In this case, it isn't fair - the externality is pollution, but the fee is unrelated to the emission levels of the vehicle. But even such an inefficient system is still superior to doing nothing and letting the public suffer the externalities.
An example: the Obama administration set forth a regulation that forces automakers to produce one 50 MPG vehicle in their line-up within the next five years. Of course, this is a stealth tax which has similar negative effects (and positive ones) to a higher gasoline tax, but the negative effects -- like higher car prices -- are less traceable to the mandate, which is good for politics. However, there are less obvious negative effects, like raising the barrier to entry for competition (it is no coincidence that the heavily regulated auto industry has very few startups -- Tesla being an anomaly.) A new company that only produces 30-45 MPG SUV models cannot compete, whereas it would be relatively competitive with a higher gasoline tax.
I think this sort-of ties into the political ideology where "luxury consumption" is bad. I.e. truckers transport Important Stuff(TM) and thus deserve a tax rebate on fuel, whereas a private person driving their own vehicle is bad, and should be discouraged.
But, the world changed (or, lets say the balance between the different taxes, incomes etc.) and at some point it started to make economic sense for the average Joe to buy a diesel car instead of a gasoline one.
But of course, changing the tax policy by getting rid of the diesel tax rebate runs into fierce opposition by the trucking/taxi/etc. lobby. So here we are.
It's because the issue they're directly trying to tackle is congestion, not pollution (which is only being tackled as a secondary issue). Also, in Britain there are already high petrol taxes, they make up about half the price of fuel. In general it's a good thing, and it does discourage a completely car dependent society - people to live closer to the centre, closer to work, use alternatives like walking, cycling, public transport etc - but it's not a particularly direct way to tackle air pollution, or at least it doesn't tackle the particular spikes in air pollution you get in the cities. In order to tackle air pollution in London using only fuel tax, you'd have to make driving in the countryside ruinously expensive. So you get layered policy - medium fuel tax nationwide, congestion charge for the centre (where it is the biggest issue), and an air pollution charge, or limit, covering the whole city.
I do agree that often politicians are not that great at designing these things (the proposed air pollution charge in London is rather strangely designed for instance), and the complexity is partly incompetence, but it's also partly because the problem is complicated.
Sweden, where the OP example comes from, is a relatively small political entity. 10 million people represented by 349 members of parliament, who are elected through a proportional representation system.
We have high gasoline taxes. Actually a carbondioxide tax and an energy tax. It also attracts VAT. In 2016 the petrol (95) price was 13,02 SEK / litre ($1.50) of what 8,64 SEK ($0.99) was taxes.
However, in Stockholm it wasn't enough to combat emissions and congestion. So rather than penalising all car travel across the relatively sparsely populated country, it seemed to make sense to have a toll at the city borders.
Everyone has brought up this point, but I think a higher city petrol tax would cover that.
Wouldn't that be the point? Low mpg cars are undesireable.
https://en.wikipedia.org/wiki/Fundamental_diagram_of_traffic...