The **U-turn** is a maneuver that allows you to turn around to drive in the opposite direction on the same road. However, there are specific situations where this maneuver is prohibited for safety reasons.

- **Tunnels**: It is prohibited to make a U-turn in tunnels. This is because tunnels are enclosed and narrow spaces where visibility is limited, increasing the risk of accidents when performing complex maneuvers like a U-turn.

- **Curves and hill crests**: In these places, visibility is reduced, making it dangerous to perform a U-turn.

- **Adverse weather conditions**: In situations of fog or heavy rain, visibility decreases, increasing the risk of collisions.

- **Highways and expressways**: Although generally prohibited, it is allowed in places specifically prepared for it.

- **Level crossings and one-way roads**: It is also prohibited to make a U-turn in these places for safety reasons.

Therefore, it is crucial to respect these restrictions to ensure road safety and avoid dangerous situations.