When a **car breaks down** on the road, it is important to **signal the danger** to warn other drivers. On roads with **more than three lanes**, only **one pre-warning device** should be placed. This is because on these roads, traffic is denser and faster, and a single device is sufficient to alert drivers to the presence of a stopped vehicle.

- **Pre-warning light**: It is a yellow light placed at the highest point of the vehicle so that it is visible from afar. This light is mandatory and is used to indicate that the vehicle is stopped due to an emergency or breakdown.


- **Warning triangles**: Although they are not mandatory on roads with more than three lanes, they can be used as an additional safety measure. They are placed 50 meters from the vehicle and must be visible from 100 meters away.

In summary, on roads with more than three lanes, placing a single pre-warning device is sufficient to ensure safety and warn other drivers of the situation.