Bob, to be more accurate I should call these "compromise easements" because I'm using sectional track pieces with different fixed curve radii. But it gives a substantial improvement over joining a minimum radius curve directly to straight track.
I'm not personally familiar with Atlas O track but I see that they have a good selection of different curve radii. Any wider radius curve between straight track and a tight radius curve will give some easement effect. On my larger O-gauge layout I use O72 easements for O54 curves; in other words, I don't join the O54 curves directly to straight track. And it doesn't widen the overall diameter of a curve very much. The easement section only needs to be about a carlength long to be effective, usually just one section of track.
If you want to try this with a different brand of track, the best thing is to experiment to find what looks good with a train running through it. It may be a trick to minimize cutting of pieces to fit, depending on the track plan you are trying to build. The plan that I built, shown above, didn't require any cutting.
In HO I did easements mostly by eye with flextrack, just so they made smoothly flowing curves that looked good. With N gauge I sometimes used sections of 19" radius as "compromise easements" for 9.75" and 11" radius sectional track.
Following is an example of simple ovals with easements using O-gauge sectional track, and the fixed radii juggled to make reasonably concentric curves.
