Lionel Fastrack with O-36 minimum. The design goal is a track plan for multiple train routes with multiple trains and layout automation fun. This plan will support many three and four train operating patterns that can run under layout automation. There is also a small yard, and five industry spurs, and a number of buildings.
The simplest operation is two trains on the outside route in the same direction, and two trains on the inside ovals, for four trains total, not requiring layout operation.
The middle horizontal connecting line has two O-72 "Y" tracks making two Wyes, allowing trains to reverse direction and make the connection between the inside ovals and the outside route. The inside ovals also have their own connection at the top of the plan, making a third horizontal oval that overlaps with the two inside ovals (and also overlaps with the outside route), with the possibility of FIVE trains running at the same time!: three trains on the inside ovals, and two trains on the outside route. Pretty tricky timing to make this work, and requiring some turnouts to be thrown automatically.
Even more interesting and challenging would be routing 3, 4 or 5 trains making a "Grand Tour" using the wyes to route over the entire layout, under layout automation control!
A project commissioned by a forum member. -Ken