What is the purpose of a grade line?

The purpose of a grade line is to indicate changes in elevation, particularly in the context of highways or railways. This line serves as a crucial reference that helps engineers and planners visualize how the terrain changes over a specified distance. It allows for the planning and design of roads, ensuring that they follow the natural contours of the land or adopt the required slopes for safe travel. By understanding where elevations change, designers can make informed decisions on grading, drainage, and overall road design, which is fundamental for maintaining safety and functionality.

Other options do not accurately reflect the primary function of a grade line. For instance, while property boundaries are essential in defining land ownership, they are typically marked by survey lines, not grade lines. Aesthetic aspects of a project are more related to design features than to structural elevation. Additionally, outlining a building's exterior relates to site plans and architectural drawings rather than to the grade line's specific role in elevation changes.