Humps for 300 yards' Inc Arrow Supplementary Plate - Post Mount Dia. 557.3 R2/RA2This supplementary sign is placed on routes that lead off onto roads with speed humps. It is installed alongside sign face 557. 1 and warns drivers that if they turn onto a route there will be speed humps for a set distance. The direction and distance described on the sign can be varied, as can the text size to reflect the route the sign is installed on. If you need any other variations that cannot be selected above please call for pricing. When