As I gain experience commuting by bike, I find myself getting better at identifying potentially dangerous drivers. Has anyone else noticed that one sure sign of a dodgy driver is headgear? If they're wearing a hat or a hood, they're almost always unpredictable, aggressive or inattentive; if they're wearing both, don't go anywhere near them!

Not sure why this is. To me it just seems wrong to wear a hat / hood in a car.

What other signals put you on alert?