In order to replace road tax a levy of a further 18 to 20 pence per litre would need to be added to every litre of fuel, which is currently subject to duty and VAT of around 70p per litre.
I fear another outcry would result.
Finally we need to consider low emission engines and the road tax benefits they receive. This accounts currently for around £90 million in lost revenue. As electric vehicles replace the internal combustion engine variety the revenue loss increases dramatically. In theory if we all changed to zero emissions vehicles tomorrow the revenue deficiency would be around £34 billion per year. Expect taxation of electricity supplies to follow