In the standard case, all fare systems are independent, so that the total fare for a connection is the sum of fares per fare system. Transfer fares allow modeling of interactions. Like the initial fare, they are added to the ticket type's basic fare for the fare system.
The initial fare is only imposed for the first path leg and depends on the fare system of the first path leg. The transfer fare is calculated for each transfer, where a new ticket has to be bought. It depends on the fare systems of the lines, where the transfer is made.
Both components can be negative for modeling deductions. The resulting total fare of a connection is however greater or equal to zero.
Example:
Initial and transfer fares("Fare reference" of a fare system)
