Bet you've never noticed this about the Tube map
Why do some lines go over and some go under?
Much celebration today at the unveiling of a blue plaque to Harry Beck, inventor of the cultural icon and design classic that is the London Tube map. You don't need me to tell you about his genius insight that the map didn't have to be geographically accurate: that's in all today's news reports. (If you want to see a pre-Beck map, there's a fantastic original in a glass case outside Temple station.) Instead let me share my favourite little quirk about the map as it appears today.
There are two sorts of Tube line: ‘cut and cover' (the early ones, like the Metropolitan and District, built by digging up the road, putting down the tracks then relaying the road), and ‘deep level' (made by tunnelling much further underground, for instance the Piccadilly, Northern and Central lines).
Take a look at the Tube map: whenever a cut and cover line crosses a deep level one, it goes over rather than under it, to mimic what happens in reality. In the 1980s London Underground accidentally printed a version of the map where a deep level went over a cut and cover. Beautiful pedants that Londoners are, several wrote to point out the mistake. A new version of the map was duly issued.
Now that's what you call attention to detail. I bet old Harry Beck is smiling down in approval.