GIS. Geographical Information System. Basically databases off of geographic reference points. With enough connectivity you can pre-fetch the next legs speed limits. With enough ingenuity, you can get other cars to do it for you, Though you may want to look out for people inserting intentionally bad data.
Info lookup and storage is easy. The hard part is making sure it can't be tampered with or worked around (The first thing I'd do. Sorry. Yes, I have issues with authority.)
I strongly dissuade these types of things though as I'm intensely distrustful of centralized control infrastructures that allow for the potential implementation of effective "No Zones". Once you can tell everyone how fast to go where, you aren't that far from a system that can tell specific people's vehicles to only work going somewhere, or that they can't travel somewhere in particular.
>That would be totally impractical.
Which merely guarantees the development, deployment, and refinement of the approach against social untouchables and deplorables. Once it's in place though, that's when the normalization starts.
Construction speed limits are up to the driver to respect. It still makes sense to have these soft limiters to prevent inadvertent speeding. It would be a mistake to set the limiting feedback at exactly the speed limit rather then above the median speed for the sections of road which would only train drivers to routinely override the limiter feedback.
Also how does it handle temporary speed limits due to road works?