Final answer:
Macadam roads, developed in the 1800s, used well-drained soil beneath crushed stone pavement to create more stable and durable roadways compared to previous unpaved versions.
Step-by-step explanation:
"Macadam" roads refer to a style of road building created in the 1800s; they were innovative because they utilized soil underneath the road that was well-drained, providing a more stable foundation for the pavement made with crushed stone. This method, developed by Scottish engineer John McAdam, was a significant improvement over the unpaved roads of that time, which were often difficult to travel on due to weather conditions. Prior to macadam roads, Roman roads were the benchmark for durable infrastructure, having been built with concrete and stones to connect various parts of the Empire, facilitating military movement, trade, administration, and cultural assimilation within conquered territories.