Cars with no rear lights
I don't know why but I'm seeing an increasing trend of more cars on the highway on night with their rear running lights completely turned off. It's a scary feeling approaching a car with no rear lights on at high speed. I've gotten a little closer than I wanted. Even with my headlights shining on them it throws off my whole depth perception. Their car seems farther away than it really is because you expect to see an equally bright glow like all the other surrounding cars. It's scary.
At first, I thought the drivers forgot to turn on all the exterior lights of their car, but that's not the case. Because their front headlights are clearly turned on.
I want to flash them so as to notify them, but that won't work. They won't know why I'm flashing them. They'll probably think I want to pass them. Although I cannot think of another way.