I think you're over complicating things. I don't know what the definition of 'going over the limit' is in the US but in the UK it is 10% plus 2mph. This leaves

I think you're over complicating things. I don't know what the definition of 'going over the limit' is in the US but in the UK it is 10% plus 2mph. This leaves plenty of leeway for your emergency dash to the hospital at 5mph over the limit and the occasional lapse of concentration. I concede that you do already have severe penalties for reckless driving but they are not rigorously enforced except for extreme outlying cases and/or where a serious collision has resulted. And, I think, this is where the true solution may be found since more rigid enforcement of existing laws may actually be enough to deter all but the most determined of miscreants.