Visualization lessons from the roadside

At the weekend I read a fascinating newspaper article, unlikely as it may sound, about road signs. (I should stress here, comrades, that the Telegraph in question was bought by my otherwise sensible father-in-law.) It is now online too. The reason it held me transfixed in my armchair on a rainy Sunday morning was the many parallels with data visualization. Although I’d never given much thought to them, of course every aspect of these signs were designed and chosen carefully. The primary objective is safety, and so the information has to be absorbed rapidly as you whizz down some quaint English country lane. You know, like this:

A screen shot from the
A screen shot from the Yorkshire edition of Grand Theft Auto

As we are often told of how alarmingly little time we have to get a reader’s attention before they move on, some of these ideas are worth considering.

Firstly, the typeface is chosen for its simplicity, and directing arrows stylized. Where we used to have more accurate depictions like this:

Good luck, drivers! (c) maljoe at flickr
Good luck, drivers! (c) maljoe at flickr

We would now simplify that a lot, especially that it is actually just a T-junction, but you can only work that out once you have absorbed all the information in the sign. So, taking Gelman and Unwin’s advice to always present in more than one format, it might be worth having a simplified depiction of your key message up front, and readers then click through to the detail, to the level that they want.

A limited palette of colors and icons is a good thing too. The road signs went for contrast but usually in data viz you want a limited spectrum, shades of blue for example, with the odd splat of orange picking out some detail. And lots of blank space! Don’t feel the urge to clutter it up. The schoolkids crossing the road used to look like this:

Happy days (c) jp4712 at flickr
Happy days (c) jp4712 at flickr

Again, reality had to be subsumed to clarity. That’s why I feel anxious about the constant reference to data visualization nowadays. A lot of the time, you don’t want to show people all the data. It’s just too much. That’s why we have stats!

Jock Kinnear and Margaret Calvert, whose signs first appeared in 1958 and went national in 1963, also took pains to find out whether mixed upper- and lower-case type would be more quickly absorbed than the old upper-case (consider BIRMINGHAM or Birmingham). Excellent, evidence-based work.


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