The **high beam**, also known as the **main beam**, is a powerful white light used to illuminate long distances in front of the vehicle. This light is mandatory for all cars and optional for mopeds. Due to its power, it can dazzle other drivers.

One of the functions of the high beam is to **warn of an overtaking**. When a driver is going to overtake another vehicle on a road outside a town or city, they can use this light as an alert signal to inform the driver being overtaken. This helps to prevent possible accidents by ensuring that the driver being overtaken is aware of the maneuver that is going to be performed.

Therefore, the high beam is used as a warning signal to indicate to other drivers that an overtaking maneuver is going to be performed, thus ensuring safer driving.