Hands-free earphones deter drivers' safety

When people talk over the phone, they have to multiplex brain processing between driving on the road and talking to person on the other side. People definitely don't split brain's time 50-50. Depending on the conversation & traffic, the percentage can tilt either way.

Now, let's compare between phone_in_hand and hands_free. When you are holding the phone, you hold steering with the other hand. The driver's brain is already in an alert mode that he has to concentrate on driving to not run into an accident. With hands_free, people can easily get carried away in their conversations.

The point that the driver holds steering with two hands when using hands_free makes the situation less safe.