Where my German friend comes from (Hemsbach in Baden-Wuerttemberg on the edge of the Odenwald), they have a very very simple system - the whole train system is broken up into hexagons, like a beehive. If you want to travel from one place to another, you just count the number of hexagons through which you'll pass and pay per hexagon. If you decide en-route that you would like to go further, you can buy extra hexagons on the train from the ticket collector, or when you get off.