In railway signalling, a token is a physical object which a train driver is required to have or see before entering onto a particular section of single track. The token is clearly endorsed with the names of the section it belongs to. A token system is more commonly used for single lines because of the greater risk of collision in the event of a mistake being made by a signaller or traincrew, than on double lines.
Until the late 20th century, the token system was standard on British single-track lines and it still remains on a number of lines there as well as elsewhere, such as the line between Girvan and Stranraer in south west Scotland. Traditional token systems are also in use on heritage railways in Britain.