Germany spends some 70 billion euros maintaining the road system, only about a third of which is offset by taxes on drivers [1]. If we accept that investments in roads reduce carbon emissions by 0 million tonnes per year, then that works out to NaN € per tonne -- much worse than other carbon abatement methods!
Naturally there might be other positive externalities to owning a car, but I don't own a car and therefore wouldn't be privy to them. Instead I rely almost exclusively on Germany's public transport for my daily commutes, which I find perfectly satisfactory for this purpose and significantly more convenient than parking and maintaining a car.
A third can't be right. 15 billion from petrol and 18.2 billion from diesel alone make up almost half of that. 48.76 million vehicles times €100 (back of the envelope calculation) for vehicle tax puts that number above half.
From the article (sorry for the bad link before; fixed below [1]):
> The revenue from taxes and levies on road traffic amounts to around 50 billion euros annually. Around half of this is earmarked by law via the mineral oil tax, i.e. around 25 billion euros. This means that just over a third (36%) of the earmarked revenue from road traffic covers the costs of roads and other facilities such as parking lots and the like. It is therefore clear that the public sector is heavily subsidizing road traffic.
My understanding is that these two forms of taxes add to more than 50%, but then almost half of those taxes must be reinvested elsewhere by law (i.e., not into roads), hence the 1/3 figure. But even if you ignore this reallocation of taxes, you still have a deficit of around 20 billion euros.
That's because the selection of numbers is a little bit weird. The 70 billion on the cost side are composed of 38 billion for construction and maintenance, 14 billion for traffic police and 18 billion for public funds spent for accidents. The generated income is only taxes on fuel and the tax car owners have to pay.
If you include the cost of the traffic police, there is way more stuff that you can include on the income side like taxes on car sales and part of the cost comes also back to the government in the form of taxes. There is likely also a large part of the costs that is missing. Doing this properly is a lot of work and doing it precisely is hard to impossible. These sort of things almost always include estimates for the higher order effects.
Btw: I googled the study[1] and apparently it was funded by the "Netzwerk Europäischer Eisenbahnen e.V." (Network of European Railways Association). I would take any statements and numbers with a huge grain of salt.
Maybe in UK local roads are funded differently? If you counted only national roads in Poland it would seem that Poland takes more in revenue than spends on roads, which isn't true if you count expenses on all the local roads that aren't in national budget.
Even if you don't drive a car yourself you depend a lot on things delivered by road. Most of the road wear is done by trucks bringing you food, construction materials and whatever else. You can't exactly replenish your local grocery store by rail or cargo bike.
Most of the need for roads though is cars. It is rare to see a multi-lane road where trucks are restricted to only 1 lane and cars allowed the rest - if though trucks wouldn't fill that single lane and in turn the other lanes could be built much cheaper. (in part because the road needed for a car isn't that much cheaper than the road needed for a truck - labor is about the same, and weather is often a large factor)
Naturally there might be other positive externalities to owning a car, but I don't own a car and therefore wouldn't be privy to them. Instead I rely almost exclusively on Germany's public transport for my daily commutes, which I find perfectly satisfactory for this purpose and significantly more convenient than parking and maintaining a car.
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[1] https://www.forschung-und-wissen.de/nachrichten/oekonomie/au...