https://www.destatis.de/EN/Themes/Government/Taxes/Excise-Du...
https://www.statista.com/statistics/810662/passenger-cars-st...
https://www.zoll.de/DE/Unternehmen/Kraftfahrzeugsteuer/Steue...
> 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.
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[1] https://www.forschung-und-wissen.de/nachrichten/oekonomie/au...
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.
[1]: https://www.htw-berlin.de/forschung/online-forschungskatalog...
Maybe that is why.
Not all petrol or diesel is consumed by motor vehicles that (primarily) drive on the road.