Transfer (public transit)
A transfer allows the rider of a public transportation vehicle who pays for a single-trip fare to continue the trip on another bus or train. Depending on the network, there may or may not be an additional fee for the transfer. Historically, transfers may have been stamped or hole-punched with the time, date, and direction of travel to prevent their use for a return trip. More recently, magnetic or barcoded tickets may be recorded (as on international flights) or ticket barriers may only charge on entry and exit to a larger system (as on modern underground rail networks). Some public transportation systems allowing a rider to switch from one vehicle to another for free without paying an additional fare. A free transfer can be implemented by having both vehicles stop within the same fare control area, by issuing the rider a special ticket (also called a "free transfer") or by using an electronic smartcard system programmed to allow such transfers. Fare cards vastly simplify transfers, especially between different operators, since the transfer and payment (if any) is handled automatically by the card. Since transfers between services can significantly expand the effective range and coverage of another service, fare cards are often implemented specifically to improve a transit network's quality. References

Public transport fare collection