System functions

The following system functions of the multiple restraint system (MRS) are described:

• Triggering the multiple restraint system
• Visual and audible seat-belt warning

  Triggering the multiple restraint system 

  Extensive testing has allowed the triggering thresholds to be determined for all possible types of accidents.

  The following triggering thresholds were set for activating the different restraint systems:

  • Seat-belt tensioner
  • Front airbags
  • Side airbags and head-level airbags
  • Safety battery terminal
  • Electric fuel pump

The following examples illustrate how the various restraint systems are triggered:

• Head-on collision 

  The belt tensioner and the front airbags are activated if frontal impact is sufficient to exceed the triggering thresholds in the MRS control unit.

  The belt tensioners have a lower triggering threshold than the front airbags. This means that depending on accident severity, only the belt tensioner may be activated by the MRS control unit.

  If the seat-belt buckle switch is faulty, the MRS control unit will attempt to activate the belt tensioner in spite of the error message.

  If the seat-occupancy detector is faulty, the control unit assumes that the passenger seat is not  occupied. The restraint systems are not activated. Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.

• Side impact 

  If the triggering threshold in the MRS control unit is exceeded, the side airbag and the head-level airbag on the side affected by the impact are activated. Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.

• Front diagonal impact 

  The airbags and belt tensioners are triggered depending on the rate of vehicle deceleration in a longitudinal or lateral direction.

  If several triggering thresholds are exceeded, the corresponding restraint systems will be triggered for frontal collision and/or side impact (front airbag, side airbag, head-level airbag).

  Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.

• Rear-end collision 

  The belt tensioners are activated if rear impact is sufficient to exceed the triggering threshold in the MRS control unit.

  Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.

• Rear diagonal impact 

  The airbags (side airbags, head-level airbags) and belt tensioners are triggered depending on the rate of vehicle deceleration (or acceleration). If a number of triggering thresholds are exceeded, the appropriate restraint systems are activated.

  Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.

• Rollover 

  The MRS control unit does not detect the vehicle rolling over.

  The corresponding restraint systems are triggered: for example if the side impact causes the vehicle to roll over or if impact occurs while the vehicle is rolling over and the operating thresholds in the MRS control unit are exceeded.

  Depending on accident severity, the safety battery terminal is activated and the electric fuel pump switched off.

  Visual and audible seat-belt warning 

  For the seat-belt warning, the signals of the 2 seat-belt buckle switches (driver's belt/front-passenger belt) are monitored separately.

  If the seat occupancy detector detects that the passenger seat is occupied, the passenger belt must be inserted into the seat belt buckle. This switches off the seat-belt warning.

  The following situations are taken into account in respect of the issuing of a seat-belt warning:

• Front seat belt not fastened and distance driven less than 200 m 
  • Driver's side only:

    If the distance driven is less than 200 m, only the seat-belt warning lamp lights up. The vehicle may for example be driven out of a garage without triggering an acoustic seat-belt warning.

• Front seat belt not fastened and distance driven more than 200 m 

  The seat-belt warning lamps lights up. The acoustic seat-belt warning is activated for approximately 90 seconds.

  Once the seat belt has been fastened, the seat-belt warning lamp goes out. The acoustic seat-belt warning is deactivated.

  • Driver's side:

    If the seat belt has not  been fastened by the end of the acoustic seat-belt warning, the seat-belt warning lamp will stay on.

  • Passenger side:

    If the seat belt has not  been fastened by the end of the acoustic seat-belt warning, the seat-belt warning lamp and the acoustic seat-belt warning are deactivated.

• Unfastening the front seat belt when the vehicle is in motion 
  • Driver's side:

    The seat-belt warning lamps lights up immediately.

    After approx. 15 seconds an acoustic seat-belt warning is activated for approx. 90 seconds.

    Once the seat belt has been fastened, the seat-belt warning lamp goes out. The audible seat-belt warning is deactivated.

    If the seat belt has not  been fastened by the end of the acoustic seat-belt warning, the seat-belt warning lamp will stay on.

  • Passenger side:

    After approximately 15 seconds, the seat-belt warning lamp will light up and an audible seat-belt warning will be issued for approx. 90 seconds.

    Once the seat belt has been fastened, the seat-belt warning lamp goes out. The audible seat-belt warning is deactivated.

    If the seat belt has not  been fastened by the end of the acoustic seat-belt warning, the seat-belt warning lamp and the acoustic seat-belt warning are deactivated.