On 24/02/2019 11:55, GB wrote:
On 23/02/2019 19:27, Simon Jester wrote:
On Saturday, February 23, 2019 at 12:49:54 AM UTC, MrCheerful wrote:
https://www.theargus.co.uk/news/1745...afety-warning/


What evidence do you have to show a cycle helmet would have made any
difference?

Research shows cycle helmets can only absorb 70 joules before failing
and it takes around 1000 joules to crack a human skull.

How many joules does it take to cause a catastrophic bleed on the brain,
though?

I'm not sure what you mean by 'before failing'? Does that mean the
helmet cannot absorb more than 70 joules altogether? Or it cracks but
still absorbs some of the impact?

The head has potential energy before a crash. If it freefalls to the
ground, that will contribute to a vertical component of kinetic energy
when it hits the ground. 5kg falling 1.8m has an original PE of 88J and
hits the ground at 12.5mph.

It should be noted that the head has the same potential energy when
riding a bike as when walking so I don't understand why riding a bike is
considered to need special treatment.

In the DfT's "Reported Road Casualties Great Britain: 2016" it says:

"The pattern for pedal cycles is an interesting one: the overall
casualty rate of around 5,400 casualties per billion miles cycled is
close to the motorcycling casualty rate, whereas the fatality rate of
29.5 per billion miles cycled is much closer to the pedestrian rate"

The figure given for pedestrians is 34.5 fatalities per billion miles.

Clearly a helmet has a tiny bandwidth - it can't do anything about the
worst injuries (or, if it does, it would be clear evidence that
pedestrians should use them) and it won't move the less severe off the
chart.

And clearly helmets vary.

....above a minimum in standards that specify the vertical drop test.