Which vehicles are not allowed to drive here?

This traffic sign means "No entry for motorized bicycles" (Mofas). Only motorized bicycles, also known as mopeds (with a speed limit of 25 km/h), are not allowed to enter here. Small motorcycles and light motorcycles are not covered by this prohibition and may enter if no other restrictions apply. You correctly identified that only motorized bicycles are forbidden. The rule to remember: this sign specifically restricts only mopeds—always look at the symbol carefully to know which vehicle category it applies to.