I don't know how to respond to your comment in that context.

Do you double-check your calculator all the time, to ensure it's not giving you the wrong answer?

As to Alec Watson's commentary about GPS, how do you know the area well enough to make judgements if you always follow the GPS routing which avoids the neighborhood?

If I spend a lot of time in an area I learn it and don't need gps to navigate it, however I might use gps just to find specific addresses as I don't usually memorize every street name. I also usually find that Google maps chooses perfectly sensible routes anyway, I don't see much point in trying to second guess it. Oh maybe I can save a minute or two or save a few kilometers by avoiding a highway, honestly who cares? I certainly don't. It will usually offer multiple route alternatives anyway, your ideal route or something close to it is probably among them.