My ex-brother-in-law got hit by a motorcyclist. His left blinker was out on his truck so he signaled by sticking his left arm out the window. The motorcyclist took advantage of the truck slowing down in front of him and went to pass on the left only to be taken out by the truck turning. Because in this day and age, regardless of if it is taught or not, no one signals with their arm in a car.