The problem with talking on a cell phone while driving is that you are concentrating on the call and not what is going on around you...
Talkers stare directly in front of their vehicle and do not look behind nor to the sides, they typically slow down and have no clue of what is going on around them.
I know many people that do this and have yet to find 1 that will admit it hinders their driving. They will all say that they drive fine, although some have admitted to missing turn offs... I tell them you merely think you drive good while talking, however if I videoed you from another car you would see the problems that you create...
How many vehicles does it take to make a traffic jam?... just 1...
In years past it was playing with the radio, conversation inside the vehicle, smoking, eating, site seeing, day dreaming... Now we add the cell phone... All are distractions... Most can only concentrate on 1 thing at a time, although they are incapable of admitting or understanding it...
It is like the driver that drives the speed limit and believes they are a safe driver by doing so, yet they are often the ones to pull out in front of you in a quick move...
Safe driving requires more than merely driving at or below the speed limit...