Be careful doing that. There are quite a few locations where a quick flash or two of the highbeam is a "go right on ahead" to other drivers.
Very true, not so much in North America, but Europe and the UK, it means go ahead. I just leave my high beam on during the day, I'm a new street rider and that is one thing someone passed onto me at the MSF course. That plus a weave to the other part of the lane if possible usually gets people's attention.
On this particular incident, people day dream in their cars, I have had someone in a shopping lot turn in front of me(me in a car), no signal nothing on a two way lane!! The then girlfriend wanted to get go "get" him, I just shook my head!! Not worth it, too much to lose!