You would have to be smarter about it than wait for local gov. Vision systems that can read street signs. etc. OCR on street signs should be pretty easy since they use High contrast simple fonts.

OCR doesn't solve the problem of blind corners. In fact, even the current preemptive braking systems depend on radar, which perform poorly around corners.

Who said anything about blind corners? I would think it cool if like my GPS system my car knew the speed limit(and reading street signs in combination with storage would allow it to be correct, up to date and cover more roads than my rinky dink GPS system). sure it wouldn't know the speed limit the moment I turned a corner if it just relied on ocr but it might catch a speed limit sign I missed.

Right now all the telematics stuff is broken in to pieces you could do a lot of neat stuff if they were better integrated. You could use that preemptive braking stuff to decide I am in traffic on an interstate an find a new route.(Hint if the speed limit is sixty and I am with in a few feet of the guy in front of me and my current speed is below 5mph I am in traffic and the gps system should reroute me.)