In message , Adrian
writes
So - and I'm only going with this because I'm thinking about the
practicalities - all bikes should have mudguards, racks, or some kind of
frame to attach the plate to?

Is there anything wrong with the saddle post? Or a bracket off one of
the rear frame members?

Saddle post is out as luggage on rack often obscures it. Could fit one
to the back of the luggage rack (in my case). Many people don't have
racks, and attaching anything big to the RHS of the rear frame either
sticks out too far or obstructs pedalling.
Could make it of something flexible so it would flick back if struck.

How big do you want these to be? Same as a car/motorbike? Big enough to
be seen and reported if going through a red light :-)

Some-one mentioned the Dutch having to license their bikes, but I've
never seen anything that looking like one on the hundreds outside the
RAI station in Amsterdam.


--
Martin @ Strawberry Hill