The modular railroad clubs all have variations on 3x6 or so sized panels to put together for a large layout (often layouts are longer than 100' which can make for the running of long trains). Go search the web for those groups and you will see a number of variations of how to do a module type railroad.
-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!