I think you have that backwards. The text in the article was:

> they want to set the speed limit so that 15% of drivers exceed it and 85% of drivers drive at or below the speed limit.

The citation you provided is roughly consistent with that.

The original article also said:

> Lt. Megge believes the compliance rate in Michigan to be well under 50%.

That's the only part that estimates rates of non-compliance. And it's not 85%.

Actually, the article says “I’ve found that about 10% of drivers truly identify the speed limit sign and drive at or near that limit,”. That is what we were discussing here, not the 85/15 percentile thing. (Sorry I should have said 90% rather than 85%).

Of course the article doesn't say what those other 90% are doing. I suspect they aren't all breaking the limit - probably some are going slower than the speed limit.