American Flyer radius is 20 inches, what is the radius of Lionel 3 rail? that is what needs to be compared, not Lionel 3 rail to S scale. How about Lionel 3 rail to O scale. Do they all operate on the same radius? it's not the radius as much as the design of the model. this argument has been around forever and it all depends on how eyes are looking at it. American Flyer fans wit tell you they have real scale trains. Yeah, they have two rail AC power and the Lionel has 3 rail AC power.