FreeGameDev

my idea is, that you have a percentage summary of "on pipe" in a track percentage summary of "on pipe" of a track, for tracks like pipeline or my new one dangerroad or radioactive
(like "in air" and "pipes")

Is quite difficult to implement. I would have to use the track's ghost and run it to check if you drive on pipe.
Editor doesn't know if you will drive on or in pipe. (track's ghost is used in game, made by me and that's even more complicated).
Would be cool thought to have it, yeah.

Hm. We could mark segments as on-pipe. Then it would be easy to do.
Is just another key in editor and more clutter in road point tool window and also a place it on track tab (near the pipe % right).

what is, when you drive on the pipe and in it too???

Already implemented. ctrl-9 marks road segment in editor as "On Pipe".
Good call. When you drive both on and in pipe it's ok: because the on-pipe sum is right when segment is marked (so you mark it as on pipe) and the rest stays same, pipe % gets computed as usual, basing in pipe fraction.
Only difference may happen when you drive on pipe eg. somewhat shorter than the whole road segments marked as on pipe. But then it's not a big difference and I always recommend using more road points (not to few).