I wasn't subscribed to this thread so I didn't see previous replies until today, but it would be nice if people could discuss an issue without being rude.
As for how dangerous it really is when others can't see the driver--very dangerous. Just last week I would have been hit on my bicycle if I hadn't been able to see the driver. She was texting or something and stopped at a stop sign but never looked up at all, didn't look right, left, or straight ahead, just stopped then drove straight through. I had no stop sign and would have been right in front of her if I hadn't been able to see her. I turned right to avoid being hit. Similar situations happen to pedestrians and bike riders on a regular basis. It is much safer if one can see the driver.
Even for other drivers, how often have you arrived at a four-way stop and someone isn't sure who's turn it is, or is mistaken about whose turn it is? If you can't see the other driver they can't signal for you to go, and you can't tell if they are preparing to go. That could lead to an accident. Often it leads to drivers waiting and waiting to see what the invisible driver does, or the one who knows it's his turn starts going, but very slowly because they don't know if the invisible driver is going to do. There are many other situations where the invisible driver makes it more dangerous. How often do you see someone change lanes without signalling? You can sometimes see the driver looking and preparing for a lane change, so at least that gives you some warning to get out of the way.
Also, windows that are slightly too dark in broad daylight may be blacked out at night or in lower light situations. These windows can also make it harder for the driver to see what they need to at night--people, deer, cats, whatever. I understand that there is a comfort factor to blocking bright sunlight, but I think the safety of yourself and those you share the road with is more important.
And as a practical matter, an invisible driver cannot give any signals of helpfulness, apology, courtesy, or even those that some would say are very rude. And while our police are very busy, they do give citations for too-dark window tints, and it even gives them a clear justification to make a traffic stop when they don't have any other probable cause.
But I really understand the problem of being in situations where you need to swing the sun visor back and forth based on turns or curves in the road. I once had a car with dual sun visors and it was amazing. So simple, and could probably be done for $20 a car or so, but I'd pay a lot more for that feature. I don't understand why all vehicles don't have them.
To be clear, I'm not talking about the eyebrow tints when I discuss the dangers of illegally dark window tints.
