The science and logic of why, where and how airbags deploy in a car

Mahindra is facing flak over the accident involving a Scorpio, in which the SUV's airbags did not deploy. This has resulted in the affected family filing a lawsuit against Mahindra Group's chairman Anand Mahindra and 12 others. In response, Mahindra has issued a statement clarifying why the airbags onboard the SUV were not deployed.

This issue has again fuelled the discussion around car safety and the active and passive safety technologies - and features - used in modern cars. An airbag is a major passive safety device that is deployed during major collisions and prevents the occupants from hitting hard surfaces inside the vehicle such as the dashboard, windshield, steering wheel etc. This eventually comes as a device to mitigate the physical damage an occupant may face during an accident.

Airbags have been use in the cars for decades. In 1973, Oldsmobile Toronado was the first car ever in which passenger airbags were installed. With this, General Motors (GM) became one of the first car manufacturers to offer airbags in its cars. Since then, airbag technology has evolved significantly becoming more efficient, reliable and safer. In many car crashes around the world, this technology has saved the lives of many people.

The National Highway Traffic Safety Administration (NHTSA) estimates that frontal airbags have saved more than 50,000 lives since 1987 in the US. In 2016 alone, the road safety agency estimated that airbags saved 2,756 lives. It further claimed that airbags and seat belts combined, reduce the risk of death in frontal crashes by 61 per cent. In frontal crashes, front airbags reduce driver fatalities by 29 per cent and fatalities of front-seat passengers by 32 per cent. However, there have been downsides to airbag technology as well, as the malfunctioning system has also killed people. NHTSA has reported that between 1996 and 2000, airbags killed 116 children and 75 adults in the US.

Here is a comprehensive explainer shedding light on how an airbag works, what are the triggering factors for airbag deployment and the impact of it.

Types of airbags

In modern cars, there are three different types of airbags. While the most common types of airbags used in cars are the frontal ones, protecting the driver and the front passenger, there are side airbags to mitigate side impact injuries and side curtain airbags that protect the occupants in case of rollover crashes.

Where are airbags placed in a car?

Airbags are strategically positioned in a range of locations inside a car's cabin. The most common airbags, which are the frontal airbags are positioned within the steering wheel of the vehicle and for the front passenger, it is located inside the dashboard. The side airbags and side curtain airbags are contained in the side cage of the vehicle, above or around the windows.

How does an airbag work?

Airbags are made of very lightweight material and act like a gas-filled balloon when they are deployed. The technology comprises sensors that sense the impact in case of a crash and send a signal to the ignition relay within the airbag system. This results in the airbag quickly filling with gas and deploying after breaking the upper concealing cover.

This whole process takes just a fraction of a second to initiate and complete. The airbags act as a cushion for the occupants, preventing them from hitting hard surfaces, which helps in mitigating head injuries, lacerations, spinal cord injuries etc.

Do airbags truly save lives?

While airbags have been designed to protect vehicle occupants from critical injuries, which could be life-threatening, the airbag deployment technology is far from perfect. The airbag sensors trigger activation of the system, but they can malfunction, resulting in the airbags inflating at the wrong moments. Also, malfunction in the sensors can also cause failure to inflate the airbag.

Besides that, the airbags deploy at an insanely high speed, measuring at about 25 kmph, which can impact the occupant negatively and injure him or her if other factors are at play like the seatbelt is not fastened or the proper gap between the steering wheel or dashboard and the front seats are not maintained.

Also, the airbags do not inflate using the normal air or oxygen. Instead, they rely on gases that can cause respiratory issues. In case of a malfunctioning airbag deployment system, an eye injury is highly possible. On the other side, a malfunctioning of the system can spray shrapnel through the cabin injuring the occupants instead of saving them.

However, in most cases, the airbags act as passive safety devices for the occupants and are considered one of the major safety features in modern vehicles.