Tests break down the barriers to safety

MOTOR cars incorporating structural safety as an important design criteria are a relatively new phenomenon in the motoring industry.

It is not that long ago that "passive" safety, or what a vehicle can do to protect its occupants during a crash, became a big issue.

In the 1970s and 1980s, there was a large credibility gap between those who treated passive safety as important, and those who thought little about it other than paying lip service to legislated requirements.

Today the issue has heated up and car safety is being publicized, commercially exploited and politicized to an astounding degree.

At the center of all the commotion is the issue of what truly makes a car safe.

For decades now, many carmakers have operated safety laboratories that allow some degree of assessment of safety standards -- and one of the common yardsticks is the barrier test.

The barrier test was originally conceived to determine how a car's structure behaved in a significant front-end crash.

Test "mules" were sent head-first into massive concrete barriers at specific velocities, photographed by a battery of high-speed cameras and measured and analyzed by engineers afterward.

On board were specially designed "dummies" that more or less replicated what would have happened to a human being inside the vehicle.

The tests, by today's standards and with today's ever- increasing knowledge of the things that contribute to car safety, were essentially primitive, but they did allow safety engineers to develop a number of significant design principles that are still accepted as basically sound in terms of providing a secure, safe "cocoon" to protect passengers.

The principle is this: the front and rear ends of the vehicle are designed so they are relatively "soft" and capable of absorbing much of the collision force, while maintaining a basically rigid, strong "cage" surrounding the occupants.

This principle, which first came to light in Mercedes-Benz vehicles from the early 1960s, still applies today, but has been refined to almost amazing degrees as carmakers collect data both from laboratory tests and "real-life" accident situations out on the road.

Computer simulation during the design phase has also provided carmakers with an extra tool that enables crashworthy structures to be developed even before prototypes are built.

The barrier test itself, has become increasingly more complicated as it attempts to deal with the almost infinite variables that can occur in real accident situations.

Today carmakers use "offset" tests with varying degrees of overlap in addition to full-frontal tests because offset collisions, in which only part of the front of the car is involved in the impact, are more common than direct head-on collisions.

As safety science has progressed, so the barriers themselves have changed: offset impact tests are now conducted against a "crushable" barrier that actually absorbs some of the forces itself, in the same manner as another vehicle involved in the collision.

How a vehicle behaves in a collision, and the effect it has on the other vehicle with which it has impacted, is the subject of involved study by safety engineers.

In recent years it has been generally agreed that some cars that comfortably survive a direct head-on impact may not do so well in an offset crash - and vice versa.

The challenge is to construct a car that behaves in the most protective way possible in all types of impacts.

Measuring the effectiveness of the design is the anthropomorphic crash dummy seated in the test vehicle.

These are able to demonstrate, with astonishing degrees of accuracy, the injuries that would have been inflicted on a human passenger and are now used as the criteria against which a car's safety standards are judged.

Legislated safety standards governing the introduction of new cars in many countries now stipulate the levels of protection, measured by dummy injury readings in areas such as the head ("HIC" or Head Injury Criteria value), chest and leg areas, that must be achieved.

Future standards will involve side and rear-impact, rollovers and other tests, but debate is already flaring on the relevancy of laboratory tests compared to the "real-world" studies conducted during safety research by a number of European carmakers.

These manufacturers say a vehicle designed to perform well in a basic barrier test may not be so safe on the road where crashes are not so simple and straightforward.

As a senior safety engineer from one European car company recently said "I don't see many crash barriers out there on the highway."

Barrier tests remain vital to the development of safe car structures but it is becoming clear that while they do provide important information, they are not able to give the full safety picture.