I wish I could do the London tube but it’s cyclic. Even for Amsterdam, route 50 was a bit of a kludge as you’ll see in the tree.<p>Here’s an image with tag/branch names for the lines: <a href="http://i.imgur.com/vXhLYry.png" rel="nofollow">http://i.imgur.com/vXhLYry.png</a>