I live in Charlotte as well. I have noticed this phenomenon on exactly one stretch of road. When going north on Providence Road from South Charlotte, the speed limit is 45 mph until you get to Sharon Amity. It then drops to 35 mph. While in AutoSteer, my car
recognizes the lower speed limit but does not lower its speed to stay only 5 mph above the new lower limit.
The road is 4-lane (2 lanes each direction), and there is a wide grassy median between the directions of traffic. It's not limited access, however--there are cross streets and a driveways on this stretch of road.
@foscoe944 , By the picture you posted later, it looks like you are on one of the many grassy median roads around town, too.
I suspect the navigation is mistaking that stretch for road for a limited-access highway. (Coded incorrect, maybe?) As soon as the grassy median ends just north of Wendover Road, the car immediately slows down to 40 mph (5 above the 35 mph limit). I've only tested this once intentionally. I think I had noticed it twice before, and immediately dialed the speed down myself. The time I tested it, there was no other traffic, and I wanted to see how soon it would correct its speed, and it corrected at the point where you would have guessed--where the median ended.
(Most people say this about their own city, but Charlotte drivers are horrible. I think using AutoSteer on straight, flat, lined city streets does make me safer than the majority of drivers on the road around here, because it forces me to only go 5 mph over the limit. Otherwise, I would probably find myself keeping up with traffic and doing 15 mph over. For comparison, I used to live in Chicago and visited recently, and the drivers there are much safer, on average.)