Frankfurt - Mannheim - Karlsruhe, Hamburg - Hannover, Berlin - Liepzig lines are some of the ones I can remember. High speed was mostly 160 - 200 KMPH. I used to create 18 coacher user trains with DB 101, my favourite loco, and it used to perform really well. Could reach 160 KMPH in 1 min or so. I personally don't like high speed trains in the game as they dont have a good pickup and breaking is also not immediate.