Source? Simpy by sheer logic the very act of using a navigation aid (phone, Sat Nav, map) must result in decreased attention to the mechanical process of drivi

Source? Simpy by sheer logic the very act of using a navigation aid (phone, Sat Nav, map) must result in decreased attention to the mechanical process of driving. I would challenge that safe navigation is a long solved problem. Who solved it? How? How was it measured? When was it solved - 2013? 2004?