To make a **left turn**, it is essential to ensure there is **sufficient visibility**. This is crucial because it allows you to see if vehicles are coming from the opposite direction and assess whether it is safe to perform the maneuver without the risk of collision.

- **Insufficient visibility**: In situations where visibility is limited, such as in **sharp curves**, **crests**, or adverse weather conditions like **fog** or **heavy rain**, it is prohibited to make a left turn. The lack of visibility prevents you from seeing approaching vehicles in time, increasing the risk of accidents.

- **Road conditions**: On roads where you cannot see clearly, such as in **tunnels** or **level crossings**, it is also prohibited to perform this type of maneuver. The reduced visibility in these places makes the turn dangerous.

Therefore, whenever there is not sufficient visibility, you should not make a left turn to ensure road safety.