'Public' roads were not 'invented' for the public. They were not painstakingly funded and constructed by governments such that you or I could easily transport our chickens to market, or make it easier for us to paddle in the sea for a week.
The picture to the right is of a Roman road in Britain. It is now locally known as Blackstone Edge. The Romans would not have quarried the stone or laid any of it, but they would most certainly have overseen construction. They would not have used slave labour either. That would have been far too dangerous. The Romans left Britain around AD 43, and this road is a tribute to their knowledge and ability. You have to wonder how they cajoled the locals into doing this work.
For the public good? Maybe so, but it also enabled them to move troops around quickly if some of the population ever became restless. Unfortunately for the Romans, roads were not enough, resourceful Brits removing the cobbles to use as building materials for small domiciles, hence the lack of Roman roads remaining. They did the same to Hadrian's Wall, it being more important to keep warm in winter than stop marauding bands of Scots as the Romans had endeavoured to do.
The technology was not completely lost, and the Brits re-introduced cobbles later in their history. Cobbles, as pretty as they look are not ideal for road construction, being difficult to walk over in anything but dry conditions for humans and horses.
The breakthrough for transporting heavy stuff and men came with canals. The Industrial Revolution made possible chattels of war made from iron and steel, and the only way these things were ever going to be transported around the land was by using man made rivers, better known as canals. Yes, I know that commercial goods were the main loads carried, but make no mistake here. The primary use would have been to move military stuff.
Canals would have lasted longer had it not been for the adaptation of horse drawn, wooden railroads, to iron rails and the iron horse. However, both means of transport had a major drawback: the incline. Canals needed 'slow to operate' locks to get over obstacles, and railroads were dogged with iron to iron contact between wheel and rail, not good in wet or icy conditions, requiring the construction of cuttings and tunnels in a bid to get over the lack of climbing ability.
The invention of rubber tires, the steam/internal combustion engine and tarmac changed everything. They gave governments what they needed most, a reliable and easy way to move the military around while convincing the people to build them in the belief that it was for all good reasons like moving produce from one place to another.
Germany is a prime example of this. Hitler commissioned the 'Autobahn' system primarily to facilitate the movement of the military. Constructed in the 1930's, much of the system was so well laid down that it didn't need repairing for decades. This is in stark contrast to highways built in Britain during the 1960's and since, which have required constant repairs, sometimes only weeks after opening.
In fairness, roads in Europe and North America have been used more for commercial good than anything else, and we can be excused for forgetting the original purpose. So, what do you make of the picture below? It is a highway in a country where private vehicle ownership is virtually non-existent, where the movement of commercial goods is virtually non-existent by virtue of the fact that most of the people can't afford anything.
Remove the two vehicles and the cyclist, and what you are looking at here is a temporary airstrip or a road designed for moving either very large vehicles or masses of smaller ones packed with 'military'.
This is a highway near Pyongyang, North Korea. Imagine spending so much on a road which the public do not use. What were they thinking? Maybe something along the same lines as the Romans, almost 2000 years ago?