Saudi roads authority details engineering layers of national road network

The General Authority for Roads has revealed the engineering details of the layers that make up the Kingdom’s road network, stating that roads consist of four main consecutive layers of soil, gravel, and asphalt, each differing in thickness and structural function. This initiative is part of the authority’s efforts to improve the quality of the road network, which is considered a key enabler for achieving the goals of Saudi Vision 2030.

The authority explained that the layers start from the bottom with the subgrade layer, which has a maximum thickness of 30 cm. This foundational layer is built from gravel and sand without organic materials, and must meet specific requirements to ensure stability and withstand heavy traffic loads.

Above the subgrade is the granular base layer, with a thickness of up to 30 cm, made from high-quality gravel materials. This layer distributes traffic loads evenly across the lower layers.

The authority added that the asphalt base layer follows, with a thickness not exceeding 20 cm. It helps reduce pressure on the foundational layers, improves water drainage, and protects lower layers from moisture damage. On top of this is the asphalt surface layer, with a thickness of no more than 5 cm, which is the uppermost layer exposed directly to traffic. It is designed to withstand pressure and weather conditions, providing a smooth and safe surface for road users.

Layer thickness varies by technical specifications

The authority noted that these thicknesses represent the approved maximums and may vary according to the technical specifications of each road, taking into account the intended use, traffic volume, and the site’s environmental and geographical conditions.

Expanding adoption of modern standards

The General Authority for Roads affirmed its ongoing efforts to expand the application of modern technical standards to improve the experience of road users and ensure the highest levels of safety, efficiency, and sustainability. It also highlighted its commitment to providing a unified and transparent legislative and regulatory framework, including the launch of the Saudi Roads Code, as part of its role in supervising and regulating the road sector in line with the goals of Vision 2030.