A journey planner is a system that calculates a journey for a given request. It is able to accept requests directly from end-user services.

Austria, Czech Republic, Slovenia, Slovakia, Hungary, Romania are the starting countries that will benefit from the Danube Region Journey Planner as a service.
An open journey planner is a journey planner which follows the Standard for communication for distributed journey planning CEN/TS 17118:2017 (Open API for Distributed Journey Planning).
The development of an OJP information service requires participation of data owners, data suppliers, data aggregators, travel data and service providers, travel data publishers, and travel information service providers.