Transport & space · 1820
Macadam road
Compacted layers of small broken stone make cheap, durable all-weather roads.
John Loudon McAdam's method, published around 1820, used angular crushed stone in thin compacted layers above well-drained subsoil. It was far cheaper than Roman-style paving and spread across Europe and America. Bound with tar, it became tarmac, the base of modern paved roads.