Surely just makes more sense to scrap road tax and add a penny extra to the price of fuel at the pump, the current road tax system makes zero sense in my eyes. Tax people on usage and actually pump that money back into the system. The opposite of what they did with the railways, more expensive than its ever been to get the train to work.
They're forcing diesels off in London and all its done is let all us Northerners pick up a bargain diesel BMW. Probably be a nice export business if they continue down this ULEZ route.
Though saying all this, I still haven't seen an eco-friendly initiative take off from the various tax pots (VED, ULEZ, Congestion etc). Problem gonna be when they do it could be like these "smart" motorways all over again