Can someone explain why talking hands-free on a cell phone is more dangerous than talking to a person in the next seat? When you speak to someone in person, you

Can someone explain why talking hands-free on a cell phone is more dangerous than talking to a person in the next seat? When you speak to someone in person, you unconsciously glance at them to judge their reaction or confirm yours. With a cell phone, your eyes have nowhere to go but on the road. This part of the proposal seems like over-reaching, and appears ignorant of the fact that most new cars offer bluetooth cell phone connections and hands-free operation. In my own car, the phone on/off switch is in the steering wheel. Before this proposal is taken seriously I would like to see some data that compares hands-free cell phone activity with other common activities that distract the driver's attention and/or eyes and hands.