Raised Platform Railroad
I'm building my current railroad like a series of decks, from 24"-65" in height. My yard drops 6" every 10', and my back is not what it used to be, so this is a way to keep everything level (even though each loop is a foot further from the ground at the far side of the railroad than it is at the near side).
In part, I'm building it as a sort of "proof of concept," because so many of my friends who got into the hobby the same time I did have had to abandon their ground-level or near-ground-level railroads entirely. In many cases it was heartbreaking for them. Now I only recommend ground-level railroads for temporary installations while you're planning a permanent railroad.
I used to recommend attaching your roadbed right to posts, then backfilling with dirt. But several friends who have done that (most of whom, I admit, took shortcuts I recommend against) have had roller-coaster or other track movement issues. Not to mention that in places like Ohio, all that extra dirt gives weeds a lot more opportunity than a solution that puts dirt only where you actually need it.
Also if you want to change your track plan later, you have to dig more holes. With a raised platform, you can make adjustments or even add turnouts, yards, and other features you didn't have at first.
Since I started publishing about this, I've come across a lot of other outdoor railroaders who have done essentially the same thing on at least part of their railroad, but they've kept quiet about it because folks have complained they're not "doing it right" or some such.
Personally, I think the hobby will keep growing best if we can keep showing families ways they can install a low-maintenance railroad that will serve them, if necessary, decades into the future without periodic massive refurbishment.
Hope that makes sense.
Best of luck!