So... you're interested in creating the longest possible ride path at the slowest possible speed. Ok.

Well first of all I should point out that the OC does not result in the longest possible ride time, for one simple reason... it's all only on one level.

In RCT, you can stack ride track on top of other ride track, so long as it doesn't interfere with it. Usually all that means is that the next level of track has to be 2 height units above the first. So, what really matters is not using up all of the available park space in the largest possible park, but rather using all of the possible build volume. See where I'm going with this?

So here is what you need to do to get the longest possible ride time.
- Create a park of the max possible size (as in the OC)
- Raise the land height to the max possible level (so that you can also build underground)
- Have a spiraling path layout, as in the OC, but have the termination point at an edge (not exactly sure how to do with with a rollercoaster because the minimum turning radius is 2 tiles, so you might have to redesign the path)
- Use a roller coaster that let's you build to the greatest height (Gigacoaster)
- For each new level, do what the OC does, chain up to the next level, then break down to the minimum speed.

It's been a while since I played, and I don't have the game installed, but I *think* you could do something like 80 layers of the OC in one ride, which would take about 16,000 real life days to finish, which would be about most of the rest of the life of the player, or about 384,000 in-game years. Of course the game might not even accept such a model (might crash), nor would it be possible to construct without some kind of script.

Oh, and the ride speed does not asymptotically approach zero. It reaches a minimum threshold of about 1mph to "avoid problems".