Should non-autonomous vehicles be banned from motorways?

[5lab]

Before I get lynched, I don't mean yet! There is a story about no more ICEs after 2030 - should manually-driven cars be banned from the motorways by a similar date? Autonomous cars are more accurate, and faster reacting than human driven cars, but they work best in 'controlled' environments (ie : not so good with pedestrians, snow, unknowns, etc). Running only autonomous on motorways could mean :

Higher running speeds (say 100mph)
shorter distance between cars (say 1m, maybe bumper-to-bumper - reaction speed to brake lights is essentially zero, could even be transmitted wirelessly between cars)
narrower lanes (cars could be mirror-to-mirror - say 5 lanes in the space of 3)
no hard shoulders (where they still exist)

those things together would triple the current motorway capacity (66% more cars due to the lanes, 30% more cars due to the speed, twice the cars due closer running). No-one 'likes' driving on motorways, and there's no-where you can't get to if you're banned from motorways (a/b roads run along side all of them) so people with older cars can still get there.

Motorways were originally built to increase speed verses a normal road by banning some sub-sets of vehicles. Maybe its time to plan for updating those rules? The money being spent on upgrading the existing road infrastructure (smart motorways etc) could be saved and spent on better things. A current 2 hour slog in the rush hour round the m25 @ 30mph could become a 36 minute whizz, reading the paper the whole way