Recently, I came across this rather fine little trolley layout.  Unfortunately, there are no sizes or track plan given.  The plan is pretty obvious, though I’m not sure what happens around the back of the layout.  As for size, it’s probably 4′ long – though one could get a good estimate from those DPM buildings.

It’s a pretty generic trolley layout, but if you wanted to run almost anything, mainly for fun, its an attractive little design.