Under The Microscope: THE DRIVER

 

Numerous investigations have been made by road research organizations and car manufacturers using dummies and actual corpses, together with sophisticated recording equipment and high-speed cinematography. These have establisheda detailed picture of the sequence of events in automobilecrashes. When the most common event - frontal impact - occurs, the unrestrained driver first slides forwards so that his legs strike the fascialparcel-shelf area, and his abdomen or lower chest contacts the lower edge of the steering wheel. The body then flexes across the steering wheel and begins to rise. The heavy head goes forwards, and there is flexion of the cervical and thoracic spines. The upward and forward component causes the head to strike the windscreen, the upper windscreen rim or the side pillar. The windscreen is often perforated by the head or face, and the whole body may be ejected through the broken glass, to land on the bonnet or even on the roadway ahead. Another factor causing injury is the intrusion of structural parts into the passenger compartment. Though modern cars are designed to maintain a rigid central passenger compartment, if the impact is gross, the engine or front-wheel assembly may be forced back into the seating area, intruding upon the driver. Similarly, the roof or front corner pillar (the so-called 'A'-frame) may cave in on top of the driver. One effect of column, engine, or gearbox intrusion may be to force the floor up and backwards against the driver's feet and legs. The control pedals also take part in intrusion, and, in the usual desperate braking and declutching, the reflex pressure of feet on rising pedals and floor may cause transmitted force up the legs and into the pelvic girdle. The steering column was formerly a more dangerous item for intrusion, being forced back to 'stab' or crush the driver's chest or abdomen. Modern design has reduced this danger by making the column telescopic, hinged or otherwise collapsible, but injuries still occur - sometimes from the wheel itself breaking and penetrating the chest. Additionally, the door may burst open and the driver, if unrestrained, ejected sideways onto the road, especially in a crash that has a roll-over component. In a rear impact, the driver is violently accelerated and, if no rigid head restraint is fitted to the seat, severe hyper-extension of the neck occurs, often followed by the sequence of deceleration events when the car is cannoned into the vehicle or other obstruction in front, causing the popular, if inaccurate name of 'whiplash'. In side impacts, the injuries depend upon the amount of intrusion of the driver's door and side panels. Restraint devices can offer no protection, though modern vehicles usually have strengthened side-impact bars built within the doors.

This range of traumatic events can produce the following lesions in drivers not wearing seatbelts or protected by airbags:

 

§  Impact against the fascia can cause abrasions, lacerations and fractures of the legs around knee or  upper shin level.

§  Pressure of feet on the floor, especially when it is intruded by the engine, can cause fractures anywhere from foot to femur. The leg can also be injured by violent contact with the fascia or dashboard and the hip joint may be dislocated posteriorly. 

§  Impact of the abdomen and chest against the steering wheel may cause severe internal injuries, usually rupture of the liver (50 per cent) and, less often, spleen (36 per cent). There may be bruising of the skin surface, but this is often absent even in the presence of severe internal injuries. Laceration of the skin is rare unless the steering wheel snaps and penetrates the trunk. Other steering-wheel lesions include bruising of the lungs, fractured ribs and sternum, cardiac contusionand haemothorax or pneumothorax or both. 

§  The most obvious injuries are ofren those to the face and head as a result of projection against and ejection through, the windscreen. The unrestrained driver rises and flexes forwards so that his forehead and skull are likely to contact the upper rimdof the windscreen, leading to lacerations. The face'frequently suffers multiple cuts from contact with the shattered safety glass. In most European vehicles the glass is of the toughened, not laminated, variety and, when broken, it shatters into small cubes with relatively blunt edges. These still cause superficial lacerations, often in short 'V-shaped' or 'sparrow-foot' patterns. In themselves they are not a danger to life, but indicate an impact sufficient to hurl the driver on or through the glass.

A more common thoracic injury associated with deceleration is the ruptured aorta. It may be associated with a severe whiplash effect on the thoracic spine, as the aorta is tethered to the anterior surface of the vertebrae where the distal arch joins the straight descending segment. Probably the most common reason for aortic rupture, however, is the 'pendulum' effect of the heart within the relatively pliable thoracic contents. When the thorax is violently decelerated, the heavy cardiac mass attempts to keep moving ahead and may literally pull itself off its basal mountings, the most rigid part of which is the aorta. Separation takes place at the point where the aorta is attached to the spine at the termination of the arch. The appearance of the aortic rupture is often of a clean-cut circular break, almost as sharp as if it had been transected with a scalpel. Sometimes there are additional transverse intimal tears adjacent to the main rupture, the so-called 'ladder tears', as they can resemble the rungs of a ladder. These may be present when no actual rupture has occurred and may be found as an incidental finding at autopsy. Sometimes they are deep enough to allow a local dissection of blood to seep into the intima, when death has not been virtually instantaneous. Rarely, a major dissection may lead to delayed death some hours or even days later. Though there is no steering wheel to impact into the chest, its absence also denies the slight protection offered to the driver in reducing the collision with the windscreen, perhaps by giving him something to brace against. Another factor may be that the driver gives his attention constantly to the road and so has momentary warning of an impending crash, compared with the passenger who may be oblivious of imminent disaster and fail to 'brace up' ready for the mpact. This may explain the greater number of skull fractures and brain damage in unrestrained passengers in Mant's series, the percentages being 55 per cent and 42 per cent, compared with 64 per cent and 53 per cent, respectively. However, these figures were compiled before seatbelts and airbags became commonplace or even mandatory.

During violent deceleration, unrestrained occupants in the rear are projected forwards and strike the back of the front seats, including head-rests where fitted. They may be thrown over the seats, striking and addmg further injuries to the front-seat occupants and may even be ejected through the windscreen, which is broken by them or by the people in front. In roll-over accidents, they share in the general trauma of being churned inside the passenger compartment, when multiple injuries can occur from contact with fitments, such as mirrors, door handles and window winders. Design changes have reduced these hazards by making handles smoother or countersunk and mirrors that easily snap off their mountings. Ejection is another common cause of death and serious injury in rear-seat occupants, a wide range of head, chest and limb injuries being seen.

 

As stated, many countries now have legislation making the wearing of front and rear seatbelts mandatory. Where no laws exist, persuasion seems to have little effect, in spite of the fact that it is uncontested that their-use reduces deaths and serious injury by a factor of 20-25 per cent, as seen in the Australian experience in Victoria and New South Wales. A similar reduction was attained in Britain after the introduction of mandatory laws. Not only did the death rate drop substantially, but facial injuries and especially eye damage was dramatically reduced.

Acknowledgements:

www.aived.nl    AIVD – @Erik Akerboom ©

www.politie.nl  Politiekorpschef  @Janny Knol©

www.politie.nl WEB Politie - @Henk van Essen©

 

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