Department of Transport, Traffic Signs Manual : Chapter 4… (2013)
“ However, account should be taken of visual obstructions en-route e.g. a rock outcrop might hide sheep wandering onto the road, necessitating a sign at that point. 18.3 On motorways or other roads with grade separated junctions where the hazard might extend over a long distance, (e.g. wild animals) the warning sign with a plate to diagram 570 should be repeated after every access slip road, or, if this distance would be excessive, at intervals of approximately five miles. Each plate should show the distance remaining to the end of the hazard. ”
