The Natural Philosopher a écrit :
I believe modern satnavs can do this and 'know' what (nearly) all the speed
limits are...

Only use I have come up with for satnavs so far..

My satnav can bleep at you when you exceed the limit, if you enable it.
Trouble is, the change limits more often than they revise the maps, so
its easy to get caught out - better to always use the eyeball, with the
satnav as a backup.