Passive Safety Systems in a Car — Guide To Automotive Terms

Even the safest drivers can encounter unexpected situations on the road. Cars are engineered with a multitude of safety features to protect occupants in the event of a collision. These passive safety systems don’t prevent accidents but rather come into play after a crash has occurred to minimise injuries. 

From the familiar seatbelt to the innovative pop-up bonnet, let’s explore the various components that make up a car’s passive safety arsenal and understand how they work together to keep you safe on the journey.

Before we delve into the world of passive safety systems in a car, let us look at some of the highlights of safety systems.

These systems are designed to minimize injuries to occupants in the event of a crash. They come into play after a collision has occurred and cannot prevent the accident itself. 

These systems are designed to help drivers avoid accidents altogether. They use a variety of sensors and technologies to monitor the driving environment and warn drivers of potential hazards or even take corrective actions.

Now that we have an understanding of when passive safety in cars is effective, let us look at various systems that help occupants after a crash.

Seatbelts are the cornerstone of passive safety. They restrain occupants during a crash, preventing them from being ejected from the vehicle. The most common type is the 3-point belt, which distributes crash forces across the chest, hips, and shoulders. 

Airbags are like lightning-fast inflatable cushions strategically positioned within the car’s interior. Upon impact, sensors trigger their deployment at an incredible speed (up to 320km/h!). 

Airbags create a protective barrier between occupants and the vehicle’s hard surfaces, mitigating potential injuries to the head, torso, knees, and even the sides of the body depending on the airbag type.

This is the most common type, where a single propellant rapidly inflates the airbag upon sensor detection of a crash.

A more sophisticated system that uses two stages of propellant deployment. The first stage provides initial inflation, while the second stage tailors the inflation pressure based on the severity of the crash for potentially gentler occupant cushioning.

These sensors detect the force of a collision and trigger airbag deployment.

This system incorporates occupancy sensors that can detect the presence and weight of a passenger in a seat. This allows the airbag system to adjust deployment parameters or even deactivate airbags in unoccupied seats or even for child safety seats.

SRS stands for Supplemental Restraint System. It’s a broader term encompassing all the airbag systems within a car. So, all the airbags you encounter (front, side, knee, curtain, etc.) are technically part of the SRS Airbag system.

Crumple zones are designed to crumple and absorb the force of a collision in a controlled manner. These engineered sections are typically located at the front and rear of the car. By deforming upon impact, crumple zones significantly reduce the energy transferred to the passenger compartment, keeping occupants safe.

Head restraints integrated into the back of seats, aim to minimize the risk of whiplash by providing support for the head and neck, preventing them from hyperextending. Some head restraints are adjustable to ensure proper positioning for optimal protection.

The passenger compartment is a high-strength steel structure designed to form a protective cage around occupants in a crash. This cage resists deformation, safeguarding the integrity of the survival space within the vehicle.

Car windows are made from laminated glass, a type of safety glass that holds together upon impact. This prevents dangerous shards from scattering and causing injuries.

Strategic padding is placed on the dashboard, steering wheel, and other interior components to absorb impact and reduce potential injuries during a collision.

These systems automatically lock the car doors upon reaching a certain speed, preventing occupants from being ejected in a crash. Additionally, they may unlock automatically upon airbag deployment to facilitate emergency egress.

The steering column is designed to collapse upon impact, absorbing energy and preventing serious chest injuries to the driver.

A collision can damage fuel lines, creating a fire risk.  A fuel shut-off switch automatically cuts off the fuel supply in the event of an impact, minimizing the chance of a post-crash fire.

In a pedestrian collision, a pop-up bonnet raises slightly upon impact, creating more space between the engine and the hood. This extra space helps absorb impact and potentially reduces injuries to the pedestrian.

A reinforced roof prevents the car from caving in and crushing occupants during a rollover accident.

Rearview mirrors provide drivers with a clear view behind the vehicle, allowing them to change lanes and manoeuvre safely. Rearview mirrors, made from shatter-resistant glass to minimize the risk of injury from broken fragments, offer drivers a clear view of the vehicle.

We have covered the important terminology involved in a car’s passive safety systems. Read other automotive term guides here. If you are new to the automotive terminologies guide, we recommend giving the beginner’s guide a read.

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