But why do you want to adjust all the roads in the country where maximum speed ever is 90mph, at least in the USA? Just pass the law to limit cars from driving faster than that, and problem solved!

It always amazes me how cars commercials show awesome dashboards with 250 mph speedos, perfectly knowing there is no single road that you can lawfully go that fast.

Heck, it probably won't cost much more than a thumb drive to stick into your car computer port to update speed limits built in.