Archive | March, 2015

Lies, Damned Lies and Flight Safety Statistics

25 Mar

You could be forgiven – if you’re careless enough to rely unquestioningly on popular academic sources or the BBC for news – for thinking that air travel is the safest form of transport, and is getting safer by the year.  If you were about to book a holiday within Europe, this might help ease your mind after hearing about the horrific Barcelona-Dusseldorf crash. You might even feel so safe that you rushed to book a seat while they were going cheap.

At a push, you might even consider booking seats for your children and loved ones because of those safety assurances.

But you’d be wrong.  Here’s how the con works.

Excluding Inconvenient Data

The BBC article I link to above claims that 2014 was the safest year ever for flying.  And then adds in the caveat that this applies only if the still-unexplained disappearance of Malaysian Airlines Flight MH17 is taken out of the statistics.

Why would you exclude one of the most highly publicised global news events of the year from statistical analysis?

Perhaps because you were using statistics supplied by a company that is actually a consultancy to the aviation industry, despite the BBC article referring to it by the nice, neutral and non-commercial sounding term ‘flight safety analysts ‘.  Or, possibly, because considering the passengers of MH17 as fatalities would mean that in 2014 air travel became more dangerous than it was the year before.

Or, perhaps, because you were operating with a set of definitional exclusions that conveniently made flying look much safer than it really is.  The article from The Conversation that I’ve linked to above, which argues that flying is ever so safe and that the public are getting themselves all scared over nothing, actually explains nicely how the exclusions work:

According to the Aviation Safety Network, of aircraft carrying more than 14 passengers and excluding sabotage, hijacking, and military accidents, in 2014 there were 20 crashes accounting for 692 fatalities – one of the lowest accident rates on record, even if the number of casualties is up on recent years, the highest since 2010. [my italics]

That’s a bit like imagining a world where terrorism, military aviation, business jets, helicopters, airshows and disgruntled ex-employees with access to Stanley knives don’t exist.

Obviously – and sickeningly – if it should happen that the investigators looking at the Barcelona-Dusseldorf crash discover that the cause was sabotage or terrorism rather than malfunction, then this crash will also magically disappear from the statistics quoted by Air Safety experts.

Measuring the Wrong Things

Intuitively, you’d expect an ‘expert’ telling you that flying was safe would be using a measurement schema that made some kind of sense.  He wouldn’t, for example, compare flying with walking on an accidents-per-mile-travelled basis.

Because that would be really stupid.

But you’d be wrong.

The only measure by which air travel is safer than all other forms of travel is when you analyse it by miles per fatality.  Using this same flawed logic would mean that space travel – involving whizzing round the Earth many times over in each mission – could conceivably be regarded as even safer than air travel.

Luckily, there’s other ways of measuring the relative safety of different modes of transport.  You could use accidents per journey, or accidents per hour of travelling time.  Somebody’s been considerate enough to do this already.  Kudos to Roger Ford and Modern Railways magazine.

Whilst the stats here are from 2000, you can see from the tables provided that air travel – measured by either journeys made or hours spent travelling – is very far from being the safest means of transport:

billion km billion journeys billion hours
Air 0.05 Bus 4.3 Bus 11.1
Bus 0.4 Rail 20 Rail 30
Rail 0.6 Van 20 Air 30.8
Van 1.2 Car 40 Water 50
Water 2.6 Foot 40 Van 60
Car 3.1 Water 90 Car 130
Pedal cycle 44.6 Air 117 Foot 220
Foot 54.2 Pedal cycle 170 Pedal cycle 550
Motorcycle 108.9 Motorcycle 1,640 Motorcycle 4,840

These figures are likely to vastly overstate the risks of cycling, motorcycling and walking.  Maybe I’ll go into the reasons for that another time, and what that says about the limits of using statistics rather than words.

But for now…

 

The Obvious Conclusion

You are much more likely to arrive in one piece, journey by journey, if you take a bus or a train rather than a plane.

There is an immensely profitable industry that depends on you being convinced that air travel is safe – or even that it’s the safest form of travel going.

But it isn’t.

In fact, by these measures, from all of the means of transport you are likely to choose between for a journey of significant length, air travel is the most dangerous.

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