A note, because not everyone knows this: if you're driving and another driver flashes their brights at you, this is a signal to be on alert and slow down. There may be debris in the road, a cop out of sight, or an animal crossing ahead of you. (Or, alternatively, your brights are on and they're getting blinded.) Whatever the reason, it's a signal that you need to focus and reduce speed. And possibly turn your own brights off.
This PSA has been brought to you by the four fawns and does that ran out in front of me at various points on my drive home.
Let's court death with mama!
adding the tags for more relevant info
this is also true in the UK! a cyclist or motorcyclist will signal the same thing by tapping the top of their helmet.
Also if the vehicle in front of you puts their hazards on - they may be indicating to you that they can see something ahead you can’t, they may need to stop unexpectedly, or they may be about to do something else you won’t expect (for example, reverse park in the driveway on the other side of the road, so they need the other traffic to wait at a short distance while they complete the manoeuvre).
