lol I came upon a BMW that clearly had just missed his turn (he slowed down, realized it was too late to make the turn, then sped up again), then turned on his turn signal to pull into someone's driveway to turn around.
I said to my wife, "This BMW driver is so lost, they're using their turn signal!"
I think it means your speedometer is displaying double your actual speed. So you can go at a speed that the speedometer says is twice the speed limit, and you'll actually be going at the speed limit.
Shit man, you gotta get that checked out. This is the "honk at me" feature. It means your car has detected that you're an idiot and everyone will start honking at you and passing you on the right.
Do you also hear a ticking sound? If so, the car just entered a SUICIDE BOMBING MODE. It's on a timer to let you escape; follow the arrow for the nearest exit.