Do you flash on coming cars to warn them of a mobile speed camera ahead of them? Do you expect fellow motorists to flash you?
Nope and nope.
Not my problem and most people will read something else from it anyway.
I was disappointed not to be flashed by at least one vehicle in heavy oncoming traffic, over the recent Bank Holiday when I came upon a stealthily concealed copper with a speed gun.
Why?
Just like the horn, the flashing of high-beam lights is to advise other motorists of your presence. This is acceptable if you're being overtaken, for example, by a large HGV, as it lets them know they're past you and it's safe for them to pull in, which is why they're sometimes called Passing Lamps and the switch is sometimes labelled 'Pass'.
However, it has got to the point where people flash them under all manner of different situations, leading to things like the Flash For Cash types. IIRC, the Highway Code does specifically say you must not flash your headlights to convey any other message or intimidate other road users.
On top of all that, anyone flashing you oncoming would also be flashing the person in front of them, meaning further confusion.
So there's that, plus you technically shouldn't need to be told if there's a cop round the corner, as you're a good boy doing the correct, legal speed, right...?
Bikes certainly do offer warnings, but it's easier to do without using the headlights. Pointing diagonally up is usually a speed camera, while a thumb-down fist atop the head signifies a Police Officer (or similar).
Same as pointing down indicates hazardous road surface (ice, oil, gravel, etc) and a general palm-down patting sort of affair is a sign to slow down, usually because of some other hazard like a horse rider.
It seemed like younger people were disapproving, whilst older ones were shocked the younger ones found it odd or immoral! The funniest part was the most vociferous young detractor of flashing on moralistic grounds was the one who drove home after 4 or more pints <LOL>
