Under the twelve-percent-grade limit, those track segments go flat-to-12%, 12%-to-25%, 25%-to-12%, 12% straight, 12%-to-flat. Those new track pieces are awesome, but the planner doesn't seem to know how to use them legally.
This seems inappropriate, since the middle of that vertical S-curve is indeed a forbidden 25% grade- and the average across those two pieces is about 17% (1 rise over 6 run, versus the 1:4 of 25% and 1:8 of 12%). Though it is nice that this probably means you can start building from the end of a 25% while the 12% restriction is active, and it'll actually let you build.
Update 4.2 | v0.8.6c (b612)
Reproduction:
- Start the track building planner, with 12% grade restriction active.
- Minimum height change of 3 if starting from flat, 2 if starting from a 12% grade.
- I was using the straight-only modifier, this is not necessary. What is necessary is to position the cursor too close to the starting point for it to find a valid solution on only straight 12% sections, but far enough for it to use 17% sections.
- If the grade change (and planning distance) is large enough, it'll use multiple 17% sections.
I was not able to convince my game to do this with curved grade-transition pieces as well, but I'm also not certain that those exist, and was testing on flat terrain (might not be enough grade change available).