Why are retaining walls used in highway construction?

Retaining walls are specifically designed to support earth and stabilize slopes, making this the most appropriate answer for their use in highway construction. They are critical in preventing soil erosion and landslides, which can compromise the safety and integrity of roadways. When the terrain changes elevation, retaining walls can hold back soil, allowing for more effective land use and providing a stable base for highways.

These structures also help manage water runoff, reducing the risk of soil saturation that could lead to instability. While retaining walls might contribute to scenic views or drainage improvements in some contexts, their primary function is to provide structural support and ensure that slopes are stable enough for the safe passage of vehicles. Thus, their role in stabilizing earth and managing the forces acting upon slopes is essential in highway construction.