gradeline

noun

1. A longitudinal reference line or slope to which a highway, railway, or other infrastructure is built. It defines the intended grade or slope of the structure, ensuring proper drainage, safety, and functionality.

   “In valleys and depressions, embankments with side slopes of 1½ to 1, or about 33°, are raised to the grade line of the road; while the ridges and other prominences, occurring upon the route, are cut through to the same level, or grade line, leaving a surface width of 26 feet, and slopes upon the sides in the proportion of 1 to 1, or 45°.”

   “Some soils, however, have a high water table, bedrock, or other obstacles that must be considered before the position of the gradeline is determined.”

   “A good procedure is to first attempt to plot the gradeline on a topographic map, connecting the positive control points, and keeping the road at an acceptable grade.”