You can decide for yourself whether a vehicle should be generally available for booking.
Path to the starting point: Infrastructure Building Management - Fleet Management - Vehicles
Select the desired vehicle from the list and click the Edit icon in the corresponding row.
If you want to make the vehicle generally available for booking, check the box in the Bookability section.
If you want to block the vehicle for booking, uncheck the box in the "Bookability" section.
Click Save in the toolbar.
The vehicle has been blocked or made available for booking.