What aspect of a vertical curve is expressed by the formula L = (g2-g1)/r?

The formula L = (g2 - g1)/r is used in the context of road design and geometry to express the length of a vertical curve in relation to the change in grade (or slope) and the radius of the curve. In this equation, 'L' represents the length of the vertical curve, while 'g2' and 'g1' denote the grades before and after the curve, respectively. The variable 'r' indicates the radius of curvature.

When designing vertical curves, especially on roadways, it's crucial to ensure that the transition between different slopes is both safe and comfortable for drivers. The formula illustrates how the length of the curve is determined by the amount of grade change and the curvature's radius. This relationship helps engineers calculate how long the vertical curve should be to achieve a smooth transition. Thus, the correct answer accurately identifies the primary focus of the formula, which is to express the length of the vertical curve.