This was my Artin 4 lane road course:
I overlapped 2 sheets of 4x8 plywood, but it would be easy to extend if you had room to put them in the L shape without overlapping. There was one custom straight that I made by shortening an existing straight (you can kind of see it in the bottom right of the picture).
Great track, loved it. Finally let it go this year when I routed my first wood track.