From the information available the study did not specifically study those actually speaking on a mobile phone. Questions were directed verbally at the test person. What is the difference then between a conversation on a hands-free mobile phone and a driver and a conversation between a passenger and a driver. There are many other distractions, e.g. having the radio on, two argumentative children in the back of the car, etc. Should we not then insist that every driver is protected from these by a physical shield between them and any such distraction?