Background - Our 2016 AP-1 configured model S 90D, has like other S and X owners, received a series of SW updates since last Oct., several addressing the autopilot feature. I have several complaints that I've communicated to Tesla about these so-called SW Autopilot improvements. The last three updates have progressively made AP functionality worse, then corrected (undo) in the following update, e.g. speed limited to posted speed, back to the +5 mph buffer limit, etc. In Tesla terms, any road that is not an interstate highway is a so-called "restricted road". That Tesla theory is great when applied to California's interstate system, but not great for many parts of the rest of country (off-the-interstate) and with expansive two-three lane open roads and wide shoulders that are posted 55 mph -- and with average traffic speeds that range from 50 - 70+ mph. Problem - V 8.1 (17.26.17) software update has significant problems in understanding the posted speed limits for sections of open roadways, especially 55 mph posted roads. Driving for miles under the AP-1 at the 60 mph limit for a 55 mph zone, and suddenly, without apparent reason the vehicle slows to 40 mph, and on the dash indicates that is the AP limit. No changes to road / traffic conditions or the posted speed limit, it just happens. Assuming the car behind hasn't already run into you, and you are able to manually correct the speed as needed, in my case, this condition continues under AP mode for several miles and then mysteriously jumps back to 60 mph or even 65 mph limit in several instances (which is faster than Tesla's self-imposed technology limit), and then self-corrects a minute or two later back to 60 mph. Not only is this sudden and unexpected automated reduction in speed dangerous, it's damn annoying. Has anyone out there experience a similar problem?