Diagram 555.1 is placed on carriageways that have a depth of water next to them that poses a danger to road users. The water could often be covered by the verge or plants which may make road users believe it is firm ground.
Material: R2/RA2 reflective overlay on aluminium composite backing
10.3.2. The water course sign, diagram 555.1 (S2‑2‑41, see Figure 10-8), is intended for locations where a road runs alongside a water course of sufficient depth to be a danger if a vehicle leaves the carriageway. This may be important if the water surface cannot easily be seen, e.g. because of obscuration by vegetation, or if the road is liable to flooding and there is difficulty in distinguishing between carriageway and water course. A sign is not necessary if the road edge is kerbed or if a safety fence is provided. Where the risk is to vehicles parking alongside a water course, e.g. at a quayside, diagram 555 will be more appropriate.