Where:
On any road where a single carriageway (two way traffic sharing the same roadway) is about to divide into a dual carriageway or one way road.
These signs are commonly found on highways, main roads, or routes leading out of towns, where traffic will be separated by a median, barrier, or central reservation to allow vehicles in each direction to travel safely without interference.

Purpose:
To warn drivers that the single carriageway is ending and that they are about to enter a divided, one-way road.
This change improves traffic flow, reduces the risk of head-on collisions, and allows safer overtaking opportunities.
It also reminds drivers that while the road may become one-way, it does not automatically become a freeway, so intersections, side roads, and pedestrian crossings may still be present.

Action:
Prepare for the change in road conditions by choosing the correct lane for your direction of travel.
Be aware that overtaking will be safer once the dual carriageway begins, but continue to observe road markings and speed limits.
Maintain attention for intersections, pedestrians, or side roads that may still occur on the dual road.
Position your vehicle correctly within your lane to smoothly merge onto the one-way carriageway.
Observe signs and road markings that indicate lane usage, exits, or merging points.
Adjust speed if necessary to match the flow of traffic entering the divided road.
Drive defensively, watching for vehicles merging from the opposite carriageway or entering from side roads.