I think anything that can help to deter folks from distracted driving is a good thing.
That being said I have long held the opinion (and years later a college study backs this up) that it's not the fact that the driver is using one hand to drive, it's the total immersion in the conversation that causes the problems.
It's like this: when conversing in person we have the added benefits of body language and facial expressions to get our point across as a speaker. As an in-person listener we notice those body language and facial expressions and subconsciously use those in understanding and interpreting the speakers intent.
As a remote cell phone listener we don't see those subtle cues and focus intently on the speaker's word choices, voice inflections and other non-visual cues to understand and decide what the speaker is REALLY saying. Some of those vocal cues are lost due to the less than ideal audio quality of the cellular connection. And then as a remote cell phone speaker we work just as hard to get our point across using the same media with the same disadvantages.
What you end up with is two people engaged in a cell phone conversation , one or both them piloting a 4,000+ pound vehicle at 35 to 75 MPH in close proximity to other drivers, some of those drivers also engaged in a similar distraction and eventually the odds play out and you have an accident. Sure, the dialing and hanging up the Bluetooth-linked cell phone with buttons on the steering wheel help keep my eyes on the road but I still struggle at getting too focused on the conversation and not on my driving.
Of course, I understand people are different and some can possibly multitask better than others but that is NOT part of the driver's test nor is it a requirement for obtaining a driver's license.
IMO, being hands-free provides only some improvement...it's the immersion in the conversation that is the distraction for most people. I've been driving with one hand VERY frequently (75% of the time maybe?) for almost 55 years and have never been held at fault when rear-ended twice in traffic, my only 2 accidents in that period. And in that same period I have successfully avoided surely several dozen (or more likely hundreds) of red light and stop sign runners, lane changers, drunk drivers, items falling off vehicles, tires coming off 18-wheelers and countless dogs, cats, foxes, rabbits, 'coons, 'possums, deer, chickens, turtles and snakes. And I almost forgot...I have also avoided way too many people walking right out into traffic while using their cell phones.
