By SCOTT MacLEOD
In a high-speed car crash, the chance is high that your brain will slam into the front of your skull and then bounce back, rattling like dice in a cup.
All the banging about will cause the brain to swell, often forcing it to squeeze into the brain
stem.
When St John Ambulance paramedic Neville Montefiore arrives at a crash to find people already dead, it is often because of brain swelling.
The other quick killer is when a victim's aorta rips apart and the patient bleeds to death.
Mr Montefiore and his Northland colleagues deal with the graphic side of a message everyone has heard - the faster we go, the bigger the mess.
Speed has become a political hot potato during the past nine months. Road safety officials have suggested cutting the limit from 100 km/h to 90 km/h as part of a plan to trim the annual cost of road smashes from $3 billion to $2 billion.
Many motorists are indignant at the idea, but how many lives would it save?
The Land Transport Safety Authority estimates that each drop of 1 km/h in speed on the open road will slice 3 to 5 per cent off the road toll - about 20 lives for the first 1 km/h.
Despite years of advertising, speed still contributes to one-quarter of all road deaths - and half of those deaths occur on the open road.
The LTSA says each year about 140 people are killed and a further 2350 hurt in crashes where vehicles are going too fast for the conditions.
The key part of that statement is "too fast for the conditions," because it is common for motorists to drive dangerously fast without breaking the speed limit.
One reason is that the highway limit of 100 km/h is too fast for sharp rural corners - a legacy of the early days of road building, when linking A and B was enough of a problem without doing it in a straight line.
LTSA engineer Richard Bean says the idea that driving at the speed limit is safe is "totally misfounded." Factors such as traffic, corners and bad weather should all make drivers slow down.
Other studies have found that a motorist is twice as likely to die in a crash at 120 km/h than at 100 km/h, and four times as likely at 130 km/h.
The effects are more marked for pedestrians. The death likelihood when hit by a vehicle increases from 5 per cent at 30 km/h to 40 per cent at 50 km/h, 70 per cent at 60 km/h and 96 per cent at 70 km/h.
But myths also surround speed.
Perhaps the most common is that when vehicles travelling at 100 km/h collide head-on, they will suffer the same damage as if they each hit a solid wall at 200 km/h.
Actually, the effect on each vehicle is the same as if it hit a wall at 100 km/h, because the force of a head-on smash is spread over both vehicles.
A senior physics lecturer at Auckland University, Dr Graeme Putt, said that doubling the speed of a vehicle would quadruple its kinetic energy, or impact force.
But the deceleration effects would only double.
"The mayhem to the car is energy, but in an accident you are probably more concerned with the patient, which is deceleration forces."
The good news is that traffic surveys show a tiny reduction in speed on the open road. Last year, the average was 101.4 km/h. In the previous four years, it was between 101.6 km/h and 102.3 km/h.
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By SCOTT MacLEOD
In a high-speed car crash, the chance is high that your brain will slam into the front of your skull and then bounce back, rattling like dice in a cup.
All the banging about will cause the brain to swell, often forcing it to squeeze into the brain
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