So lets write down the design and testing specification for a helmet that should protect a cyclist in a motor traffic accident. As it was your proposal, you have the honour of first draft. Of course part of the problem is we don't know whether its a problem of it not being protective enough, it making the head a larger and heavier target, or behavioural factors like risk compensation. So even if you have a perfectly protective helmet it may fail on the other two factors.
As a starting point though you might like to use Lewis Hamilton's helmet and look at how you would beef that up based on the comment from the UK's main helmet test house:
"In many legal cases I have studied where a cyclist was in collision with a motorised vehicle, the impact energy potentials were of a level that outstripped those that we use to certify Grand Prix motor racing helmets."
There you have it.... helmets will not be the only answer
We could simply beef up the standards to where they were twenty years ago when helmets offered far greater protection, do we remove the snag points that cause rotational injuries and can cause the helmet to come off in an impact.
Or we could take the adviceof the medical profession?
Headway the pro-helmet charity are quoting a paper from the British Dental Association which points out that 2/3 of head injuries in cyclists are facial ones and that the Dental Profession has a responsibility to ensure that helmet design offers greater facial protection
The dental profession could: play an active role in promoting cycle helmet use; support calls for the compulsory wearing of cycling helmets, particularly for children; press for modification of helmet design and standards to increase protection of the face.
So for a start should we be observing their advice and looking at full face helmets?
The other option is to look at the impacts and what can be done.
There are vehicles on the roads that are demonstrably going to cause greater injuries than others.
Should we also be looking at the design of vehicles and why some are allowed to be more unsafe than others?