What's the point? Your ilk won't even accept government studies showing you're more violent. Why waste time trying to prove something else to someone with his head stuck up his ass? You don't even understand statistics and embarrass yourself every time you are shown them.
How would you quantify it? Being a bad driver doesn't mean you died in a car wreck, which is all stats can possibly show.
Here to satisfy your insatiable appetite for stats:
A study of nearly 100 million traffic stops from around the US has concluded that, on average, black drivers are 20% more likely to get pulled over than white drivers.
www.cnn.com
Considering you aren't pulled over unless you have probable cause it's safe to assume they're worse drivers. I've seen some horrible black drivers. Swerving all over the road, not using blinkers, etc. Yea whites do too, but for as few black drivers as there are compared to whites I see blacks much worse than whites. They also are much less likely to wear their seatbelts. How do I know? Because being 10 feet off the ground I can see into every car that passes me and I can see who wears their seatbelts most. And by far it's whites.