If you drive on the US Hwys you might see the driver, if his windshield is not dark.
If you drive on a divided highway you can't see the persons in side.
Years ago we only had a regular pickup or car, on a 2 lane highway, with no tinting. We could see each other.
What I try to do is flash my headlights. One Long, two shorts. That way they will not think I am trying to warn them about a local smokey.
This has been a topic in other forums that I read. Some say they don't want to take their hands off the steering wheel. I normally don't have a death grip on the steering wheel so I can use one of my hands. But if I wanted to go back about 50 years I could use my knee to steer
, stick my head out the window and wave with both hands
.
Yes if you see my Bighorn I might flash lights and/or wave.