Monday, 25 March 2013

Shuttle safety record - not so bad

After casting asparagus last night at NASA for the safety record of their Shuttle program, I realised in the cold light of day that I had been a bit unfair.  In particular, I may have fallen into a well known psychological trap of risk-analysis - we tend to pay attention to spectacular accidents and this affects our behaviour in counter-productive ways.  Gerd Gigerenzer, a risk expert, estimated that, in addition to the 3,000 Shanksville, PA, World Trade Centre and Pentagon deaths, an extra 1,500 people died in cars (inherently dangerous) because they were illogically leery of flying (fundamentally safe) in the months after 9/11.

On reflection, I thought that a better statistic might be deaths per vehicle mile.  The Shuttle program cumulatively clocked up a pretty impressive mileage in 135 missions for a total of 21,158 orbits of the Earth.  As the Earth is, by definition, 40,000km in circumference, that totals about 850 million kilometers, resulting in 14 deaths, no serious injuries.  That's about 1 death per 60,000,000 km travelled.

In Ireland, there are about 1.5 million private cars.  The average annual distance travelled by each personal-stereo-on-wheels is supposed to be 10,000km.  The Irish Road Safety Authority struggles to keep the annual road death toll under 200.  Curiously, the injuries (minor, disabling, serious), which probably cost society more than the deaths are rarely remarked let alone weighed in the balance.  ANNway, the figures just enumerated indicate that the death rate on Irish roads is about 1 per 75,000,000 km travelled.

So I stand by my recommendation to travel by bus, but retract my implication that the Shuttle was outrageously more dangerous than other modes of transport.

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