What was unique about the roads the Romans built?

Answer 1

The Romans built the famous stone-paved roads. They dug the road bed down to the firmest level of ground or to the bedrock. Large amounts of materials found locally were used to fill the ditch up to one metre from the surface. This was then covered with gravel which was compressed to create a flat surface. The next layer was coarse concrete. Finally the stone slabs were embedded in fine concrete.

The stone-paved roads constituted about 20% (80,500km, 50,313 miles) of the total network of roads (400,000 kilometres, 250,000 miles) the Roman built around in the Roman Empire. The majority of the roads were earthen roads with a gravelled surface (via glareata) or plain earthed roads (via terrena).

The stone-paved roads had a military purpose. They made the movement of soldiers and the delivery of supplies to troops at the front or stationed in garrisons much easier and faster. They were also used for general travel and the transport of goods for trade. Their military nature was also shown in by the fact that they were usually built on a straight line, even when they crossed hilly areas. Traders who used these roads to transport their goods complained that the straight tracts over steep gradients made it very difficult for their laden wagons. After these complaints at least some of these tracts were redesigned to allow for less steep gradients.