Flashing your lights just says "pay attention to me and try to guess my intentions" - it can mean that the driver is giving way poltely, and more often than not that is the meaning in Elgland anyway; but sometimes it means "I'm coming through, get out of the way".

And remember in the UK, and I think in other European countries, turning on a red light is an offence, even when you don't have to cross a stream of traffic to do so - I believe in the USA it's legal. And the same goes for overtaking on the wrong side of a vehicle in most circumstances, especially on a motorway.

And in Ireland, on many older roads which look like they are wide, but the outside lanes aren't really meant for driving, it is customary to pull over and drive temporarily on the hard(ish) shoulder to allow someone in a hurry to overtake.

(There'a a lot to be said for travelling by train and bus...)