Flash hazard lights to say "thank you"

[jack]

For a while, I've noticed cars flashing both indicators simultaneously (presumably by turning hazard lights on then off again) to say "thank you" for letting them in.

I think I first noticed it by lorries -- google suggests it may have been a lorry driver custom first.

I really like the idea of being able to say "thank you" or "sorry" as well as "please" or "get out of my way" when driving.

Am I right that it's new, or did I just not notice when I started driving?

Presumably it's not allowed (just like flashing headlights to say "excuse me" or "after you" or "do you know your lights are on/there's something wrong with your car/etc" was never an authorised use according to the highway code). Is it a bad idea, or not?

Comments

[eudoxiafriday.wordpress.com]

I've not done it myself, but I've certainly noticed it. I think it's really nice to have a way to say thank you to someone behind you, in particular (e.g. for slowing down to let you in). I think I've seen it mostly (only?) on motorways.