When you think about safety in cars, seat belts are likely the first feature that comes to mind. However, over the past few decades, another vital safety device has become standard in most vehicles: airbags. More specifically, these are known as Supplementary Restraint Systems (SRS) airbags. The term "supplementary" means that airbags are not meant to be a replacement for seat belts; they are crafted to work together with seat belts to enhance passenger safety.
SRS airbags reduce the risk of serious injury during an accident by cushioning the impact on passengers' heads, chests, and other parts of the body. Read on to explore the different types of SRS airbags and why they are essential to car safety.
Different Types of SRS Airbags
SRS airbags come in many forms, and each type is designed to offer protection for specific body parts or during certain types of collisions. Here are the most common types:
- Driver Airbags: These airbags are located within the steering wheel and are crafted to protect the driver in a frontal collision. They lessen the possibility of a head or chest collision with the steering wheel.
- Passenger Airbags: Passenger airbags are installed in the dashboard on the front passenger side. They protect the passenger’s head and chest during a frontal impact.
- Side Airbags: Side airbags are positioned inside the sides of the car seats or door panels. Their primary role is to protect the chest, abdomen, and pelvis of the driver or passengers during side-impact collisions.
- Curtain Airbags: Curtain airbags are installed along the roof edges inside the car. They deploy downwards like a curtain to shield the heads of passengers from side windows and prevent head injuries during side impacts or rollover accidents.
- Knee Airbags: Knee airbags are found beneath the dashboard or steering wheel. They prevent injuries to the knees and legs by cushioning them during a crash.
- Rear Seat Airbags: These airbags are becoming more common in newer vehicles. They protect passengers sitting in the back seats, especially in frontal collisions.
How Does the SRS System Work?
The SRS system is a highly advanced safety mechanism that operates within milliseconds. Here’s a step-by-step explanation of how SRS in airbags works:
1. Crash Detection:
Sensors are usually placed around the vehicle, including the front, sides, and rear. These sensors are designed to measure the force, speed, and direction of a collision. For example, during a crash, accelerometers detect rapid deceleration while pressure sensors monitor changes in the car's structural pressure. These sensors immediately transmit data to the Airbag Control Unit (ACU) during a collision. This step is critical because it determines whether the impact is significant enough to deploy the airbags. For instance, minor bumps or slow-speed collisions usually don’t trigger airbag deployment to avoid unnecessary activation.
2. Data Processing:
Once the sensors relay information, the ACU acts as the system's brain, analysing the data in real time. The ACU evaluates factors such as the crash’s intensity, angle of impact, and which part of the vehicle is involved. If the data indicates a severe crash—typically one that would risk serious injury to occupants—the ACU activates the airbag system. This process happens in milliseconds, ensuring a rapid response during emergencies. The ACU is also programmed to prevent deployment in non-critical situations, such as when seat belts alone provide sufficient protection.
3. Inflation Process:
After the ACU decides to deploy the airbags, it sends an electric indicator to the inflator units inside the airbag modules. The inflator contains chemicals such as sodium azide or a similar propellant, which rapidly reacts to produce gas—commonly nitrogen or argon. This gas fills the airbag almost instantly, creating a cushioning barrier between the occupant and the car’s interior surfaces, such as the steering wheel, dashboard, or windows. This reaction is controlled to ensure the airbag inflates at just the right speed to maximise protection without causing injury.
4. Deployment:
As the airbag inflates, it bursts out of its storage compartment with great force. For front airbags, this compartment is typically the driver’s steering wheel and the passenger’s dashboard. Side airbags deploy from the side of seats or door panels, while curtain airbags emerge from the roof lining. The speed of deployment ensures that the airbags are fully inflated by the time the occupant begins moving forward due to the collision. This cushioning effect absorbs much of the impact's energy, significantly reducing the risk of serious injury to the head, chest, and other vital areas.
5. Deflation:
After providing protection during the crash, the airbag deflates almost as quickly as it inflates. Small vent holes are built into the fabric of the airbag to allow the gas to escape safely. This deflation process ensures that the airbag doesn’t obstruct the driver’s visibility or trap occupants, which is especially important if they need to exit the vehicle quickly. Additionally, deflation minimises the risk of secondary injuries caused by prolonged pressure from the inflated airbag.