What is the maximum speed a vehicle may drive in a zone with this sign?

The sign you're looking at indicates a bicycle zone, allowing only cyclists to travel there, while the additional sign "Anlieger frei" means that residents (or those with a legitimate reason) are permitted to enter this area as well.

In a bicycle zone, motorists are generally prohibited from driving. It's essential to understand that these areas prioritize safety for cyclists and restrict vehicle access to protect them. If you're in a zone with this signage, you should be aware of your surroundings, yielding to cyclists and ensuring their safety while driving.

Overall, adherence to this zoning helps create a safer environment for non-motorized road users.