Man of Honour
They won't need a black box. Technology has reached a stage where number plate recognition could do most of it. The technology is here, unlike in the 90's. So this will almost certainly come in at some point.
Except the ANPR cameras are only on main roads, so the first Unintended Consequence would be massive congestion on minor roads as people tried to beat the cameras.
Depends on the total amount of fuel it uses, which is the entire point.
