Opening Or Swing Bridge Sign Post Mount- 529 R2/RA2 (Face Only)The opening bridge ahead diagram is used in advance of bridges that lift or swing open. The bridge warning sign can be used with diagram 572 to warn of the "Distance Ahead" or a "Directional Arrow" from 573. If movement onto a bridge is controlled by wig wag signals, a plate displaying diagram 773 should be added. You will find this pole mounted sign in places where hump bridges are a hazard, commonly in country lanes where the turnings reduce the