It is a road tax from 2017 though. George Osbourne said so
Osborne said: "We will create a new roads fund from the end of this decade and every single penny raised in vehicle excise duty will go into that fund to pay for roads. The tax paid on people's cars will be used on the roads they drive on. It's a fairer tax system for motorists."
Therefore its not a vehicle excise duty based on emissions from then. Its based on using the road.
Osborne said it's not right that those who can afford new cars pay no tax while those who can only afford as used vehicle have to shell out for tax when both are using the roads.
So basically if you can afford a fuel efficent, low pollution car then you have to pay as much as anybody else as its based on road use not emissions anymore
Fair enough, my mistake.