When a vehicle experiences a **breakdown on a dual carriageway** and cannot maintain the appropriate speed, it is important to act safely to avoid obstructing traffic. The **correct action** is to **drive to the first exit** where the road can be left. This is because:

- **Driving at an abnormally reduced speed** on a dual carriageway can be dangerous and cause traffic obstructions. Therefore, it is essential to leave the road as soon as possible.
- If the vehicle can still move, even slowly, the **right shoulder** should be used to reach the first available exit. This minimizes the risk of accidents and facilitates traffic flow.
- In case the vehicle cannot continue, it should be parked on the **right shoulder** or in a place where it causes the least possible obstruction, such as the median.

It is important to remember that, in emergency situations, the **hazard lights** should be turned on and, if possible, the **emergency warning light** should be placed to alert other drivers. Additionally, passengers should move to a safe place, wearing reflective vests if it is necessary to exit the vehicle.