Train station musings

At the moment I am on the rail platform awaiting a train. I'm at Woking which is half way between my house and London. The thought that occured to me is : if it's only half the distance to London why is the fare less than 40% of the fare to London? Surely it should be half the fare? Or is that too sensible? It makes no sense- but neither does the fact that there are two girls sitting opposite me who are having a text conversation with each other . . . (Post sent from my mobile phone)