How your car works - Airbags & Impact Structures

Probably the most important safety devices since the seatbelt
The Airbag has been introduced into cars in the UK over the last 10 years or so. The Airbag's main function is to reduce injuries caused as a result of your head or body hitting the steering wheel or dashboard during an accident. The introduction of Airbags has not been without problems. In America during the 1970s, Airbags were used but they were unreliable. For example, they could deploy by just going over a large hole or bump in the road, with unpredictable and dramatic results. It wasn't until the mid 1990s that they once more made their appearance in production cars because by then they had been made totally reliable.

Today the device is considered to be one of the most important safety devices since the seatbelt was first introduced in the 1960s.

The technology has been further developed to include many different Airbag deployment systems that are even safer for the occupants. There are many other "Supplemental Restraint Systems" (SRS) found in modern cars and they include such items as Seatbelt Pretensioners, Side Impact Airbags inside the rear door pillars and even Airbags in the doors themselves, to name but a few.

But how does it all work?
Well, basically it is all done with controlled explosives!

When a vehicle has an accident over a certain speed (e.g. 20mph) a sensor will trigger the Airbags and other safety systems within a split second.

Research by the motor manufacturers over the years has enabled them to reduce further the deployment time, allowing improved protection and less danger of serious injury.

Remember that babies and all frail and weak persons must not be positioned in front of or near an Airbag. In some cases your can switch the passenger Airbag or system off. Consult your car's handbook or your Unipart Car Care Centre.

The typical standard Airbag is housed in the centre of the steering wheel along with the inflator. To inflate the Airbag, there is an igniter that activates some compressed gas capsules and these fill the bag with an inert gas when an impact above a certain force is sensed. The whole inflation process occurs within a split second and the bag is completely deployed in less than a second, enough time to restrain the occupant.

The Airbag will not activate without the system being given the go-ahead by the on-board sensors. They have to sense vehicle speed (generally over 5 mph), deceleration of the vehicle and any impact to the front, rear or sides of the car body for the system to become active. When this information is received by the Airbag Control Unit it is processed and an instruction is sent to the Airbag for it to deploy.

Where are the Airbags?
The Airbags are situated in the steering wheel centre, in the dashboard on the passenger side and in the side of the seats, depending on the make and model of car.

If the Airbag were to deploy it would have to be replaced by trained technicians who would have the special knowledge and equipment to safely install a new one. Your local garage will be able to carry out this work. For safety reasons, any work on the Airbag or SRS systems must not be carried out by anyone unfamiliar with the correct repair procedures. It is very dangerous to attempt to remove them yourself.

Impact Structures
Another new safety development in cars is the introduction of Impact Structures in to the main structure of the vehicle. This technology was introduced to contain the damage within the 'crumple zones' of the car and reduce injury to the occupants inside.

But what is a crumple zone? It is the area outside of the passenger compartment, e.g. the front or rear bodywork and even the doors. The danger is that in an accident the impact will force the metalwork into the passenger area. With improved crumple zones the energy is absorbed by the controlled deforming of the metal of the bodywork and so the occupants will be less exposed to the effects of the impact. Today, enormous attention is paid to safety and motor manufacturers are constantly improving their designs to incorporate better and safer crumple zones.

A lot of cars now also have side impact bars to lessen the amount of bodywork distortion inside the passenger and driver area. This technology has indeed proven to decrease the amount of injuries in the event of an accident.

The principle behind impact structures is that the energy created during an accident is intentionally directed to the floor, bulkhead, sills, roof, bonnet; areas where these structures absorb the energy and reduce damage and intrusion to the passenger compartment. With these structures you are more likely to walk away from an accident. Your car however may be badly damaged and usually this involves a great deal of expense to put right. After all, these days even after a light shunt it can cost a fortune. Remember the days of big metal bumpers. Well that was okay in the good old days but cars were progressively getting heavier and less economical. So these were progressively ditched in favour of crumple zones, making our cars a lot safer in the process.

Caring for your car's safety systems

• Do not allow untrained personnel to carry out repairs to any part of the SRS systems. There is the chance of personal injury and also for the system to not function correctly when it is needed.
• After an accident, even if the Airbag doesn't deploy, take the car immediately to your nearest garage for diagnosis and possible replacement of the Airbag and Controller. If this is not done then the chances are that the Airbag may not work if needed in the event of another accident.
• If the SRS fault warning lamp illuminates on the instrument panel take your car in for the fault to be diagnosed as soon as possible.