I don't believe so; since if you think about it, there are different speed limit for different roads. There is no way to differentiate that unless all the roads are installed with transmitters of that information.

In all cases, you should slow down though. 10mph above speed limit is more than 'adequate' for most cases. I read a survey somewhere that Highway patrol will usually let you go up till 12mph or so. Then, they'll smack u with a ticket. Depending on the officer though of course.