2012 February

Just how safe is cycling?

If you live in Australia, it would be pretty easy to assume that cycling is a high risk activity.  Just look at the at-hand evidence a typical person might see:

  • The government passes a law requiring you to wear a helmet regardless of where and when you ride in public,
  • Cycling seems to be a sports activity most appealing to men aged 20-45 years old who dress like pros and ride $10,000 bikes,
  • The media keeps telling us just how dangerous it can be.

But what about facts and hard data?  Absolute numbers are easy to come by.  The national Fatal Road Crash Database tells us that around 35 cyclists are killed each year compared with over 1500 for all road users.  Hardly enough to justify mandating helmets for cyclists but not all road users it seems.

But of course there are more motorists in Australia than cyclists.  How do we make a meaningful comparison between the two, or the fact the horses kill more Australians every year than bikes do? To assess risk we need to examine exposure, otherwise we will be committing the base-rate fallacy when comparing activities.  Sadly, Australia doesn’t track exposure data for cyclists so the best we can go on is modal share information from the 5-yearly census (but of course this lack of data didn’t stop our government passing mandatory helmet laws in the first place).

Europe however, does provide the data necessary for a meaningful comparison.  In 2003, they compared the safety performance of all road, rail, sea, and air transport modes both by distance travelled and exposure time.  The results are illuminating:

  • Mass transport is many times (often orders of magnitude) safer than all forms of private transport,
  • Driving to the airport is almost twice as dangerous as flying,
  • Driving is safer than cycling.

Two points are worth noting about this last claim.  Firstly, the data doesn’t take into account the source of the danger.  In Australia for example, over 90% of cycling deaths involve a motor vehicle meaning that cycling its self is safer than driving, but cycling on roads is not.  Secondly, the absolute risk of cycling (in fact all modes of transport) is tiny.  As in an expected fatality rate of 75 per 100 million hours of exposure tiny.  Or to put it another way:

You’d have to cycle 24hrs per day for over 150 years for each expected fatality.

Or at a more normal average of 1hr per day, it would take over 3500 years for each expected fatality.

Do you still think helmet laws are necessary? If so, please let me know just how many more hundred years of continuous cycling one would need before the risk is low enough.

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