From another forum. I think this is worth repeating:
Hi folks.
Just a heads up to ask for your participation in signing an e-petition re; changing the rule relating to the use of the warning horn.
The petition calls for the reintroduction of using both tones at (W) boards in pursuit of safety for people using foot crossings.
Link here;
http://epetitions.direct.gov.uk/petitions/40379