In rail transport, the paid area is a dedicated "inner" zone in a railway station or metro station barriers. A system using paid areas is often called fare control. Passengers are allowed to enter or exit only through a faregate. A paid area usually exists in rapid transit railway stations for separating the train platform from the station exit, ensuring a passenger has paid or prepaid before reaching the platform and using any transport service. Such design requires a well organized railway station layout.
The paid area is similar in concept to the airside at an airport. However in most cases entrance to the paid area requires only a valid ticket or transit pass. The exception is in international rail travel, where passengers must also pass through immigration control and customs to enter the paid area.