessary to rock a car free when it has become stuck.
then you should switch on the TCS again.
WARNING
You should always adjust your style of driving to the conditions of 
the road surface and the traffic situation. The increased safety 
offered must not tempt you to take greater risks than otherwise - 
risk of an accident!
Note
•All four wheels must be fitted with the same tyres in order to achieve 
problem-free operation of the TCS. Differing rolling circumferences of the 
tyres can lead to an undesirable reduction in the engine output.
•Changes to vehicle (e.g. on engine, on the brakes, on chassis or other 
assignment of tyres and wheels) can influence the function of the TCS 
⇒ page 232, “Accessories, changes and replacement of parts”.
Electronic Differential Lock (EDL)*
The electronic differential lock prevents an individual 
wheel from slipping.
Models fitted with ESP are equipped with electronic differential lock (EDL).
General
The EDL makes it much easier, and sometimes at all possible, to start off, 
accelerate and climb a steep hill when the conditions of the road surface 
are unfavourable.
Operating principle
The EDL is activated automatically, that is without any action on the part 
of the driver. It monitors the speeds of the driven wheels with the aid of the 
ABS sensors. Should only  one drive wheel begin spinning on a slippery 
surface there will be an appreciable difference in the speed of the driven 
wheels. The EDL function brakes the slipping wheel and the differential 
transmits a greater driving force to the other driven wheel. This control 
process is also accompanied by noises.
Overheating of the brakes
The EDL switches off automatically if unusually severe stresses exist in 
order to avoid excessive heat generation in the disc brake on the wheel 
NKO 20 A05.book  Page 179  Wednesday, June 21, 2006  1:42 PM