I have noticed that while driving in autopilot, as I come to a change in the speed limit, the car automatically changes the speed to match. If I'm driving 70mph and the speed limit drops to 55mph, the car automatically drops to 60mph. when the speed limit goes back up to 70mph, the car goes back to original 70mph speed by itself. The thing is, it doesn't do it all the time. I just recently noticed it doing this and think it's pretty cool. But other times I have to manually change the speed. Is there a particular thing I need to do to make it automatically change speed limits or is it just a fluke and happens when the car wants to do it?