On ÖBB trains, infants travel free of charge and without a ticket. 

• On local, long-distance trains and ÖBB night trains infants must only travel with an adult. Infants can share a sleeping berth or couchette with the person who is accompanying them on night trains. Infants can be accommodated in gender-specific compartments, whether boys or girls. 
• Children on night trains must have their own sleeping berth or couchette.