I'm all for reigning in some of the larger stupidity we have around cars and transit, but we're never completely getting rid of single occupancy vehicles and the best route to nearly eliminating DUIs and pedestrian deaths is ultimately going to be driverless vehicles.
The follow-up to "we're never completely getting rid of single occupancy vehicles" should not be "let's put 0 occupancy vehicles on the road" which are not doing any useful transportation service, but are contributing to congestion, emissions etc.
Since it's pointless to come occupied vehicles (which have a person who will have a clear motive to remove the cone), the only ones being impacted are empty and _not_ carrying drunk or reckless otherwise-could-have-been-drivers.
It probably won't happen in most of the United States because most Americans don't want it to but it's not because it's an outlandish idea. It's the cheapest and most practical one.
