[0] - http://www.ibtimes.com/texting-drivers-take-eyes-road-5-seco...
A given driver on a given trip is well-shown to be more attentive to traffic and less disruptive if you deny them distractions. (conversation, radio, food, etc)
But it seems plausible that a lost driver is a special case and may be less attentive and more disruptive to traffic if you deny them a navigational aid.
Anecdotally that feels true, though I don't know if it's been studied specifically.
Also, I don't know about you, but I don't have to think much about eating, compared to carrying on a conversation or reading.
http://www.bbc.com/news/uk-england-suffolk-19597446
http://news.bbc.co.uk/1/hi/magazine/4788910.stm
http://m.bbc.co.uk/news/uk-england-humber-22290619
Etc etc