The knee airbag on the driver's side is located in the dash panel underneath the steering wheel Fig. 1.

The knee airbag provides extra protection for the driver's knees and thighs in addition to the protection already given by the seat belt.

In addition to its normal function of restraining an occupant, the seat belt also holds the driver in a position where the airbag can provide extra protection in a frontal collision.

The airbag system is just one component of the Audi A3's restraint system and cannot replace the function of the seat belts. Please always remember that the airbags can only protect you if you are wearing your seat belt properly. That is why it is so important to wear your seat belt at all times (not just because it's the law) ►Link.

Please also bear in mind that the airbags are only inflated in certain types of accident and that they can only be triggered once. The seat belts are also intended to protect you in situations where the airbags are not triggered or have already been triggered (e.g. if your Audi A3 collides with a second Audi A3 following an initial impact).

That is just one reason why an airbag cannot replace a seat belt. The airbag system is most effective when used in conjunction with the seat belts. Always fasten your seat belt properly for this reason.

Please note that, although the knee airbag system is designed to reduce the risk of serious injury, the airbags can cause other injuries when inflated (such as inflammation, bruising, abrasion and friction burns).