The semiotics of street numbers

Around the world people have come up with different ways to organise the numbering of buildings. Growing up in Australia I assumed it was logical that you would use a numbering system where the numbering started at one end of the street and had even numbers on one side and odd numbers on the other side. That way, if you needed to find number 22, you would know which side of the street to walk along and which direction to walk in (once you could work out which end of the street you were at).

In Uganda, we didn't have the chance to test out very many neighbourhoods so I'm not sure what the system was. Generally they use ‘plot' numbers, but I'm not sure if these were arranged in numerical order or not. Google maps doesn't tend to show plot numbers and only some of the addresses Google shows for businesses on the map include the plot number.

When I went on exchange to Japan many years ago, the street address had something like 5-33-1 and then the area name, and I never worked out what the numbers meant. This Wikipedia page gives some explanation, but I'm still confused! Apparently most Japanese streets don't have names; rather, building numbers are worked out by blocks.

Here in Florence (and this may or may not be the same for Italy in general), I thought the system was the same as in Australia. There are building numbers shown clearly by means of a number tile attached to the wall of the building, and they increase in twos, with odd and even numbers on opposite sides of the street. But I sometimes saw in addresses something like '52R', and wondered what the 'R' meant. I learnt that it stands for rosso, meaning 'red'.

Someone explained to us that at some point in time, some of the larger buildings were divided up and different entrances were added as more apartments were created, or a large building that had a garage at street level sold the garage to someone so that it needed to become a separate address. The new entrances were then numbered with red number tiles arranged sequentially according to the red numbers in that street. (In Australia we would use the letters a, b, c, etc to indicate new subdivisions at the same street number.)

The original numbering system uses blue number tiles and is numbered in the same way as the Australian system. So now what you see is two different numbering systems side by side in the one street. Often the numbers appear out of order, as in the picture below (59, 65R, 61), but once you know the difference between the red and blue numbers, it makes sense.

Since learning this, the semiotics of the number tiles have become clearer. I had thought that the differences between number tiles was due to the style preferences of the building owner. In Australia, whoever owns or designs the building chooses how they want to indicate the number (or not). Now I could see that the blue number tiles are basically the same throughout the city (with some minor differences) - they are larger and have a glossy glaze. The red number tiles are usually smaller, with a matt finish and the number in recess (although occasionally they are red versions of the blue tiles, in the picture at the top). I also noticed that the tiles tend to be placed at a reasonably consistent level on the wall, with blue number tiles relatively higher and red number tiles relatively lower (unfortunately, neither of the pictures here shows this tendency!).

So there are different semiotic systems for identifying buildings - numbers, colour, letters, number placement - and perhaps none is particularly more or less logical than the others (although the Ugandan one is still a bit of a mystery!).