Black Flags have a bad connotation in most situations, but in road racing, they can mean many things.
A black flag is shown to a specific driver by a track worker. Generally, the flag is waved as the driver approaches the flag station, and is then furled and pointed directly at the vehicle so there’s no mistaking who it’s for.
It’s a bad feeling to get black flagged.
When you see that signal, you are supposed to head for the pits, because the grid marshal or their representative wants to talk to you. It could be anything. It could be that your car is leaking something that it should not be, and that flag just saved your engine. It could be that you’re driving too close to the edge, or that you just spun the car and they need you to pull in to inspect it.
I managed to forget my instructor once. It was just before I was signed off solo and I was sitting in the starting grid, waiting to go out on track. When the grid marshal looked my way, I gave him the thumbs up, and he waved my on track, solo. I went around a couple times, and got black flagged. I pulled into the pits, and there stood my instructor and the grid marshal.
“Missing something?” says he.
“Yeah! The car is handling different, like it’s a couple hundred lighter or something…” I say.
“Uh huh. Well, don’t do that again.” He’s serious now.
“Nosir”.
“Go on back out”.
My instructor gives me the eye as I shift.
“You think I weigh 200 pounds?” he says into the intercom. He’s around 5’9″ and nowhere near 200 pounds.
“Well, a svelte 200, maybe 190?” I’m accelerating out of the pits.
“Shit”. he says.
Then again, you can get black flagged for hitting another car, driving too aggressively or simply being too sloppy. It’s not generally a laughing matter, but I’ve never talked to anyone else that forgot their instructor.