Some slope enables water to flow away from the roadway, but too much creates erosion.
Table 1 contains the recommended slopes for roads cross section, shoulders, and ditches for paved and unpaved roads. Slopes are described by the vertical rise or fall per unit of horizontal distance. Steeper slopes are usually expressed as a proportion. The most accurate instruments for measuring slope are theodolites and transits. Figure 1 shows the elements of a typical eye level.