The Romans started by clearing vegetation and driving a level trench along the chosen line. They then placed a layer of stones at the bottom, covered these with a layer of broken stones, pebbles, cement and sand that formed a firm base. On this went cement mixed with broken tiles and then finally paving slabs that were cut to fit together snugly. Either side of the road was a drainage channel to draw water away.
The modern roadbuilder likewise starts by removing vegetation. Soil is then cut away and compacted with heavy machinery to form a base course. On the top of the structure goes a smooth waterproof wearing course of asphalt (black top) or concrete (white top), the purpose of which is to prevent moisture getting into the structure.
The road is given a convex lateral surface known as a camber, to allow water to drain away to the edges where it is carried off by gutters and drains.