Actually,, no.
The question is,, " why do police exist at all?"
As far as the roads,, they existed before government. The role of government is facilitating free movement of goods and services, (trade) and the freedom of travel.. Maintaining roads should be local responsibility.
Roads started as foot paths,, and later horse paths or Cart paths,, and later the car.. NO one owned the roads,, they were used by all.
So, I ask again, why does the government own the roads? The role of government is not to facilitate anything. The role of government is to control.
I'm not sure how privatized roads would work. What would stop someone from buying 4 roads surrounding a neighborhood and trapping them inside? Didn't Carnegie once close down a huge railroad that a lot of people depended on because of a personal dispute? I think it was some railroad that went through NY, but I can't remember.
I just have yet to see a convincing argument for privatized roads that cover ALL possibilities. Like how competition would arise (you can't build over someone else's road). Also, every single road would probably have different rules, so every time you made a turn, you'd have to pull over and find out about the rules. Also, I'll say it again, but where would the competition come from? Without eminent domain, there would often only be a single possible road to travel to a certain place.
I think that we should keep roads public, but get rid of traffic laws and start replacing inefficient and costly traffic lights with roundabouts. Would save A LOT of money in the long-run. Also, while I HATE government spending in general, I think it would be a good idea to fortify existing highways to ensure that they don't need work done every year or two.
I don't know how they'd work, either. However, I know as a rule that competition is better than monopoly. If that's a given, then handing over control of the roads to the bureaucratic nightmare-monopoly of government seems totally backwards to me.
Your first scenario is a common objection to private roads. If you buy up all the land around someone and refuse them access to the outside world, it could be interpreted as an act of aggression. A siege, if you will. The besieger, as such, would be in the wrong according to the NAP.
I don't think your Carnegie example is fair or accurate due to the massive involvement of the government in establishing such monopolies in the railroad industry. Carnegie was very well-connected to government. Without government to prop him up (we can go into the feasibility of monopolies in a free market some other time), shutting down his railroad would have simply been an awful business decision if so many people were dependent on it. Now all those people will be looking for/interested in competition to his suddenly unreliable railroad, his workforce is angry for lost pay, he's lost money from being inactive yet still having bills to pay, etc.
If you want to see how it could work, do some research on the origin of turnpikes. In England and early US, turnpikes supplied high-quality, private roads in the stead of the rough paths crudely constructed and barely maintained by the governments at the time.
As for roads having different rules, it's kind of an absurd question. Don't you think it would be in the interest of road-owners if they streamlined it by agreeing to a common set of traffic rules? I'm fairly positive people could come to a solution without introducing government monopoly. The same goes for the introduction of competition - why do you consider eminent domain necessary to build roads? Why do you think monopoly and force are necessary or superior to voluntary exchange?
