How have people found speed assist to work? My understanding is that it is supposed to fall back to GPS data if it can't read the signs, but it also seems that it overrides GPS data if it thinks that it has successfully read the sign, even if the two values are quite inconsistent. For example, I've seen it misread an 80 as 30, and set the current speed limit as 30 despite that being an invalid speed limit (as far as I know) and extremely unlikely on a highway. It would presumably also be a large variation from what's listed in GPS databases. It also seems to have a lot of trouble reading the illuminated variable speed signs on freeways, almost always reading 80 as 60 or 'unknown' for example. In this case of course there may be no GPS values to fall back on, since the limit isn't fixed.