Access to good roads is among the very few things that is so vastly important to the general prosperity of the population that leaving them to private companies would do more harm than good.

As the dude I overhead in some backcountry bar in the middle of nowhere put it: the government should pay for two things - clean water, smooth roads, and that's it.

Must not have been back into the country very far as water from a well doesn't need to be supplied by the government and rough roads keeps the outsiders outside.

I'd argue precisely because they are so important, is why I'm so sure the government should have its hand out of it.

I'd argue cars are the tragedy of the commons. Roads existed before cars, and they were for people and, yes, bicycles. Cars came and took them over, made them extremely unpleasant and unsafe places to be, require much more infrastructure and are much less efficient for short trips.