WHY?
In my job, we sometimes need to present data about postcodes, and a map is a very visual way of doing this. I often wanted a postcode map that I could use in presentations, but one where the individual elements could easily be colour coded. This map meets that need – it is very easy to create and modify, and while it makes compromises about geographical accuracy, it retains enough similarity to real geography to allow users to relate it to the intended locations.

HOW?
MS Excel.
But in theory you could make a map like this in many different ways, which is part of its attraction.

You could make one using many other types of computer software, including graphics/presentation packages like MS Powerpoint, word processing packages using the table functions, and database packages like MS Access.

Using spreadsheet or database packages, you could link the map elements directly to the related data, to drive colour coding, or the inclusion of other elements such as people’s names etc.
You can also easily create a map like this even if you don’t have a computer, by using graph paper or plain paper and a ruler and pencil.
You could even produce one on a typewriter, or out of toy building blocks.

And you don’t even need to have detailed knowledge of the geography of the area you’re mapping – as long as you’ve got a rough idea of the relationship between the elements.

CAN ANYWHERE BE MAPPED LIKE THIS?
I don’t see why not. In principle you could map any set of areas like this, as long as you can make acceptable compromises about geography. For the UK postcode map, the size difference between the smallest and largest areas is so extreme – many small areas in London, generally much larger elsewhere – that I had to use a separate enlarged section for London, which I think is acceptable. The USA has a similar problem – many of the mid-western and western states are roughly the same size (and roughly square too!) while there are many tiny states in the north east, but I’ve managed to get them all in without needing an enlarged section.

WHAT ARE POSTCODE AREAS?
Postcodes are assigned by the Royal Mail to every address in the UK, to help them deliver mail, and therefore form part of every address. Many commercial addresses will have their own unique postcode, while residential addresses usually share a postcode among a group of houses. A typical postcode might take the form ZZ99 9ZZ, though there are variations on this - the second part tends not to vary, but the first part can also take the form Z9, Z99, or ZZ9. The first one or two letters of the postcode are called the area code, and these are derived from the name of the local city or town, or in the case of London, from the district of London - for example, S for Sheffield, SA for Swansea, W for West London. The other parts of the postcode are allocated without reference to the name of the local town or city. As the area code is the only part of the postcode that is obviously derived from a named town (and thus can be guessed if the postcode is not known), this is what I have based this map on.

Postcodes are widely used in business, for reasons other than addressing mail. They are commonly used to decide insurance premiums, and to split sales teams into regions. My employer uses them, among other things, to help manage the physical distribution of goods, which is another very common use. There are sometimes requests to change postcodes from people who believe their postcode unfairly influences their insurance premiums or their real estate value, both of which can happen, but the Royal Mail usually rejects these requests and makes changes only when they deem it necessary for operational reasons related to mail delivery (such as new buildings making existing postcodes full). Although the postcode areas appear all the same size on my map, the Royal Mail make no attempt to have postcode areas the same size, either geographically or in terms of the number of addresses.

Wikipedia has a good section on postcodes.

ARE THERE ANY OTHER FEATURES OF THESE MAPS THAT MAKE THEM USEFUL?

Most maps attempt to achieve a high degree of geographical accuracy. But they are often used for purposes where pure geographical accuracy is not really that important. In the United States, the individual states differ enormously in population, and their populations are utterly dis-proportionate to their geographical size. Thus geographically accurate maps of voting patterns, for example, push small but highly populated states out of the picture, which becomes dominated by geographically large but often under-populated states. Maps like this one have an added value when the individual elements do actually have equal significance in some respect – in the USA an example is in the US Senate, where each state has equal representation by two senators. Here's someone else's attempt at something similar.

AREN’T THESE MAPS REMINISCENT OF THE PERIODIC TABLE OF ELEMENTS?

I thought so too, hence the map of postcode elements.

AREN’T SOME ELEMENTS NAMED AFTER REAL PLACES?
Yes they are, including Californium, Darmstadtium and Strontium.

I’VE GOT A SUGGESTION FOR IMPROVING IT / I’VE FOUND A MISTAKE!
Great ! I welcome corrections and suggestions for improvements. Send them to me at motorwaymap@yahoo.co.uk. If I agree with you, I’ll change the map for future versions (though maybe not soon).

CAN I BUY PRINTS OF THESE MAPS FROM YOU?
I don't currently have facilities to do this. If enough people are interested in this, that may change. Let me know if you're interested in this - mail me at motorwaymap@yahoo.co.uk