My assumption is that they’d just be swept off with the wind and nothing else happening to them. But it depends if they hit the side of the car/the window frame once they go out, if they do, I assume it would end like the ones on my windshield, i.e. splat, if not, they just get accelerated to wind speed and once they are accelerated, it’s just like flying through 0 mph wind, even if relatively, they’re going 75 mph.