Black flags appear when you cut corners or do a short cut. A black flag will appear in the left corner of your screen for 10 seconds during which your speed will be capped so u cant go above a certain speed. After the 10 seconds your speed will go back to usual.
I agree with all that disapprove black flags in certain places (eg. monza first chicane); infact, using track editor, i simply remove black flag commands from sector and no penalty will applicate when cut the chicane); is not user friendly but is better than nothing.
How does the game calculate the black flags anyway? Is it speed related? For example if you enter a black flag zone over the specified limit you get a black flag.
I was driving in Melbourne and i went up a curb whilst accelerating and got a black flag i did not even touch the grass it was just my 2 right wheels on it.
And yet in imola u can totaly miss the last corner by going str8 down the old road and not get a black flag, yet cut the last corner and get one strange