I have on occasion used a tactic to prevent cars from overtaking which doesn't sound like it should work, but seems to work 99% of the time. And what's more, it doesn't seem to irritate drivers in the same way that taking primary does.
The scenario is relatively specific, but happens a lot - you're coming up to some kind of pinch point, there's a vehicle behind you and you can hear from its engine that it's going to try to overtake and that, with the pinch point coming up, they have not realised that the speed the bicycle is going at, this isn't going to end well (for the cyclist, anyway).
What I now do when this situation is about to happen is simply to look over my right shoulder at the vehicle. Indeed, not even so much as turning my head right round, but merely turning it enough so that I can see him out of the side of my eye, much like I would when I'm glancing behind me, but keeping my head turned like that for a good couple of seconds. It helps that I tend to ride with sunglasses on, because this means I can actually continue to look straight ahead with my eyes, but the driver behind me doesn't know this and thinks I'm continuing to look at him.
What seems to happen is that the driver then slows down. Very, _very_ rarely does the driver continue with their manoeuvre. Indeed, I can't recall the last time the driver did this.
It seems an odd tactic that really shouldn't work, but for some reason, it does. Maybe the driver is suddenly thrown into the mindset that the cyclist, now watching them, is carefully watching whatever stupidity they are going to attempt *before* it happens, and therefore they think twice about doing it. I'm really not sure. But as I say, it seems to work.
Does anyone else do this, and finds it works the same way? If you've never tried it, I'd be interested in others trying it and seeing whether it really does work, or whether I'm kidding myself.