I do a lot of driving out in the forests and rural areas with GPS for navigation. I've noticed that I often need to be sure to set the GPS for Shortest Time rather than Shortest Distance. Setting the GPS to Shortest Distance can result in the GPS directing me via routes like 'Forestry Road #13' or worse.
The other thing I've noticed is that I can start a trip in town using my phone GPS and get directions to a rural location (actually hiking trailhead) and then on return be somewhere with no cell signal and be unable to get return directions.
I now travel with smart phone, stand-alone car GPS, and a paper map. I've occasionally had to resort to the paper map.