I find myself in this position when I stop at an intersection. Looking at the driver across the way, I often mutter under my breath that it would have been helpful if he had used his signals so that I would know what he intended.
Then I look at my own dashboard and say, "Oops!"
Ha! Been there, done that, too, Bob.
When I get frustrated with folks I try to remind myself that there is no telling what challenges they might be going through, that might be causing them to do ____. Whether it’s in traffic, at the store, etc.