The sign "Prohibition of overtaking single-track vehicles for multi-track motor vehicles and motorcycles with sidecars" indicates that vehicles such as cars and motorcycles with sidecars are not allowed to overtake single-track vehicles, which typically refer to bicycles or motorcycles without sidecars.

This sign is important for safety reasons; it helps prevent accidents in areas where single-track vehicles may be traveling slowly or unpredictably. By prohibiting overtaking, it reduces the risk of collisions and ensures that all road users can navigate the road safely. You must adhere to this sign and avoid overtaking single-track vehicles until you are outside the zone where this prohibition is in effect.