The Oyster card may have been inspired by Hong Kong's transport system, which uses the similar Octopus card. As with the Octopus card and other pay-as-you-go smartcards, also notably in Japan, there is the potential for future expansion of the Oyster card to act as an e-money payment system.
Travellers touch the card to a distinctive yellow circular reader (a Cubic Tri-Reader) positioned on automated barriers at London Underground stations to 'touch in' and 'touch out' at the start and end of a journey (contact is not necessary, but the range of the reader is only a centimetre or so). Tram stops and buses also have readers, on the driver's ticket machine or, in the case of articulated buses, near the other entrance doors as well. Oyster cards can be used to store both period travelcards and bus passes (of one week or more), and a pay-as-you-go balance.
The system is asynchronous with the most up-to-date balance and ticket data held electronically on the card rather than in the central database. The main database is updated periodically with information received from the card by barriers and validators. Tickets purchased online or over the telephone are "loaded" at a preselected barrier or validator.
Image 4The multi-level junction between the M23 and M25 motorways near Merstham in Surrey. The M23 passes over the M25 with bridges carrying interchange slip roads for the two motorways in between.
Image 13Sailing ships at West India Docks on the Isle of Dogs in 1810. The docks opened in 1802 and closed in 1980 and have since been redeveloped as the Canary Wharf development.
Image 25Arguably the best-preserved disused station building in London, this is the former Alexandra Palace station on the GNR Highgate branch (closed in 1954). It is now in use as a community centre (CUFOS).
Image 34The newly constructed junction of the Westway (A40) and the West Cross Route (A3220) at White City, circa 1970. Continuation of the West Cross Route northwards under the roundabout was cancelled leaving two short unused stubs for the slip roads that would have been provided for traffic joining or leaving the northern section.
Image 43London Underground A60 Stock (left) and 1938 Stock (right) trains showing the difference in the sizes of the two types of rolling stock operated on the system. A60 stock trains operated on the surface and sub-surface sections of the Metropolitan line from 1961 to 2012 and 1938 Stock operated on various deep level tube lines from 1938 to 1988.