When I leave it on, on cloudy days, I find it takes a reasonable period of time before it triggers. Quick glances down or to the side such as looking at something out the side window do not trigger it. The only annoying instance is when I’m stopped at an angled intersection and I have to lean forward and to the side to check for an oncoming car. That irks me a little. But if I had a teenager driving I would highly value this, until they learned that all you have to do is put on sunglasses and you defeat it. That is if they weren’t able to just turn it off to begin with.