As a Texan, it pains me to say this, but the most polite drivers that I've encountered were in Ohio. I lived there for a few years and found that it was common for people to give a thank you wave when you let them in. It's more rare here down south.
The Japan Channel, a YouTube channel about life in Japan, reports that Japanese drivers do something similar. If you let one in, s/he will signal thanks. But Japanese drivers do this by briefly flashing their hazard lights.
That's a pretty good idea, especially since it could be seen at night. What do you think? Should drivers in other countries adopt this practice?
-via 22 Words