The London tube map become the first diagrammatic representation of an entire rail transport network in the world, the design is treated as the 'London classic design'. It became an iconic image of london mostly because of its pioneer diagrammatic design which has been used widely, not only as a map that uses as a travel guide, but also a piece of decorative graphic.
Since its first issue in 1931, the map has been a popular diagram, and because of its effectiveness as a travel guide, many transit authorities in other countries imitated the abstract diagrammatic design for delivering their own transport networks informations. The contribution of the tube map to information design as a excellent example for typographic design, color theory, the history of type design, lettering and general drawing, has been spread all over the world in the name of London. Thus, It has slowly become an icon for London.
The tube map is firstly print into card folder for the passengers to refer to, and afterwards it has been featured on T-shirts, postcards, and other products as souvenirs in London for the tourist to buy. It is also printed at the back of road maps for the convenience of the passengers to sought for travel information. With the map's popularity in the city and its existence everywhere, it slowly become an iconic image of London.