Macadam & Asphalt Roads

John McAdam's layered crushed-stone roads (1820s) and later tar and asphalt paving give all-weather road surfaces.

McAdam showed that a well-drained bed of compacted small stones carries traffic better than heavy foundations, and asphalt paving followed in the 1870s in Newark and Washington. Smooth sealed roads were a precondition for bicycles, cars and motorways.