In a new column, the BBC's environment analyst Roger Harrabin draws on his experience of a quarter of a century reporting the environment to ask if the government's transport taxes are unfairly penalising those people who use public transport.
CARS BECOME THE CHEAPER WAY TO TRAVEL
Will poorer people lose out to "green" road tax?
Contrary to popular opinion, driving is getting cheaper compared with other forms of transport, according to a report from the Commons Transport Committee.
The MPs say if the government is to hit its targets for reducing emissions, it has to prevent car use becoming even cheaper than using the bus or train.
But they say ministers have to be more open and honest about the purpose of road taxes.
They admit that there's such understandable distrust among drivers of the government's so-called green taxes on motoring that it is easy to miss some of the underlying truths.
One is that taxes on British motorists aren't very different from taxes on drivers in other European countries; that's when you look beyond petrol costs and take all road user charges, like road tolls, into account.
The other is that relative to the cost of using the bus or train. It's getting cheaper and cheaper to use the car.
Transport minister Paul Clark, responding to a parliamentary question from Lib Dem MP Norman Baker, said government figures showed that the real cost of motoring had declined by 17% between 1979 and 2008.
Yet, during the same period, bus and coach fares had risen by 55%, while rail fares had gone up by 49%.
The growing disparity creates a vicious spiral in which travellers reject buses because they're expensive; that reduces passenger numbers which forces bus firms to put up prices and reduce services, resulting in even more people using their cars.
The MPs say this trend has to be reversed if the government hopes to meet its environmental targets unveiled with a fanfare last week. Yet the government has a policy to increase rail fares 1% above inflation year-on-year and has no policy on bus fares at all, preferring - in Treasury-speak - to "leave it to the market".
In other words, policies on pricing (or non-policies) are running directly contradictory to the overall low-carbon strategy.
Green group Campaign for the Protection of Rural England (CPRE) echoes the committee's recommendations on the cost of public transport and point out that government policies will also put poorer drivers living in rural areas at a disadvantage.
In future, wealthy urban drivers will be able to buy electric cars and use them almost tax-free, while poor people in the countryside who can only afford old bangers will find themselves paying 8% more because of increasing "green" taxes on fuel.
It's another reminder that the challenge of creating a low-carbon economy are even deeper than suggested in last week's documents.
Another report on fuel poverty raises similar issues - for all its apparent joined-up thinking, transport and home insulation are two areas that clearly need fresh ideas.
More on green taxes in coming weeks.