This is obviously the thread to report an experiment I did some years ago.
Because cycle helmets are not tested with regard to the protection they would provide if in collision with another vehicle, I was interested in the relative protection given by different materials when struck by a lump of sharp metal. Now I don't have a test rig, but I did have a helmet that had been left around by someone who didn't want it any more. I also had a box of tissues.
I took the seatpost out of my (then one and only) bicycle (leaving the saddle attached as a convenient handle) and, on a tarmac surface, struck the helmet with the end of the seatpost. To my horror, it penetrated easily.
I repeated the experiment with a box of tissues. Imagine my surprise when I discovered that the box of tissues completely protected the underlying tarmac from contact with the sharp metal!
Ever since then, I have worn a box of tissues strapped to my head. It provides more protection than a cycle helmet and therefore anyone who does not wear a box of tissues strapped to their head is an idiot (and I have the evidence to prove it). I shall campaign for it to be public policy that no cyclist with any injury whatsoever be treated with my tax money, unless they were wearing a box of tissues (in an appropriate place) when the injury occurred. In order to be consistent of course, the campaign will also ensure that the same is in place for pedestrians, car drivers, lorry and bus drivers ....