It’s hard to find a hollow log in Canberra, but one exception is fuel tax credits. Fuel tax credits are worth $8 billion a year to the businesses that receive them, but only about half that outlay is justified in economic or social terms. The credits are gnawing away an ever-growing share of fuel tax revenue: a decade ago, they reduced gross fuel tax revenue by 30 per cent; today, it’s almost 40 per cent. Winding back the credits could reduce the structural budget deficit by about 10 per cent, or $4 billion a year.

Fuel tax is currently imposed at a rate of 48¢ a litre – but not all fuel use attracts the charge. No fuel tax is payable for vehicles that only drive off-road, such as trucks on mine-sites, or for other off-road uses such as in heavy machinery, and for heating and cooling. And a reduced rate of fuel tax is payable for on-road vehicles heavier than 4.5 tonnes, such as semi-trailers, B-doubles, and passenger buses.