Going to be a HUGE revenue drop from speeding fines and the speed camera companies will be going out of business.
That maybe so, but think of the revenue saved from not having high speed collisions, where they've got to pay for umpteen emergency services to help the wounded and clear off the roads, some reports say that it costs the UK economy £1million per hour for a major motorway closure. I would imagine the savings from that would far outweigh the loss in revenue from speeding fines.
Personally i think it's a great idea, there's already plenty of speed-limiting/speed-assistance systems on newer high spec cars these days, so it's just making that tech the norm for all vehicle types.
Frankly for anyone commuting in rush hour, you can't speed anyway due to volume of traffic. Now imagine how many extra cars will be on the motorways by 2030-2040.