Cross drainage culverts are defined as those conveying drainage across and beneath the highway. Selection of an appropriate end treatment is primarily related to culvert size, culvert end location, side slope rate, terrain characteristics, drift conditions, ROW availability, and other hydraulic considerations that may influence treatment selection at individual sites.

Roadside safety performance is related to clear zone width and side slope rate. For a discussion of safety performance and design guidelines related to side slopes, see . Where ROW availability and economic conditions permit, flatter slopes may be used.

Design values for 4R clear zones are shown in for new location and reconstruction projects. Within the clear zone, side slopes should preferably be 1V:6H or flatter with 1V:4H as a maximum steepness in most cases.