TT Scale. The Ideal Scale.

I'm going to second what 'sailor said. You should put in one or two trunouts that go nowhere (put some overgrown grass, etc. on them) so you have options for expansion later. If you don't expand, no biggie - but you have the option.

Here is the photo of the 4'x8' layout that I bought before it had to be taken apart due to the plywood being water damaged.
With the curved track that was used, it would not be very hard to have a 3 foot wide module with the U shaped arc leading to and from other modules and have a small city scape with a railbus or trolley car, or something like that.

Thnaks for the photo, AngrySailor!
The radii on those ovals are way too tight for may liking, but I am going to explore the possibility of a folded dogbone a little more.
Wih respect to spurs lat lead nowhere, That's a great idea, and pretty much all my spurs can be extended to other modules, if needed. The issue is that making them perpendicular to the module edge (for easy connections) make the use of space on the module less than optimal. I'll see if I can work out an acceptabel compromise!

An idea for the spurs that go nowhere:

Build a mountain at the end of the layout, and have the spur going into a tunnel.

Just make sure that there is a buffer or something at the end of the track to prevent someone from inadvertantly sending a train off the table via the "dead end" spur!