Earlier quoted context omitted.
Funding road repairs, construction, and expansion from general tax revenues is similarly subsidizing a different mode of transit, and it's likely a much higher value than the 3b€ you mention (and likely more than overall railway sector subsidizing, tho I'm not familiar with Germany's budget). Also recognizing that other positive externalities exist, but pricing them at $0, seems silly.
Aren’t roads necessary from a “last mile” perspective for like, all sorts of things a functioning country needs? Last time I checked trains don’t run directly from farms to grocery stores and so we need trucks and therefore roads in order to get food to consumers, among other things.
Yup, absolutely! But at least where I've worked on road design, the number of lanes on a local road is governed pretty much solely by the number of cars (trucks just have a larger impact on asphalt structure choices and, balance with the impacts of freeze-thaw, resurfacing schedule).
But this is about longer distance travel - trains generally being used for intercity travel vs highways. Even still, I don't argue against road subsidization, but rather in favour of more train subsidization.