If cars were invented today, that's the one thing that'd probably change mechanically - a simple suite of sensors and a switch that shuts the engine down and engages the parking brake if the driver is drunk, fatigued or otherwise impaired.

That's been tried, but there's been no uptake. You could say, ok, have the government require it and that will solve the problem. We have seat belt laws, and breathalysers, why not mandatory automated breath testing before letting a car start? Well, here's something that various governments once tried, but it didn't last.

You don't have to be any sort of libertarian to understand that making people do what they ought isn't a magic wand. In democracies, the people who are making the people do what the people ought are, in the end, the people themselves. In the other parts of the world, you don't get to say what the government should make people do.