Friday, 25 April 2008

Driver location signs – information or noise?

Driving regularly on the M4 and M25, I started noticing new signs, which I couldn’t immediately understand. They turn out to be driver location signs, and seem to be unique in not being part of the Department of Transport signing system – they are in fact put up by the Highways Agency, the body that repairs and provides emergency services on UK motorways.

What was it that puzzled me about the signs? There seems to be an ambiguity about them – are we supposed to see them, and understand them, or are they really intended for highway engineers? I tried to work out why they seemed ambiguous to me. They share the graphic language (colours, typefaces, configuration, media) of motorway directional and warning signs, but these design elements have been tweaked to make them just a little less clear. Orange letters on a blue ground do not have the obvious contrast of white on blue, and the lines are centred. The coded form of language used (‘M25 | B | 43.8’) also sets them apart from the straightforward use of placenames or pictograms on other motorway signs. They are really quite large, and certainly frequent – they occur every half-kilometre or so, but the Agency seems happy to place them beside other roadside objects, or just behind other signs, in a way that would not be acceptable for warning and direction signs. So they look like an add-on to the system.

All of this brought to mind thoughts of how unnecessary elements, especially pattern elements, can distract the reader from information content. It seemed to me that every other motorway sign is encountered only when the motorist actually needs to know the information – on the approach to a junction, or a hazard. These signs really look like signs (because they share the features listed above with true signs) but I think they are really more like the labels on grid-lines or chart axes: they orient, rather than give new data. My first guess was that they were replacements for the much more modest kilometre posts (actually every 100 metres along motorways), and this is pretty much the case: DLSs are intended to give drivers location information that they can relay to the emergency services by mobile phone. The size is dictated by the need to be legible from a moving vehicle in the fast lane – meaning that they have to be as prominent as other signs.

So, do they constitute necessary information or are they the motorway equivalent of ‘chart junk’? And another question is thrown up by a note on the Highways Agency web-page on DLSs:

‘Promoting and communicating the function of the signs is central to them being successful. The public need to be fully aware of the three pieces of information on them so they can then communicate accurate locations to control rooms. The current strategy to disseminate this information will be done through a national press launch which will publicise the purpose of the signs. This will be further supported by local press notices through regional media.

‘Aside from using external communication methods the Highways Agency will also be distributing leaflets and information cards on driver location signs to drivers within areas of installed signage. They also plan to display pop-up posters in prominent locations frequented by drivers.’

So, did you know about them and what they mean? If you see a pop-up poster (whatever that is) do tell me!

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