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Since the airbag was developed and later mandated, safety engineers have been working on the problem of preventing injury from the bag itself.

The deployment of an airbag is a violent event. The bag has to reach full volume in the tenth of a second after a crash, before the occupant it is designed to protect is thrown forward into it by the force of the crash.

Several developments have taken place to mitigate injury from being struck by the bag, mostly related to the size and location of the occupant in the front passenger seat.

Among the first concerns and problems were related to children in child seats. This led to the ability to switch off the bag in vehicles with no rear seat in which to put the child carrier.

Subsequent developments have led to the development of dual and multistage deployment. In these systems, sensors allow the bag to deploy more slowly -- or with less force -- if the occupant is seated far from the instrument panel or is of a diminutive stature. The bag can still provide maximum protection because the occupant is lighter and requires less bag volume, or will take longer to be propelled into the bag from a position further from it.

Peripheral developments have included seatbelt pretensioners to tug the belt snug, holding the occupant in place for maximum protection, and force limiters which allow the belts to be played out slightly in a crash at the moment of maximum load to reduce pressure on the chest.

All of these efforts have been based on the size or weight of the occupant.

But scientists in Europe are now studying a system that takes into account the condition of the occupant, centred around the fact that as we age, our bones become weaker and more easily broken. In other words, tolerance to the extreme loads placed on our bone structure by belts and bags in a crash diminishes with age. Current sensor systems that deploy according to weight and location do not take into account bone strength -- they treat a 100-kilogram 75-year-old the same as a 20-year-old.

Research shows that older drivers and people with weak bones or medical conditions such as osteoporosis often suffer fractured ribs and sternums as the result of the deployment of airbags and the high forces applied by belts.

Research also shows that, while these injuries can be serious, they are clearly preferable to the damage that would occur with no protection. The idea is to use new technology to enhance the advantages of belts and bags to this segment of the population.

A consortium of universities, instrument and electronic component manufacturers and auto makers (Jaguar and Nissan) are involved in a three-year project funded by the U.K. Department for Transport. The study is called Bone Scanning for Occupant Safety (Boscos).

The objective of Boscos is to initiate development of a system that can make an assessment of the bone characteristics of each occupant in a vehicle in order to estimate their skeletal strengths.

"The seatbelt and airbag characteristics can therefore be adjusted to deliver optimum levels of protection specifically for each occupant," the consortium says.

The project is working on a bone-scanning system that uses ultrasound technology to detect bone strength and set bag and belt deployments accordingly.

The current system relies on the occupants inserting a finger into a reader that detects bone density and occupant position -- allowing the various related sensors to determine the most effective protection. There are no plans or timelines at this time for the deployment of such systems.

globeauto@globeandmail.ca