If ads jolt the driver awake because they're so jarring, doesn't that help with the staying alert thing? Though if the ads cause the driver to go into fits of rage, that's probably negative on the car being driven safely, though that would again help them with the being alert thing.

If driver alertness is the key factor, cars should have inward facing cameras that can detect the drivers eyes so it can play a horrible noise when the driver starts micro-napping. Or ads for nearby hotels. I think Teslas already have such a camera. New revenue stream!