Essex police stop cyclists for riding without lights, high-vis or helmets

@eschelar

You raise a very valid objection to the post you quote, but your own analysis is equally simplistic!

For starters, if you don't completely stop the movement of the car (as you likely won't unless you are obese enough to merit a Daily Mail hate-piece all of your own) then that energy will be transferred to your kinetic energy, and either the rapid acceleration will in itself do something very nasty (particularly if its exclusively your head that experiences it) or you'll then hit something stationary and absorb that energy in the end anyway.

And then there's the issue of the brain bouncing around inside the skull, even if the helmet reduces the impact damage to that skull.

Obviously the physics of helmets and impacts is very complicated but the original comment doesn't seem to be any worse a simplification than yours.

Anyway, I wear mine very much in the spirit of a lucky rabbit's foot. I remain convinced that the one time I set off without it will be the time something bad happens!

fret wrote:

It should be compulsory to knock off cyclists with no lights as well.

What do you think should be the penalty for drivers who break Highway Code paragraph 126?

"Stopping Distances. Drive at a speed that will allow you to stop well within the distance you can see to be clear. "

Fret, I was hoping for a reply.

eschelar wrote:

"eg the helmet gets you 50 - 100 joules of impact protection. Get hit by a smart car doing just 22mph (10 m/s) and the impact is of a magnitude of 40,000 joules."

Just thought I'd point out that this is faulty physics.

Impact is based on inertia and is relative, so both objects' mass must be considered.

While 40,000 joules sounds like atom-smashing force compared to 50 joules, think what happens when a car runs into a feather. It floats away unharmed and is NOT pulverized into its constituent molecules.

Similarly, while the force of the car might be 40,000 joules, the mass of your head is *significantly* less than the mass of a car. If the relative speed is 22km/hr, and your 40,000 joules represents a 2000lb car, but your head weighs 10lbs, what you're actually saying is that the head impact is 200 joules. In order for the 40,000 joules to apply, your head would have to be able to completely stop the motion of the car. That would be a factor if your head was caught between the bumpers of two cars or something, but in most cases, your head will just bounce off, encountering only enough energy to modify the movement of your head.

Which sounds like a 22km/hr collision would cause heads to explode like watermelons all over the place *EVEN WITH HELMETS* and is clearly totally ridiculous.

There are so many other factors to consider such as how directly the force is applied to your head and if you had already started to change your movement by the time your head made impact. Plus the fact that the helmet's function is to cushion and that means to increase the amount of time required to affect the movement of the head.

A force of 200 joules might be enough to scramble a person's head, but if it resulted in a change of motion taking place over a period of time 4 times as long, it might be just fine.

It's true that helmets are not helpful if they are impacted with enough force to blow them into confetti, but they will still reduce the potential for damage even in those circumstances.

I've seen people have collisions that shredded their helmets but went otherwise unscathed. And speeds were significantly higher than 22 km/h.

never read so much psuedo scientific voodoo in my life.

the reason why helmets spit and break apart is because they haven't worked not because they have. Just rto recap on how helmets are supposed to work. The styrofoam is designed to compress and therefore absorb some of the energy of the impact. That works up to around 100 joules on the very best brand new helmets. (the British, Euro and US standard is 50).

when a helmet is impacted by substantially more force than this it will fail. The strofoam does not compress properly and absorb impact it compresses much faster than 1/1000th of a second transferring the impact and spitting the styrofoam. This has happened to me crashing whilst mountainbiking.

Anyone that says they were protected by a helmet that spit or cracked doesn't understand how the helmet is supposed to work and therefore doesn't realise that their helmet just failed to protect their head and was overwhelmed.

And there some other junk in there as well. Your head my way 10lbs but it's connected to your body so doesn't bounce away independently.

Physics books are available from all good bookshops.

wwfcb wrote:

Coming from a cyclist, some of the comments are so over dramatic, ridiculous or people just get wound up over the slightest matter.

People are getting wound up over continuous victim-blaming. In the last 3 months we've had Boris Johnson respond to 6 deaths in 2 weeks by complaining about headphones, Operation Safeway fining a much greater proportion of cyclists while ignoring drivers on phones, the Met stopping cyclists without high vis and helmets, and now Essex Police doing the same.

This is why people are feeling harassed. The police should focus on the cause of the actual danger, not those put into danger while acting perfectly legally.