Like others said it's from others phones.  We were traveling to Bismarck from Iowa last year, holiday weekend, through the cities, not a good combo.  I wasn't using my GPS, I know where I'm going in the cities, and it's pretty simple after that.  All the sudden mom's phone gives different directions, we were traveling along no problems on the interstate. We took it, figured not much to lose, it was only 2 extra miles, routed us to a frontage road, we could see the backed up traffic solid for over 5+ miles, phone said it saved over 90 minutes, priceless when traveling with two kids under 4.  So I have mine on even in when I know where I'm going on the interstates or around big cities now.