Roads are funded through general taxation. The average family with income of more than £74,000 contributes about 27% of their income to government spending. The average family with income under £26,000 a year receives more in benefits than they pay in taxes. Low income families make no (net) contribution to government spending. An average family with income between £26,000 and £74,000 contributes about 15% of their income to government spending. All this is laid out here. (the numbers may be slightly different two years on, but I can't find anything more recent, and I am confident that the principle still holds).
In other words families with the highest incomes are contributing most to funding the road system. If we follow the principle that those who pay most have some kind of moral ownership of roads then nobody with household income under £26,000 should be allowed to use the roads at all, and those with income of more than £74,000 should be allowed to use them most.
Since 60% of households earn less than £26,000 it's obvious that limiting use of the roads to higher income groups could solve a lot of congestion problems. It would be a cheap way of boosting sustainable forms of transport, such as buses and walking, as well as cycling - all policy aims of our government.
I commend the idea to the house.
On second thoughts, perhaps not. Surely a gap between the value of services we receive from government and the amount we pay in taxes isn't some anomaly in the system - that's how it is supposed to work.
Footnote - what most people mean by "Road Tax" is actually Vehicle Excise Duty. VED is what we pay for the right to use a vehicle (not really - see Chris Hill's comment below), and has nothing to do with spending on roads. For what it's worth, fuel duties raise more than VED, but fuel duties have nothing to do with spending on roads either. Spending on roads is funded from general taxation. VED and fuel duties all go into the same pot as income tax, VAT ,and the rest. All this was decided way back in 1937. Before that there was a separate Road Fund. The case for the change was made by Winston Churchill (no less) - "It will be only a step from this for them to claim in a few years the moral ownership of the roads their contributions have created". Even though the system was changed the problem that he envisaged didn't go away - though "a few" years seems to have turned out to be about 70.