You are driving on the highway and overtaking a large truck. As soon as you pass it, you suddenly see a brief flash of light in your mirror . You might immediately think the driver is angry. Or that you are driving too slowly and need to move to the right quickly. However, such a brief light signal after overtaking usually means something completely different. Often, the truck driver is actually trying to help you.
Truck drivers use various informal signals on the road. They can send each other short messages
