I was going to write about this, but someone beat me to it: London Underground Tube Diary - Going Underground's Blog. There is a new ad campaign from Flora "Could you walk it quicker?" which suggests people should walk between locations that are close together for their heart. Of course, it would also relieve transit congestion, if taken up, as many stations are really quite close, especially after you consider the underground access costs, the closeness is shown on the maps