I somteimes drive minibus with a 62mph speed limiter. Its fine on the dual carriageway as you can just press the pedal full down & go without needing one eye on the speedo. It does mean the overtakes have to be considered much more carefully if you have no reserve.
Expecting a SatNav to control any limiter is not practical as they are not updated often enough to even take in permanent new limits never mind temporary ones. As others have said traffic sign recognition it not good enough either. There are people who would tend to rely on such systems totally & ignore the speed & actual signs. More work need on this one
