You only have to show that people crash more often (or come close to crashing) when having a phone conversation compared to not having a phone conversation. You mostly cannot prove things 100% for a given accident as one cannot prove that the accident would not have happened without the phone conversation but if people crash more often in a simulator while being on the phone compared to not being on phone than it is obvious that being on the phone increases the risk.
It is all about what risk level is considered acceptable and how much outlawing something would 'inconvenience' people, about being proportionate. In addition, rules shouldn't be too specific or detailed, for once because the more specific a rule is, the smaller the data base is it is based on (and thus less reliable). It also makes it harder for people to obey the rules and it makes it harder to enforce it. It also makes it more likely to be out-of-date. A related aspect is general enforceability.
So to summarize:
- rules have to be proportionate to the risk and the 'inconvenience' they cause
- rule should not be very specific or detailed
In your examples, (2) is something which has a lower risk than talking on the phone and outlawing it would be considered to cause more 'inconvenience' than outlawing the use of the phone. (3) is way too specific (a: it is extremely unlikely that a single song has that effect but others don't and thus is almost certainly a rule with an extremely low 'cost'-effectiveness, b: has a very high 'inconvenience' factor.
The 'inconvenience' factor is to a significant degree subjective and is partly also based on a subjective risk assessment but it underlies lots of legal rules.
Those are good arguments for the case of outlawing an activity, and if the goal is to make us all safe(r), then that should be the course of action.
On the risk analysis, I'm with you. Texting while driving is far too risky, and the phone companies and the radio ads are making it socially unacceptable to do this. (I once saw a guy texting while driving a scooter. I think Darwin will take care of him...) Drinking alcohol and driving are dangerous, and the risk is too high for acceptability. In the early 80's, there was a social effort to make driving drunk "not cool", and the designated driver movement was born. Drunk driving was already illegal; making it un-cool was what really turned the tide on that.
However, if there is disagreement between us, I'd put it at where the line is, and have handsfree acceptable, and held to head (I do pull over... having an iPhone 6+ against my head and trying to drive is, well, difficult for me...) as a contributing factor in being pulled over, and not a direct factor. Hey, if someone can drive with a phone to their head, go for it.
The item 3 (and I did preface it as an extreme - thank you for reading it that way, was a way to show that there are limits to what we'll do for "safety" and reasonable legislative action. But heck, I may start back masking my Sports album...
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My state has a law against texting, not just a distracted driver law but one that specifically and explicitly prohibits smart phone usage while driving. I can safely say this law has zero impact on people's habits, I continually see people text and drive on major highways, surface roads and city roads. Nothing is changed and even if a law is passed for smart watches it won't do anything.
You cannot legislate common sense (to murder a George Washington quote).
Does that include
Jeff: "Hey Siri, Send text message to Mrs. thequick!"
Siri: "What would you like to say to Mrs. thequick?"
Jeffy: "I love you and I'll be home after I get out of jail for voice texting you."
(Yes, I know that people don't go to jail for texting... or do they?)
http://washington.cbslocal.com/2013/02/01/texting-while-driving-could-lead-to-jail-time-in-va/
