The German gas tax is more like 4 times ours, and most of it goes toward the subsidization of the rail system, keeping the cost of tickets rather low, thereby encouraging use.
Why not total subsidization of public transportation (buses or trains) so that it is a free option?
Or is "just a little bit of socialism" the best model?
Boston's green line rail was free above ground outbound. Doesn't seem to have been abused.
If the goal is to get people to use it, this is what would accomplish that goal.
It also goes to subsidize Lufthansa. In any case, our highway system is so much more extensive that comparisons are hard to make.