This is called a speed limiter and I LOVE it in my Mercedes. I set the limiter to match the road's speed limit and I can just drive without worrying that I'll get caught speeding. No need to constantly look down at the speedo.
https://news.ycombinator.com/item?id=15095626
Probably did not wait long enough for the reply button to appear.
Though I'd check my ballast too, and probably read a book.