What type of slope is defined as the measure of elevation change over distance?

The concept of slope as the measure of elevation change over distance is commonly referred to as "gradient." In this context, gradient refers to the ratio or expression of the vertical change (elevation) to the horizontal change (distance). It is typically expressed as a percentage, indicating how steep a surface or path is by showing the rise over run.

Understanding gradient is crucial in highway construction and design because it affects factors such as drainage, vehicle performance, and safety. For example, a steep gradient may cause vehicles to experience difficulty, impacting their ability to ascend or descend safely.

The other types of slope mentioned have different specific definitions and contexts. Longitudinal slope typically refers to the slope of a roadway in the direction of travel, while cross-slope refers to the slope across the width of a road, which is important for water drainage. Vertical slope might imply the change in elevation without a direct reference to the distance aspect. Thus, gradient properly encapsulates the definition based on elevation change relative to distance.