Legibility, Functionality and Organisation

It has been a while since I have written a post relating the London Underground diagram (LUD) and information design. This week a good friend of mine send me a link about a new layout for the LUD proposed by a UK design studio. Later this week I found an article in Metro while going to work about it which made me decide to give this LUD a proper look. This post discusses an analysis of this new proposed layout of the LUD from an information design perspective.

The redesign of the LUD doesn’t seem to be an easy task, as this is not the first attempt to improve the original Beck’s design. Three are the key factors that make the LUD an iconic piece of information design that should be taking into account when developing a new version: Legibility, Functionality, and Organisation.

Legibility. The legibility and understanding of the LUD has been deeply analysed by Max Roberts. In his last exhibition, Underground Maps Unravelled (2010), he presented his research work about breaking initial Beck’s design rules in order to obtain greater understanding. Roberts (2005) explains that the difference between Beck’s and other LUDs is that Beck defined and strictly followed a set of fundamental design rules to produce a usable and effective piece of design. Beck’s design rules are summarised as follows:

– Use of only horizontal, vertical and 45-degree lines
– Enlargement, reduction and/or distortion of accurate areas in favour of comprehension
– Use of graphic codes
– Elimination of useless details
– Main components well distinguished
– Use of colour codes
– Information architecture (conceptual and visual structures, see below)

By a systematic alteration of some of those rules, Roberts developed a series of LUDs exploring different degrees of legibility. One of his conclusions is that the effectiveness of an underground diagram is related to legibility and understanding. And these qualities can be measured according to the number of ‘elbows’ composing a network (of  tube lines, in the case if the LUD). An ‘elbow’ in this context refers to the change of direction in a line and the number of breaks produced in a straight line, which both have a direct effect in how the trajectory of a line is perceived. The trajectory of a line is understood by connecting the initial and ending points of a line.  In other words, the more elbows a (tube) line has, the more broken it is perceived, and the more time to be understood is required.

This image presents a sequence of lines, which starting point is a straight line with no elbows and the last one is a highly broken line. In the first line both the initial and ending points of the line can be easily connected, which means that it has a high level of legibility. The following lines are broken as they include an increasing number of elbows, making more difficult to visually connect initial and ending points. In the last line the relationship elbow-legibility can be fully appreciated.

In previous studies about the LUD, Robert has experimented to increase and decrease the number of breaks in a line, and to modify the angle of the lines to evaluate the different levels of legibility. Results have shown that often the more line intersections and breaks a LUD has, the more cluttered and highly confusing its layout is perceived.

Funcitionality. The main goal of the LUD is to visualise the London underground network, underground stations, and interchanges between underground lines to orientate commuters in the navigation of London city.  The current LUD (as well as its very first version) was never aimed to be a pocket ‘street-guide’ for Londoners or tourists, which could replace the A-Z map. Garland (1969, 1994), Walker (1979) and Roberts (2005) have widely discussed this concern about the LUD, concluding that sometimes the LUD is being misused and ‘being asked’ for more than it has been designed for.

Organisation. The organisation of a (complex) diagram, as the LUD, is based on its information architecture. The information architecture refers to the internal and external structure followed to organise the elements of a diagram. Costa and Moles (1992) explain that as information presented in diagrams is a synthesis of the whole message, it should be organised in types of information first. Those types of information constitute the skeleton of the internal organisation of a diagram. This is the conceptual structure. The external structure refers to the rationale to visually organise those types of information, which will determine the visual structure of the diagram. The way those types of information are interconnected depends on external factors, such as purpose and goal of the diagram and audience, among others. The current LUD is based on a 7-layered conceptual structure, including (1) Navigation: Grid, border, ground, (2) (Geographic) reference, (3) Main structure: Network, (4) Main components: Interchanges, (5) Colour and visual coding, (6) Textual information, and (7) Additional information. And its visual structure is based on the above rules 1 and 2, resulting in a highly rigid grid.

It is dufficult to analyse conceptual structures of diagrams, as this would require deep analysis, however the visual structure is easier to explore. Often new version fo the LUD are based on modifying the angle of the lines (see first Beck’s rule  above). Attention should be given to this point as when these angles are changed, the whole structure, and thus perception, could also change.  As an example, the use of 30 and 60 degrees only to visualise the underground lines, instead of 45º, can be perceived as a weak or lack of structure in terms of the whole network, which may difficult its understanding and legibility (see above: Legibility). In addition, it also may be perceived as a messy bunch of elements without a grid system behind.

It’s true that when Beck created the first version of the LUD there were fewer tube lines (and no Overground lines) than there are now. However, this should not be a factor to invalidate Beck’s work, as his design principles have already demonstrated to be well defined at the point that the basis of the LUD has not been changed since its creation in the 30s. In other words, the LUD has been adapted to the growing underground network over the years. For sure, it would be great achievement to design a new version of the LUD as effective as the original one, but for that, any further attempts of redesigning the LUD should be based on improving (or at least considering) the three factors briefly discussed in this post, that also constitute the basis of information design.

– Costa, J. & Moles, A., 1992. Imagen didáctica. 2^nd ed.Barcelona: Ed. CEAC.
– Garland, K., 1969. The design of the London Underground diagram. The Penrose Annual, 62, pp.68-82.
– Garland, K., 1994. Mr Beck’s underground map: [a history]. Harrow Weald: Capital Transport.
– Pontis, S., 2010. De intuición a teoría. Caso de estudio: el mapa diagramático del metro de Londres. Quadra. Revista de diseño y comunicación visual, 5, pp.25-34. Mexico: Universidad de Guadalajara.
– Roberts, M.J., 2005. Underground maps after Beck: the story of the London Underground map in the hands of Henry Beck’s successors. London: Capital Transport.
– Walker, J.A., 1979. The London Underground diagram. Icographic, 14/15, pp.2-4.

– Information contained in this post is also based in results obtained from the Case Study Analysis (2008-2009) about the LUD  conducted as part of my PhD thesis.