Compulsory cycle helmets - breakfast news item

[Androcles]

Sounds like you know far more than me, so this is interesting. Let's be clear; the point of my post was that the square of the speed is a better simplistic gauge, when hitting a solid object, than taking 12mph off any impact speed.

You are right, the 12 mph reduction only works at one speed.  The speed squared factor in the energy means that the amount of effective impact speed reduction will drop off with increasing impact speed.

In reality, of course, crashes are very complex processes (so much so that I'm not sure that anyone has satisfactorily modelled them), and way beyond my ability to calculate. Many real crashes would involve bouncing along the road, and momentum would then play a part as mrcharly says - but most people seem to be thinking of colliding with things (mostly cars) when they talk about helmets for protection, whereas even the BHSI then pretty much rule out helmets as useful.

Again, dead right.  Any crash is going to be difficult to reconstruct in a mathematical model.  No, make that very difficult indeed.  Until humans are equipped with accelerometers and data loggers  we are still going to be making educated guesses as to exactly what the inputs are.

[Eccentrica Gallumbits]

Yesterday my upstairs neighbour was wearing his bike helmet, except it had no plastic shell, so it was just the polystyrene inner and straps.

[ScumOfTheRoad]

At the risk of keeping a flame war going, I don't agree with Androcles poitn re. modelling crashes.
I have installed supercomputers for a jet engine manufacturer - they are well on the way to creating virtual crash tests, and certainly run 'blade off' tests with finite element software many times before running the expensive real engine test mandated by the US authorities.

FEA simulations of motor vehicle crashes are regularly done. Quick Google turns this up
https://lirias.kuleuven.be/bitstream/123456789/266797/1/A+TRANSIENT+FINITE+ELEMENT+STUDY+REVEALS+THE+IMPORTANCE+OF+THE+BYCICLE+HELMET+MATERIAL+PROPERTIES+ON+HEAD+PROTECTION+DURING+AN+IMPACT.pdf

It at least shows that FEA simulations are being used in this field - you are of course welcome to argue about the methodology, or how far to trust simulations like this.

[mrcharly-YHT]

I'm happy with the way that simulation has been done.

However, it models impact on a fall of 1.5m and at that shows a deformation of 80% of the foam.

Differing speeds are not addressed in the model.

Obviously, they are looking at the impact resulting from the fall to the ground, and the forward velocity of the cyclist has little influence on that.

That's a lot lower than when riding at 30kph and striking a vehicle, kerb etc.

[ScumOfTheRoad]

Mrcharly, your point taken. Any realistic simulation should be with a moving vehicle.

[Jaded]

I'm intrigued in that paper that "69–93% of fatal bicycle accidents are due to the head injuries (Guichon, 1975; Oström, 1993). Most of these victims were not wearing a helmet."

Both these figures seem high, and there is no indication of what the general helmet-wearing figure in the population is either - nor any indication of the rate of deaths per kilometre cycled.

[mrcharly-YHT]

It sounds likely to me. Modern medicine is pretty good at treating massive trauma to other bits of the body.

My father and I fallen off or been trampled by galloping horse lots of times; I reckon that's probably worse than most falls when cycling. We usually walked away. When dad fell and hit his head, he nearly died.

[Wendy]

I'm intrigued in that paper that "69–93% of fatal bicycle accidents are due to the head injuries (Guichon, 1975; Oström, 1993). Most of these victims were not wearing a helmet."

Both these figures seem high, and there is no indication of what the general helmet-wearing figure in the population is either - nor any indication of the rate of deaths per kilometre cycled.

It seems unlikely to me - Guy Chapman often used to quote how a large proportion of cycling deaths had such massive trauma that death would have resulted even if all head trauma was magically taken out of the equation.

[mrcharly-YHT]

Who is Guy Chapman? Do you have a source for this?

although now I think of it, for the 'cyclists crushed against railings' type accidents, this Chapman chap is probably right.

[mattc]

guy chapman helmets - Google Search

[drossall]

Even if the figures are representative then, as noted, the percentage with fatal head injuries is not the same as the percentage who would be saved by preventing head injuries. Nor do the figures quoted indicate whether any conceivable helmet would have helped anyway. The evidence on a population level appears to be that it does not.

[rogerzilla]

Yesterday my upstairs neighbour was wearing his bike helmet, except it had no plastic shell, so it was just the polystyrene inner and straps.

A lot of them used to be like that by design.  Of course, they snag the road when you fall and break your neck.

[David Martin]

It at least shows that FEA simulations are being used in this field - you are of course welcome to argue about the methodology, or how far to trust simulations like this.

For that one, about as far as I could throw it. Static impact with a ventless helmet?

But yes, such simulations are interesting. They don't address the 'just because something can be done, does it need to be done?' question.

..d