Knee airbags
SécuritéAverage price
300€ - 1000€
The knee airbag is a passive safety device designed to protect the lower limbs of the driver and, in some cases, the front passenger during a frontal collision. Integrated into the lower part of the dashboard—beneath the steering column for the driver and near the glove compartment for the passenger—it deploys in milliseconds in the event of an impact. Its primary role is to limit violent contact between the knees and shins and the rigid structures of the cabin. By acting as a cushion, it absorbs part of the impact energy and distributes forces over a larger surface area, thereby significantly reducing the risk of femur, tibia, or kneecap fractures. Additionally, the knee airbag helps keep the occupant's body in an optimal position in the seat, preventing 'submarining' (sliding under the seatbelt). This allows other restraint systems, such as the pretensioner seatbelt and the front airbag, to function with maximum efficiency. Initially reserved for high-end vehicles, this equipment is now increasingly common across all segments of the automotive market, reflecting its importance in improving overall occupant safety.
Benefits
- ✓Significantly reduces the risk of serious leg and knee injuries.
- ✓Improves the efficiency of front airbags and seatbelts.
- ✓Prevents the 'submarining' phenomenon during a frontal collision.
- ✓Helps achieve better safety test ratings (Euro NCAP).
Learn more
What is a knee airbag?
The knee airbag is a crucial component of a modern vehicle's Supplemental Restraint System (SRS). As the name suggests, it is specifically designed to protect the lower limbs—particularly the knees, shins, and femurs—of the driver and sometimes the front passenger. In the event of a frontal collision, it deploys from the lower part of the dashboard: beneath the steering column for the driver and above the floorboard, below the glove compartment, for the passenger. Its near-instantaneous deployment creates a cushioning barrier between the occupants' legs and the rigid components of the dashboard, thereby preventing often severe and disabling injuries.
How do knee airbags work?
The operation of knee airbags is synchronized with the vehicle's overall safety system. Acceleration sensors, positioned at strategic points around the car, detect the sudden deceleration characteristic of a frontal impact. If the force of the crash exceeds a predefined threshold, the central control unit sends an electrical signal to the knee airbag inflator. A chemical reaction then produces a large volume of gas (typically nitrogen) that fills the cushion in less than 40 milliseconds. The airbag deploys to cushion the impact of the knees, then rapidly deflates so as not to hinder the occupant's movements after the collision. It works in perfect coordination with front airbags and pretensioner seatbelts to provide comprehensive protection.
Key benefits of the knee airbag
An increasingly standardized safety technology
While knee airbags were once the exclusive domain of luxury sedans, their proven effectiveness has led to their democratization. They are now standard equipment on many models in the intermediate and compact segments. They are part of a holistic passive safety approach aimed at protecting occupants from all angles, complementing side airbags and curtain airbags. By acting as the primary point of contact for the lower body, they play a fundamental role in the protection chain orchestrated by the vehicle during an accident.
Associated equipment
Curtain airbags
Curtain airbags, also known as 'curtain airbags' or Inflatable Tubular Structure (ITS), are essential passive safety devices in modern vehicles. Integrated into the headliner (roof lining) above the side windows, they deploy vertically downwards, like a curtain, in the event of a severe side impact or rollover. Their primary objective is to protect the heads of occupants, whether seated in the front or the rear, by creating a protective cushion between their heads and hard interior surfaces, such as windows, door pillars (B-pillar, C-pillar), or external objects. Unlike front or side airbags (which protect the thorax), curtain airbags remain inflated longer (several seconds) to provide continuous protection during multiple impacts or rollovers, and to prevent passenger ejection. Triggered by lateral acceleration sensors and gyroscopes, they are an integral part of the Supplemental Restraint System (SRS) and are a major criterion in safety assessments such as Euro NCAP. Today, they are virtually standard on new cars sold on the French market.
ESP
ESP, or Electronic Stability Program, is an essential active safety system in modern vehicles, also known as Electronic Stability Control. Its primary role is to keep the vehicle on the trajectory intended by the driver, by preventing loss of grip and skidding. To do this, the ESP uses a series of sensors (wheel speed, steering wheel angle, lateral acceleration, yaw) that continuously analyze the consistency between the direction desired by the driver and the actual behavior of the car. If a discrepancy is detected, signaling the onset of understeer (the front wheels skid) or oversteer (the rear wheels skid), the system intervenes in a fraction of a second. It independently brakes one or more wheels and can also reduce engine power to bring the vehicle back onto the correct trajectory. Mandatory on all new vehicles sold in Europe since 2014, ESP is an electronic guardian angel that significantly increases safety during emergency avoidance maneuvers, in tight corners, or on slippery surfaces (rain, snow, ice). It works in synergy with other aids such as ABS and ASR (traction control).
Frontal airbags
Frontal airbags are a fundamental passive safety feature in modern vehicles. Designed to protect the driver and front passenger in the event of a frontal or near-frontal collision, they are an integral part of the Supplemental Restraint System (SRS). Their function is to deploy in a fraction of a second to create a cushioning pad between the occupant and the rigid parts of the cabin, such as the steering wheel or dashboard. The system is activated by sensors (accelerometers) that detect sudden and sharp deceleration, which is characteristic of an impact. An electronic control unit analyzes these signals and, if the crash is deemed sufficiently severe, triggers a pyrotechnic gas generator. This produces a large amount of gas (primarily harmless nitrogen) that inflates the nylon bag in less than 50 milliseconds. Modern frontal airbags are often adaptive (dual-stage or multi-stage), adjusting their deployment force based on the severity of the crash, seat position, or even the occupant's weight. They are designed to work in synergy with the seatbelt, which remains the primary restraint device.
Seatbelts with pretensioners
Seatbelts with pretensioners are a pillar of modern passive safety, acting as the first link in the protection chain in the event of a collision. This intelligent device does not simply restrain the occupant; it positions them optimally even before the peak of the impact. As soon as sudden deceleration is detected by the vehicle's sensors, the electronic control unit (ECU) sends a signal that triggers, within milliseconds, a pyrotechnic or mechanical mechanism. The latter powerfully retracts the seatbelt webbing, eliminating all slack and firmly pressing the occupant against the seat backrest. This preventive action is crucial: it ensures that the body is in the ideal position to benefit from the maximum effectiveness of the airbag, which deploys immediately afterwards. The pretensioner works in perfect synergy with the load limiter, which then slightly releases the tension to cushion the pressure on the chest and prevent injuries. Integrated into the retractor or the buckle, this system is now an essential standard equipment on all new vehicles, playing a decisive role in reducing the severity of injuries.
Side airbags
Side airbags are an essential passive safety feature in modern automobiles, belonging to the Supplemental Restraint System (SRS). Their mission is to protect occupants in the event of a side collision, one of the most dangerous situations. There are two main types: the thorax airbag, generally integrated into the side of the seat backrest, and the curtain airbag, housed in the vehicle's headliner above the windows. During a side impact, pressure sensors and accelerometers send information to the Electronic Control Unit (ECU). Within milliseconds, if the impact is deemed severe, the ECU triggers deployment. The thorax airbag forms a protective barrier for the torso, abdomen, and pelvis. Simultaneously or independently, the curtain airbag deploys like a curtain along the windows, protecting the heads of front and rear passengers against impact with the glass, door pillar, or external objects. This technology has drastically reduced the severity of head and chest injuries, contributing significantly to achieving high crash-test ratings, notably those of Euro NCAP.