The ability-to-pay principle is one of the reasons for the general acceptance of the progressive income tax system.
The principle of user pays supports the idea of horizontal equity, which states that those in similar wealth and income positions should be treated equally by the tax system.
The divergence of user and beneficiary occurs when production and consumption have external effects.
In that case the user-pays principle results in the driver not paying the full or social cost of using fossil fuels, which creates a strong argument for regulation and other forms of public intervention.
However, such analysis is often complicated by the lack of knowledge that would inform regulators of the efficient level of gas use and the costs of emissions.