[SystemSafety] Bicycle Helmets

[Mike Ellims]

I suspect that this  boils down to a few simple things;

 

Helmets are designed to absorb a certain amount of energy, once it’s done doing that it can’t absorb any more and the impact is delivered directly though to the head. Kinetic energy being what it is, once the speeds go beyond a critical threshold wearing a helmet doesn’t make any significant difference;  1/2mv^2 rules – whether you like it or not.

 

It also depends on what you hit, hitting a flattish surface is better than hitting something with a hard edge such as the  curb.

 

It also depends on the sequence of events  i.e. hitting headfirst is not good, but hitting with a shoulder will absorb much of the initial impact. It also helps if you slide as energy is dissipated over a longer period of time.

 

Bike helmets are much like cars which are designed for the most statistically common accident, i.e. frontal impacts at 50 kph and side impacts at around 18 kph. This doesn’t mean the car will protect you in a collision at 150 kph (1/2mv^2 again).

 

 

From: systemsafety-bounces at lists.techfak.uni-bielefeld.de [mailto:systemsafety-bounces at lists.techfak.uni-bielefeld.de] On Behalf Of Matthew Squair
Sent: 15 October 2014 20:30
To: Peter Bernard Ladkin
Cc: systemsafety at lists.techfak.uni-bielefeld.de
Subject: Re: [SystemSafety] Bicycle Helmets

 

Likewise I have a bicyclist friend who was hit by a car and her helmet saved her from severe brain trauma. 

 

This was her second bad concussion from riding within the space of a couple of months, and as we found out the only thing the brain likes less than being shaken vigorously is having it done again. 

 

Fuzziness of the data notwithstanding, if we agree that helmets provide say '-x' degree of risk reduction, but in the two populations the proportion of injuries is still roughly the same, then we could conclude there must be some source of additional risk equal to 'x' that helmeted riders are exposed to? If so what is that risk? Or am I missing something?


Matthew Squair

 

MIEAust, CPEng

Mob: +61 488770655

Email; Mattsquair at gmail.com

Web: http://criticaluncertainties.com


On 15 Oct 2014, at 6:52 am, Peter Bernard Ladkin <ladkin at rvs.uni-bielefeld.de> wrote:



On 2014-10-15 00:01 , David Crocker wrote:



I have some indirect experience of the value of cycle helmets.


David's story is similar to what happened in one of the two incidents to my friend who wrecked two
helmets and her jaw, but in her case it was a lamppost base.

That's the puzzle. The value of helmets is obvious - many of us seem to know some one or more whose
lives have been saved - but apparently not from the numbers.

PBL

Prof. Peter Bernard Ladkin, Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany
Tel+msg +49 (0)521 880 7319  www.rvs.uni-bielefeld.de




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