On a road with **three lanes in each direction**, it is important to know when you can drive in the left lane. Here we explain why the correct answer is that you can use the left lane **when the other lanes are occupied and it does not hinder the passage of vehicles driving behind**.

- **General rules for three-lane roads**: On two-way roads with three lanes, you should primarily drive in the right lane. The center lane is used for overtaking or turning left. However, the left lane should not be occupied unless necessary due to traffic conditions.

- **Traffic conditions**: Outside towns or cities, cars can use the left lane if traffic circumstances advise it, as long as they do not hinder other drivers. This means that if the right and center lanes are occupied, you can drive in the left lane, but it is crucial not to obstruct vehicles coming from behind.

- **Exceptions for heavy vehicles**: Some vehicles, such as trucks and vans that can carry more than 3,500 kilos, have additional restrictions and must primarily drive in the right lane, using the adjacent lane only when necessary and without occupying more lanes.

In summary, the use of the left lane on a three-lane road is allowed when the other lanes are occupied, as long as it does not hinder the passage of other vehicles.