For some time, airbag applications have broadened beyond frontal airbags to curtain, knee, foot, seatbelt and pedestrian bags. While most cars today contain an average of seven airbags, some believe that as many as 23 airbags could be needed to protect occupants from every conceivable injury. Matthew Beecham reports on the evolution of the airbag.
An emergency drill onboard AIDAsol cruise ship in 2019. Image: MikhailBerkut / Shutterstock.com
The idea for the airbag was attributed, amongst others, to the hobby inventor, Walter Linderer. In the 1950s, he had designed what he described as an “inflatable container in a folded state, which automatically inflates in the event of danger”. Daimler picked up the idea and, in December 1980, launched a limited number of S-Class Saloons with a passive safety restraint system consisting of an airbag and seatbelt tensioner. The combination was offered as an optional extra.
As airbag components became increasingly smaller, it was possible to squeeze airbags into other parts of the carbin, apart from in the steering wheel or glove box. This offered an ideal opportunity for developers since although the first airbags could minimise the impact of a head-on collision, there were many other potential accident scenarios.
In 1995, the side airbag was launched in the Mercedes E-Class, a window airbag was added in 1998 with a head/thoraxsidebag to follow in 2001, a knee airbag in 2009 and thorax/pelvis sidebag, the cushion bag and the very compact inflatable belt airbag in 2013. The latest generation Mercedes S-Class incorporates rear airbags that protect passengers in frontal crashes.
While it’s a fallacy to believe we can escape injury following a serious car crash, passive safety devices to protect all parts of the body have come a long way sincethe original idea for airbags was commercialised. Although safety systems have almost reached saturation point regarding the number of airbags dotted around a car, electronics enabling them to become smarter.
New car assessment programmes, such as EuroNCAP have also contributed towards raising consumer awareness of passive safety technologies. More than 78,000 lives have been saved since Euro NCAP’s crash safety tests were launched in 1997.In turn, their heightened awareness has led safety campaigners to put further pressure on legislators to raise standards.
Although the airbag is a mature product, manufacturers continue to innovate and find new applications. For instance, Toyoda Gosei has developed a steering wheel airbag with a new structure offering greater occupant protection. Launched on the Honda Civic in North America last June, the airbag uses an innovative doughnut-shaped structure to cradle and hold the driver’s head to reduce rotation in the event of a collision.
In pushing back the technical boundaries, the Honda Jazz is the first of the brand’s models in Europe, and the first model in its class to market, to feature front-centre airbag technology as standard. The new front centre airbag is fitted within the back of the driver’s seat and expands into the space between driver and passenger. This airbag, one of 10 in the latest Jazz avoids direct contact and reduces driver-passenger impact in the event of a side-on collision. To ensure the airbag is accurately placed to deliver maximum protection during deployment, the airbag uses three attachment tethers which guide the airbag around the driver in a curve. To realise this new feature, the engineering team developed the airbag unit to fit within the upper bolster of the newly designed driver’s seat.
Veoneer,emotion3D and AVL are partnering to develop a personalised and situation-aware restraint control technology system. Veoneer says current passive safety systems, such as airbags follow a ‘few-sizes-fit-all’ development approach and thus perform best for a small number of specified body physiques; the most common one is the average male: 175 cm and 78 kg. This is suboptimal for everybody who deviates from these averages; children, elderly people and some women. A study conducted by the University of Virginia found seatbelt-wearing female occupants are 73% more likely to suffer from serious injuries than seatbelt-wearing males. As long as passive safety systems cannot distinguish between the occupant’s characteristics, it is impossible to achieve optimal protection for everybody. During the next 24 months, the project partners will develop a restraint control system able to personalise the actions of passive safety systems in event of a crash. Using a 3D sensor for understanding the vehicle interior, the system will consider a range of relevant, personal and situational factors such as body physique, position and pose, weight and gender.
As the number of e-scooters grows across cities so does the need to provide safety systems for those using them. Last year, Autoliv completed the first crash test with a concept airbag for e-scooters. Initial results indicate the e-scooter airbag reduces injuries to a rider's head and chest.
Passive safety systems for AVs
Looking further ahead, passive safety systems for autonomous vehicles (AVs) are under development. While SAE Level 4 and 5 AVs bring many opportunities to suppliers and OEMs in terms of being able to rethink the vehicle cabin, there are also many additional hurdles to overcome. For example, many of today's well-understood safety parameters are formulated with the knowledge that the drivers and passengers will be forward-facing with three-point safety belts and other occupant restraint systems designed to these boundaries. Rearranging the vehicle cabin, at L4 autonomy and beyond, with a multitude of different seating arrangements introduces far more complexity to passive safety in the cabin and could mean that many of the OEMs' and suppliers' visions for future vehicle interiors are never fully realised.
Following the debut of Amazon-owned startupZoox's fully autonomous vehicle, ZF announced last December that it would provide occupant safety systems and chassis modules for the new robo-taxi. The products supplied include airbags mounted on the roof and in the seats. The challenge, ZF said, was the "campfire seating position" which means that two passengers will be forward-looking and two passengers facing the rear. Usual occupant safety systems are optimised for forward-looking occupants so the safety concept for this robo-taxi has been specifically developed for these new seating positions.
Vehicles that operate autonomously and/or in defined environments may not require the same levels of crash protection. This, in turn, implies different designs and materials choices that have implications for vehicle lightweighting. For instance, safety standards may be relaxed, allowing for a steel framework to be replaced by lighter plastics. In addition, changes in design could include a lower emphasis on visibility outside the car, and a greater emphasis on communication and entertainment in the vehicle.
Further out, plastic content in light vehicles could again start to rise due toseveral factors such as electric vehicle penetration and whether there's significant AV take-up, i.e. if you don't crash then you don't need all those crumple zones.
What does the future hold?
Occupant restraint systems are thankfully no longer the preserve of the luxury car segment.Whatever the future might hold, it is clear that driver and passenger experience is changing, with advanced passive safety technologies giving us all a greater degree of comfort with each new car model.
Airbag in the steering wheel: The airbag supplements the seat belt by cushioning the occupant’s head and upper body in the event of a head-on impact to help prevent serious injury. Photo from 2005. Credit: Daimler