A little quiz for the readers: I am on a train in a major European city and this is the pattern on the PVC in the carriage. Now where am I? 
A clue: Look for big important buildings you might know.
The Brandenburg Gate. The Reichstag. The TV Tower and now we are getting more into things for the locals, The Red Town Hall ; the Deutsche Dom etc.
Yes, that's right. I was in Berlin (again).
When I realised this, I thought how great. Let's use the semiotically most important symbols of our city to decorate the way you get around them.
I know that the Tube has a different pattern for the seat covers for different lines as witnessed by another quiz here but that's making it too difficult for tourists.
Imagine fitting the symbols to the places the line goes under or even to. You could have Buckingham Palace on the Piccadilly Line and the Victoria Line because they both go to Green Park and it would be a much nicer of way of working out the intersections.