South Africa's Business Day has an editorial about the latest Budget which includes a ZAR0.30/l (US$0.02/l or US$0.08/US gallon). Most of it is for general revenue, and the question raised by the editorial is whether the fuel tax in the country is a "sin tax" to punish private motoring.
The position taken by editor Mark Smyth is that if people do not have reasonable alternatives to driving, then it is a penalty. However, he suggests that it would be preferable to ring-fence or hypothecate the new revenue, to address road transport issues. The controversy over the Gauteng Freeway Improvement Project tolls is what causes particular concern, because SANRAL (South African National Roads Authority Limited) had long insisted that tolls were necessary to pay for that project because fuel tax would not. Yet it appears the Government can increase fuel tax when it seeks additional revenue, which gives the not unreasonable impression that tolls are a specific target of users of the Gauteng highway network.
Fuel tax is an easy tax to collect, but if it is introduced explicitly just to collect revenue, it risks criticism simply because those who bear the greatest burden tend to be private motorists and road transport operators. Clearly, if it is directly related to expenditure on roads (as is widely seen in the United States) then it is seen as a user fee, so there is a direct link between what is paid and maintenance and improvements to the network. However, it may also be imposed as an environmental tax, incorporating a price of CO2 or factoring in the impacts of noxious pollutants on public health. Yet that has not been presented as a justification either.
The problem of fuel tax is that it isn't very good at advancing behaviour change. It is an ideal carbon tax, as the implicit generation of CO2 does not have a geographic specific impact, so can be imposed more generally (and fuel consumption largely reflects CO2). However, it is less than ideal as a pollution tax, because fuel consumption does not necessarily correlate to noxious emissions. It is a poor user fee to reflect infrastructure costs, not only because it does not discriminate by location, but it is widely understood by economists as a poor proxy for wear and tear generated by vehicle axle loads beyond around 8 tonnes Gross Vehicle Weight, as diesel consumption does not increase sufficiently to compensate for this.
Yet fuel tax has another problem, which is one of declining yields. As fuel efficiency improves, the amount derived reduces and this tends to create an equity problem as those who pay the most will be those least able to afford the latest most fuel efficient vehicles.
Given the controversy over tolls in South Africa, it would be timely for the whole field of motoring taxation and tolls to be investigated. I think there may be better scope to move away from tolls on some routes and move towards a wider network road user charging system that can replace some fuel tax and the need for geographically specific tolls. Whether this could be more acceptable is unclear, and of course it is critical that enforcement be addressed, but it would be more financially sustainable and may be more acceptable than location specific tolls.