What is the function of subgrade in highway construction?

The subgrade plays a crucial role in highway construction by providing support for the layers that are built above it, such as the base course and the surface layer. This support is vital because the subgrade is essentially the foundation of the highway, distributing the load of vehicles above to ensure stability and longevity of the pavement structure. A well-prepared and compacted subgrade minimizes settlement and deformation, which can lead to structural failures in the pavement layers over time. This foundational element sets the stage for the overall performance of the highway, making its proper construction and maintenance critical for a durable and safe transportation infrastructure. While drainage, cost minimization, and aesthetics are important considerations in highway design, the primary function of the subgrade is to support the weight of the upper layers effectively.