Oyster card
Oyster card pay-as-you-go users must "touch in" at the start of a journey by London Underground or DLR, and "touch out" again at the end. The Oyster card readers automatically calculate the correct fare based on the start and end points of the journey and deduct that fare from the Oyster card. Pay-as-you-go funds are also used to cover any additional fares due from season ticket holders who have travelled outside the valid zones of their season ticket (see Travelcards above).