But!  That doesn’t mean that 256sq km is a bad map size!  In fact, it could be great! Here’s an idea: cargo/passenger loads coming in from, or demanded by, the edge of the map.

It could work in such a way that tracks could be drawn off the edge of the map, and that ‘endpoint’ added to the train’s orders.  This would allow us to simulate long-distance travel in and out of the area we’re playing.  It’d be great for giving us the feeling as playing as a part of a larger world!

Just something to think about.

as an example, Virtual City (a little transportation game for iPhone and iPad) uses this kind of thing. There is an arrow on the street that reaches an end of the map and that arrow works exactly as a bus stop/cargo depot, with passengers going in and out or by accepting goods in order to produce other goods.