Unless there is a transmitter somewhere along every road kicking out the speed limit for that thing to pick up, its running off a database of soemkind. Its probably just got the road "type" (i.e. residental, highway, etc etc) and displays a minimum speed limit for that type. I havent tried any gps software on the road yet because my carpc isnt fully functional, but ive read alot of guys talking about speed limits on their gps software. One person mentioned a annoying alarm that went off when he was speeding. That leads me to believe with the right software, you shouoldnt need the road angel, just more research on a good gps software.