Since 1964, the interchange code has been the first and second digit of the twelve-digit wagon number on the side wall of a railroad wagon. It was defined by the UIC and the Organization for the Cooperation of Railways as binding for the member railroads. The main contents are the transition capability, the track gauge and the ability to change gauge during operation with wheelset changes or by means of gauge change wheelsets, divided into passenger and freight wagons.
The basic structure of these two sections is as follows:
- Freight wagons: range 00 to 49 and 80 to 89
- Passenger coaches: range 50 to 79
- Locomotives and railcars: range 90 to 99