On 21/10/2018 19:17, TMS320 wrote:

On 21/10/18 16:39, JNugent wrote:
On 20/10/2018 23:15, TMS320 wrote:

...I don't know how much is mandatory or voluntary.

That is as one might have suspected.
It didn't stop you offering comment on it.

No reason why not. Why does knowledge of the proportions matter?

For most purposes, it doesn't.

But it matters when one says that "the authorities" require the use of
hi-viz.