It goes without saying that a law compelling protective equipment can only be justified if the activity being regulated is actually dangerous. Is this the case with cycling?
There are several ways to define dangerous, of course. Let's look at some of them:
Risk per hour is difficult to determine, but as far as we can make
out the risk per for cyclists is about the same as it is for
pedestrians. Failure Analysis Associates in America went
further: they computed that the fatality risk for cycling and being a
passenger in a motor vehicle were about the same, and both were lower
than the risk for walking alongside a road. But that is in the
USA.
Risk per mile is also about the same as for pedestrians. The
source for this is the DfT's transport statistics at
http://www.dft.gov.uk.
There's a summary at http://www.dft.gov.uk/pgr/statistics/datatablespublications/modal/tsgbchapter1passtrans1861.pdf,
but it does not tell the whole story.
According to DfT, then, for 2006 the risk per billion kilometres travelled was 36 fatal, 371 KSI for pedestrians, 31 killed and 527 KSI for cyclists. That is based on an average distance travelled of 39 miles per year by bike and 201 miles walking, for the entire population. If you compare these with the KSI figures for cyclists and pedestrians from STATS19 data - 2442 cyclists and 7051 pedestrians - you can cross-check the numbers by calculatring the population. The cyclist figures give a population of 74 million, the pedestrian figures 59 million. The latter is about right, so if you factor the cyclist figure down to match you end up with a risk ratio of 419:371 - which would make cycling just over 10% more dangerous than being a pedestrian.
But there's another problem here: the STATS19 data on which these
figures are based include all serious or fata injuries where the police
are called and which involve a vehicle on the roads. So any
cyclist collision - including rashing after hitting a pothole - where
the emergency services attent, will be counted. But a pedestrian
injury with no vehicle involved (such as tripping on a paving stone) is
not included. Trips and falls are the single largest cause of
injury admission to hospitals.
On top of that, the figures for exposure are recognised as being
terribly inaccurate, so much so that you probably can't trust them to
be right within a factor of two or three at best.
The inescapabe conclusion, once again, is that cycling is not
especially dangerous - unless you consider being a pedestrian to be
especially dangerous.
The risk posed by cyclists to others is extremely low. The
majority of cyclist miles are in areas where there are pedestrians, but
cyclists kill on average under one pedestrian per year - drivers kill
around seventy pedestrians
on the pavement every year, and over 3,000 people in
total. When cyclists are injured in car v. bike collisions the
car driver is usually at fault (in between 2/3 and 7/8 of cases
depending on your source)
Government figures show only a handful of cases of serious or fata
injury caused to pedestrians by cyclists in a year, and these are
masisvely outweighed by the numbers of pedestrians killed and injured on the footway by motor
vehicles. Pedestrians are at vastly more risk from motor vehicles
than from cyclists even when they are on the pavement. I have some more
thoughts about the politics of this.
Like pedestrians, cyclists are vulnerable to motor traffic, but unlike pedestrians, cyclists spend a lot of time on the roads in amongst that traffic. Between four and five times as many pedestrians are killed and injured by cars every year as are cyclists, which may indicate that cyclists are actually slightly less vulnerable, once exposure to risk is factored in.
One interesting fact is that cyclists are less likely than motor drivers to be to blame when they are hit, and are the most likely of all types of road users to be the victims of hit-and-run.Figures are hard to come by, and most of them are based on
guesstimates of varying accuracy, but it is quite hard to make a
compelling case for cyclists being at higher risk than
pedestrians. Why does nobody suggest compulsory walking helmets?
DfT have published a really interesting discussion of cycling
issues, you can read it at http://www.dft.gov.uk/162259/162469/221412/221549/227755/328843/pedalcyclistfsheet07.pdf
(it may move, it has moved before, if necessary this Google
search should find it)