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A GPS device can be very useful, especially in the dark, in exurbia, when you’re trying to find an address. On the other hand, following instructions can lead to loss of navigational awareness. Some accidents have been caused by people following GPS instructions when they shouldn’t–onto railroad tracks for example.
Science Notes 
April 4, 2010 at 08:43
Hi Mona,
I agree. When we first got our GPS unit, I tried it out for routine trips around town. Its suggested routes would get you there, but never by what I considered the optimal route. It even once suggested a turn that would have resulted in a really awkward detour through a small Ottawa Valley town when our destination was right along the highway we were on.
In a strange location, though, I’d be fairly confident that it’d get you where you want to go, eventually.
βPer
April 4, 2010 at 14:15
I think that one problem is the GPS instruction set rather than the directions. It will say things like, “keep right to Exit 342” when what it really means is “continue along the highway in the right-hand lane,” even if that instruction is good for only a hundred metres and it then tells you to go left and stay on the highway. That’s especially disorienting when you’re only glancing at it once in a while so as to keep an eye on the traffic. I thought of those as the “next exit” instructions and made several wrong exits before learning to think critically and check frequently.
Another problem is that the instructions are done by someone looking at a map. They don’t know where one road changes into another and curves are sometimes taken to be the boundary, so you’ll be already driving on a road while the instructions tell you to turn left on it. I understand that the companies do take feedback and correct their maps, but it’s also probably important to get updated versions every year. For one thing. they don’t know about construction and will happily tell you to go through a road that has been closed for a year or two or take you on a long detour thinking that there’s a break in a road. It does generally get you there, but there have been a few accidents where people have automatically turned onto railway lines when instructed to.