Belt up snuggly in your car to survive unwanted crashes

By Barry Lake

WATCH motor racing on television and you see drivers survive some horrendous crashes. How do they do it? Well, there are a number of factors but, among them, is the fact that they are strapped securely in their driving seats.

They do this by wearing a snug-fitting six-point harness that includes lap belts, two shoulder harnesses, and two crutch straps which feed under and around the legs and up to the central quick- release buckle mounted above the pelvic area of the driver's body.

Most everyday, motorists would find such a belt claustrophobic, to say the least, not to mention inconvenient. Unlike race drivers, we don't always have someone on hand to Bassist us to "belt up".

For road use, the now ubiquitous retractable lap-sash belt is far more convenient.

Road fatalities and serious injuries in Australia fell dramatically, virtually overnight, when seat belt legislation was introduced back in the late 1960s.

Unfortunately, many drivers and passengers wore those original belts far too loosely to be of full benefit to them.

The introduction of automatically retracting belts was a big step forward in that those careless people now had a belt that fitted their bodies much more closely than ever before.

It wasn't quite so good for those who were thoughtful enough to adjust the older-style belts so they fitted very snugly.

Inevitably, a retractable belt had to "give" a little before it locked up, so it wasn't quite as tight, nor as effective, as a well-fitted belt.

So the next step was to provide what are termed "seat belt pretensioners". This is a triggering device attached to a mechanism that pulls the seat belt snugly against the occupant in the event of a crash or collision.

The sensor which triggers the air bag in the event of an impact above a certain force, sends a signal to the seat belt pretensioners to tell them to pull the belts tight.

Seat belt tensioning occurs at lower speeds than air bag deployment because air bags are required only for higher impact collisions. Belts need to be tensioned at much lower speeds.

It is the belts that do all the work in minor crashes, and a large part of the job in major collisions. The air bag is an additional device which prevents the driver's head and chest from hitting the steering wheel, and the front seat passenger's head and chest from impact with the dashboard.

Tightening the belts before the occupant is flung against them does two things: it minimizes the possibility of the wearer sliding out from behind the sash belt, or from "submarining" down under the lap belt; and it ensures they gain the full benefit of the planned stretch of the belts to absorb much of the force of the crash.

When the sensor detects a collision, it sends a signal to the pretensioner which, depending on its type, either fires a pyrotechnic (explosive) device, or releases a highly tensioned spring. Either way, the belt is pulled tight -- but not excessively so -- against the wearer.

These devices are most commonly attached to the buckle end of the belt system and pull the buckle extremely rapidly a predetermined distance towards the floor or the seat, depending on which it is mounted.

Statistics have proven, beyond doubt, that these pretensioners greatly reduce injuries and particularly the possibility of fatal injuries in a car crash.

Now, with cars that are equipped with these devices, all we have to remember is to "belt up" when we get into our car. The rest is all automatic.

All collisions of any consequence will trigger the seat belt pretensioners, thereby dramatically reducing the potential for a serious injury.