See also my table showing in detail how the definition of an 'interchange' has varied over the years within the London Underground. This was a hand-out sheet at the meeting.
1. General evolution of the interchange in London
London 1924
Map of the London Underground published by the Metropolitan Railway Company. Shows all non-Metropolitan lines in the same colour, hence providing no indication of different lines or their interchanges. Until July 1933, the underground railways were operated by separate companies, who wanted to advertise their own services in their maps, but they had no commercial interest in other companies' lines.
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London 1909
Similar map issued by the London Underground Group in 1909. Lines are colour-coded, adding greatly to the intelligibility. Given that the LUG were producing maps of this design from 1908 onwards, it is curious that the Metropolitan Railway Company kept on churning out their dreadful maps throughout the 1920s.
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London 1909 (detail around Charing Cross)
Detail of the previous map, showing crudely drawn interchanges.
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London 1912 (detail around Charing Cross)
Slightly later map by the LUG, showing better defined interchanges.
London 1921 (detail around Charing Cross)
MacDonald Gill's map, showing the open circle symbol for an interchange, which has been used for the following eighty years.
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London 1921 (detail around Gloucester Road)
Shows the white bridges between interchanges.
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London 1923 (detail around Gloucester Road)
Slightly later Gill map, showing elongated white bridges. This is important because the ability to put interchange circles at a distance offers great flexibility in the overall geometry of the map.
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London 1927 (detail around Charing Cross)
Map by Fred Stingemore. Very similar to Gill's map, but physically smaller.
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London 1933, January (detail around Charing Cross)
Harry Beck's map was revolutionary, but the interchange symbol and interchange definition are almost identical. In this issue, Beck changed the open circle to an open diamond (which, when the line is diagonal, looks like a square).
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London 1933, c. August (detail around Charing Cross)
Beck soon changed the interchange symbol back to the circle used by Gill and Stingemore.
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London 1938 (detail around Charing Cross)
In a strange administrative blunder, the design of the Tube Map was handed over to the graphic designer Hans Schleger (pseudonym 'Zero') from 1938 to 1940. Schleger reduced the interchange complexes to single open circles. He also demoted all underground-to-overground interchange stations to non-interchanges. Despite his eminence in art, Schleger's dabbling in cartography was generally unsatisfactory. Witness, for example, the ugly difference between the thickness of the lines themselves versus the circles that denote the interchanges. Also, check out the very ad hoc technique of running the Bakerloo and Northern lines in parallel out of Waterloo, in the bottom right-hand corner of this excerpt.
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London 1940 (detail around Charing Cross)
In one edition, Schleger added mainline termini as blue triangles. This adumbrates Garbutt's move of 1970, where he introduces the intercity symbol alongside stations. what is significant is the concept of providing information by combining two independent symbols rather than using one single station symbol.
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London 1941 (detail around Charing Cross)
A fundamental design problem that had bothered designers of the Tube map ever since colour coding was introduced in 1908, was: what colour should the interchange symbol be? If A red line interchanges with a black line, should the interchange symbol be red or blue? In 1941, Beck experimented with large interlocking circles to indicate the binding between interchange stations. According to Ken Garland, Beck was pressured into trying the interlocking symbols against his better judgement.
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London 1943 (detail around Charing Cross)
In the next issue of the pocket map (skipping 1942), Beck formulates the brilliant solution of small, line-coloured circles. This persisted for almost two decades, until 1960. Note, however, that there is no white bridge connecting the interchange circles.
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London 1949 (detail around Charing Cross)
Beck rediscovers Gill's white bridge as a means of binding interchange symbols.
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London 1959 (detail around Charing Cross)
Beck widens the white bridge, making it easier to read.
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London 1960 (detail around Charing Cross)
Harold Hutchison pushed Beck from his position as steward of the Tube Map, and published his own peculiar design instead. Hutchison's design, though generally criticised, did make usefuly contributions to the interchange. Beck's line-coloured circles are replaced by black circles (a rediscovery of the style of 1920s Berlin). This is undoubtedly the most logical solution to the conundrum. Hutchison also reintroduced the mainline interchanges that Schleger had swept away, now as open squares.
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London 1960 (detail around Charing Cross)
A few months later, Charing Cross changes ftom circle to square, underlying the ambiguity of the symbol.
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London 1964 (detail around Charing Cross)
Paul Garbutt changed the squares into open circles with dots in the middle.
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London 1970 (detail around Charing Cross)
Important change: Garbutt uses separable symbols (white circle and red intercity sign) for underground and mainline interchange stations. This allows four permutations.
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London 1975 (detail around Heathrow)
Garbutt extends the concept of the interchange with an aeroplane symbol.
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London 1977 (detail around Charing Cross)
Garbutt adds variant to the mainline interchange: intercity symbol in a box, indicating that it is within walking distance.
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London 2000 (detail around Charing Cross)
Introduction of the boat interchange.
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London 2001 (detail around Wimbledon)
Introduction of the tram interchange.
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London 2001 (detail around Charing Cross)
Modification of the walking-distance interchange: now says how many metres.
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2. General evolution of the interchange abroad
Berlin 1927 (detail around Zoological Garden)
Use of black circles, adumbrating Hutchison's 1960 London map.
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Berlin 1962 (detail around Zoological Garden)
Use of open squares for interchanges, open circles for non-interchanges.
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Berlin 1967 (detail around Zoological Garden)
See-through interchange symbols.
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Berlin 2000 (detail around Zoological Garden)
The standard European white blob interchange symbol.
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New York 1944 (detail around Times Square)
The lassoo interchange symbol. Early map by the Board of Transportation, later to become the NY City Transport Authority. The early maps issued by the Board of Trasportation were actually drawn by Andrew Hagstrom's company.
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New York 2000 (detail around Times Square)
Standard NYCTA map. Black lines of varying sizes between interchange stations. Ugh.
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Japan 1929
Intercity electric railway. No special symbol for interchanges.
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Tokyo 1971 (TRTA)
Evidently inspired by London maps. Compare with Beck post-1949.
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Tokyo 1996 (TRTA)
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Tokyo 1996 (TRTA)
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Tokyo 1995 (TOEI)
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Tokyo c. 2000 (TOEI)
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Tokyo 2000 (TOEI)
Three-dimensional interchange symbols.
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Tokyo 2000 (TOEI)
Detail of three-dimensional interchange symbols.
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Seoul 2000
Purely decorative interchange symbols.
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3. Specific evolution of the interchange at Paddington
London 1918 (Paddington)
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London 1921 (Paddington)
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London 1933 (Paddington)
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London 1938 (Paddington)
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London 1941 (Paddington)
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London 1949 (Paddington)
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London 1960 (Paddington)
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London 1964 (Paddington)
Three circles, not fully connected.
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London 1985 (Paddington)
Hammersmith & City Paddington is expelled!
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London 1989 (Paddington)
The best symbolisation for Paddington: three interconnected circles.
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London 1997 (Paddington)
Hammersmith & City Paddington is demoted to mainline interchange only!
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London 2000 (Paddington)
Back to three bridged circles, but now more symmetrical than in 1989.
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London 2001 (Paddington)
Hammersmith & City Paddington is isolated but is now an open circle.
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See also: interchanges table.