Anyone who has used Google Maps, GPS, etc. on routes they are familiar with will quickly realize they are all imperfect systems and should not be relied upon completely. Read a map in advance and use your common sense.

Garmin works best in my experience because it gives you plenty of notice and tells you which lane to be in. Nevertheless it's not perfect and sometimes recommends less efficient routes. Memorably it instructed me in Clearwater, FL, to make a left turn into oncoming traffic on a one-way road and in central Ontario suggested a road that if taken would have stranded me on a beach on Georgian Bay.