> 2 car lengths at 80 mph is not ok.

Definitely. 2 seconds is OK, but 3 is better

All this would do is cause noise pollution. Have you never had the displeasure of riding with someone who will leave their seatbelt unplugged despite the annoying beeping?

People do this? I'd expect them to at least click the belt in and to sit on it. Personally I prefer to not die violently so I just strap in normally.

You could easily avoid the "noise pollution" by driving safely.

How can I make other people drive safely? I'm obviously not worried about myself, but about hundreds of others constantly triggering it and causing noise pollution.

It would only beep inside the car. So if other people are driving and it's beeping then they should drive better so they don't annoy their passengers (you).

The point of the beep is to get the driver's attention so they slow down. Similar to rumble strips on the side of the highway.

Ah, I see. "Beep" is a alt term for using the horn where I am from. I was imagining constant honking from hundreds of cars. An internal warning makes much more sense.