>...roads already exist and maintenance is extremely cheap. It’s paid for with gasoline taxes.

According to [0] no state derives more than 71% of its "State & Local Road Spending" from gas taxes. Unclear to me what proportion of the spending is maintenance though.

The best number I could find for maintenance cost was [1], which says in 2015, the average per-mile maintenance cause of US roads is $28,020.

Can anyone help find a comparable figure for rail maintenance?

[0] https://taxfoundation.org/states-road-funding-2019/ [1] https://azmag.gov/Portals/0/Documents-Ext/FLCP/Roadway-Maint...