Atlas and Lionel. If I had more Atlas track I could complete it without the Lionel, but that's OK. Notice each lane uses each radius, hence the need for 12 crossovers. The rotation is 1,3,4,2 working from lane 1 (inside) to lane 4 (outside). I needed to add the precious 3-inch lane segments to make the track wide enough. Of course, I may change it to 12/15 curves instead of 9/12 but I just had to see how much space I need on the plywood to accommodate both layouts. Also, notice that I have 6 of the necessary 8 pieces of Atlas single lane track - luckily, with how atlas/lionel joins, you can simply offset a two lane track piece to create a one lane length as long you are have space on the outside.
So many ideas with this track.
Edit - The original Atlas layout does indeed use 12/15 on diagonally opposite corners and 9/12 on the other two. Again - you can do anything you want to change it up. Everyone has to ride each corner radius no matter what you decide!
