I have a sat nav and I wouldn't dream of leaving home without it unless I was just popping to the shops or somewhere local. It tells me the traffic conditions and the fastest route, where the speed cameras are and warns me of them and tells me at what time I will arrive at my destination among other things.
However, what it doesn't tell me is the width of the roads en route or the height of any bridges. The width of narrow roads are almost invariably shown on signs at the entrance to it and there are height indications for bridges as you approach them on every road.
So why oh why do people blame their sat navs for 'sending ' them along narrow roads, down farm tracks, into rivers and along railway lines etc? Why are these people too stupid to take their eyes off the sat nav and look at road signs?