Interoperability is the ability of different systems, technologies or organisations to work together. This is usually based on compliance with common standards. In the field of technology, interoperable systems are also referred to as compatible.

Interoperability in public transport means that passengers can use a single ticket to access various transport services. For example, they can use their annual travelcard to travel by train, S-Bahn, bike-share scheme and local tram. However, it is also a prerequisite for cross-border travel that is as seamless as possible. This applies both between fare networks and between federal states, or even across national borders.

Without interoperability, they would have to buy a new ticket for every mode of transport on their journey. Even when changing from one bus route to another. Because this is the opposite of attractive public transport, interoperability has long been a key objective of (((eTicket Deutschland – even long before the D-Ticket existed. 

But since the introduction of the Deutschland-Ticket at the very latest, all systems must be interoperable. After all, passengers rely on tickets purchased in Bremen being accepted in Passau just as they are in Frankfurt or Rostock.