[hansvm]

We'd probably need a few other societal changes to make automatic enforcement of the posted speed limit manageable. As an example, if you're on a 50mph road in the USA and assume that your speedometer is calibrated within legal tolerances (and no further) then you'd have to set your cruise control to at most 43mph to ensure that you'd never speed (5mph speedometer error at that speed plus 2mph in speed variability from bumps/hills/etc), you could actually be averaging as low as 39mph in practice, and somebody else behind you with a speedometer off the other direction could think you're going as slowly as 35mph (on average, slower from time to time). I can say from experience that doing so is an easy way to be flipped off, sworn at, passed on the shoulder or a sidewalk, and have police called to your location (occasionally driving the speed limit plus 0-10mph results in similar levels of aggression), even though you can potentially be ticketed for going even a mile per hour faster (most police forces allow a lot more slop in your speed for precisely that kind of reason, but there are definitely a few who don't give a shit because they know you don't want to drive all the way back to the middle of nowhere to fight it) and even though driving that slowly is totally legal in most places.

None of that is insurmountable of course, and the easiest fix seems like just having the automated system only ticket you at some threshold above the limit while grandfathering in tighter speedometer tolerances. Aggression from driving the speed limit would probably decrease rapidly as tickets started arriving in the mail.