Clear Zone (AASHTO-style)

Lookup from Roadside Design Guide Table 3-1 style values with simple slope adjustments.

Reference only. Use current AASHTO Green Book/RDG and agency policy for design submittals.

Design/posted speed (mph)

ADT (veh/day)

Roadside slope

Logic: Base values from AASHTO RDG Table 3-1 (US customary) by ADT and speed. Slope classes apply small offsets per RDG guidance.

Offsets: +0 ft for recoverable 1:4+, +2 ft for 1:3–1:4, +5 ft for 1:2–1:3, +8 ft for <1:2/obstacles. Backslope/ditch keeps base value but check drainage/side slopes.

Reference table (ft)

Values mirror RDG Table 3-1 (ranges in feet) before slope offsets.