It would be a good start, until the automatic seatbelt was faulty somehow and then they couldn't use it. Unfortunately I don't think there's any way to get people to put on their seatbelts unless you make it so the car doesn't start if the seatbelts aren't buckled.

Been tried. Didn't work. Many of my cars have been from the early 90s. Some had "motor mouse" shoulder belts while others were attached to the door. The motor mouse belts occasionally lost their motor and the door-mounted ones rarely fit right, at least not for those of us tall enough to need the seat more than halfway back. Of course, every one I tried except one was in an American car and the one that was foreign (a VW ) was the only one to actually work, so.... Personally, I would rather go beltless than wear one that was 95+% certain to shatter my shoulder and less than certain to actually keep me restrained like a manual belt. Besides, all automatic belts have an emergency release that many anti-belt people use to avoid wearing a belt. The only car I ever had where that trick did not work was... the VW! If we teach the American carmakers to do things like the Germans and Japaneses did fifteen years ago then maybe it might work. However the odds of that are slim when you consider that they like to re-use designs (and machinery) from WWII. They are finally adapting to the 1980s. Maybe by 2020 it might be a good idea. Unti then....

No.

A valid thought, but not practical when you think about it in detail. I personally don't strap in immediately if I'm backing out because a) the law here says in reverse you don't need to be strapped in and b) it gives me the freedom to look around freely around the B and C pillars. If the vehicle didn't start without being strapped in or they were automatic then in my opinion backing up would be more dangerous. I backup a lot... Next there's the emergency situations. As an officer I'm sure there's been situations where you need to hop into your car and peel it around the block to cut off a fleeing fugitive. If you needed to strap in for that short jaunt you would lose precious seconds and maybe lose your eyeball on the runner. Of course not everyone has this kind of need but you said for all vehicles and that would include emergency vehicles. Then there's reliability. Automatic systems would need a few sensors and at least one motor. Given the current quality of most vehicles one could only imagine the recall notices, warranty issues, complaints, methods for thwarting the system, and problems with the belt not fully engaging and failing in a crash. I could go on but you get my point. If you don't want to wear one, fine. Just don't come whining to me when you go through the windshield. In the US it's easier because if you screw up you pay your own med bills. Up here it's an everybody pays system, so I hate that I'm paying for someones ignorance/stupidity/arrogance.