What specific type of road surface is made of layers that bend a little and spread the weight of cars over a wider area?

The specific type of road surface described is flexible pavement. This type of pavement is constructed from multiple distinct layers designed to work together. At the bottom, it rests on the prepared natural ground, known as the subgrade. Above the subgrade are typically one or more layers of granular material, such as compacted crushed stone or gravel, forming the subbase layer and the base layer. These granular layers provide foundational strength and contribute significantly to spreading the load. The uppermost layers, which form the actual road surface, are made of bituminous material, most commonly asphalt concrete. Asphalt concrete is a mixture of aggregate (like stones and sand) bound together by bitumen, a sticky, black, petroleum-based substance. Because of the inherent properties of bitumen, the asphalt concrete layers in a flexible pavement are designed to be somewhat pliable. This means they can bend or deform slightly under the weight of traffic, a characteristic known as viscoelastic deformation, without fracturing like a rigid material. This slight yielding allows the pavement to absorb and distribute stresses more effectively. Furthermore, each successive layer of the flexible pavement plays a crucial role in spreading the concentrated load from a vehicle's tires over an increasingly wider area. The asphalt concrete surface distributes the load to the base layer, which then further disperses it to the subbase, and finally to the subgrade. This progressive load spreading reduces the stress on the underlying natural ground to a level it can safely support, preventing premature damage and ensuring the long-term integrity of the road.