Polite light flashes

[mtbc]

On returning to driving in the UK I have noticed an unofficial pattern of behavior that is new to me. A persistent issue for drivers of large trucks is that overtaking car drivers pull back in too close to them so they do not have much clear road to stop in if necessary. So, when I have passed some distance ahead, the truck flashes its lights, then I move back into their lane, then with both my turn signals I give a quick thank-you flash, learned from observing others. It is a simple but pleasing exchange.