Can you elaborate on what you're referring to?

When I hear the term 'brain freeze', the first thing that comes to my mind is the infamous ice cream headache that we all know and love.  Interestingly, if you take cold showers and the water is cold enough, the same effect can be triggered.

The other thing that comes to mind for that term is the temporary lapse in memory.  Sometimes called a brain-fart.

But with your mention of incapacitation and being a potential danger on the road, I don't think either of these apply.

Ah, gotcha.  I can only speak to my own experience.  I'm sure there's some variation in what people feel.

As I'm sure you're aware, it's usually caused by eating something cold very quickly.  The most common trigger I've probably had is chugging down an ice cream milkshake too fast.  It just feels like a sharp intense headache at the top of the forehead.  It's not pleasant, but it only last for a few seconds.  It's not any more distracting than other pain, so it's not incapacitating.  And no more dangerous to driving than a cramp or something like that.  The real danger would be from someone consuming something cold really fast to trigger the brain freeze while driving.  Which would mean they're not watching the road.

If there was a way to do it, I'd like to see ice-cream headaches caused by texting while driving.  That would stop people from doing it.