**High beam headlights** or **main beam headlights** are very powerful and are designed to illuminate long distances in front of the vehicle. Due to their intensity, they can **dazzle** other drivers if not used properly.

- It is **not allowed** to use these lights when the vehicle is **stopped or parked**. This is because, when not in motion, there is no need to illuminate the road at a long distance, and the use of these lights could cause discomfort or hazards to other drivers.

- These lights are **mandatory** in certain conditions, such as on roads outside towns or cities at night or in poorly lit tunnels. However, when the vehicle is not in motion, these situations do not apply.

- Although they can be used to **warn of a danger** to other drivers, this is done intermittently to avoid dazzling, and it is not applicable when the vehicle is stationary.

Therefore, the **correct answer** is that high beam headlights should not be used if the vehicle is stopped or parked.