Superelevation
Compute superelevation rate from AASHTO e + f = V²/(15R) with design friction defaults.
US customary units. Use current AASHTO Green Book values and agency limits for design.
Equation: e + f = V² / (15R). Speeds in mph, radius in feet, e and f in decimals. e is capped at your chosen max.
Outputs: Required e, adopted e (capped), friction used/available, and min radius if you hold emax and design f.
If friction demand exceeds design f, consider raising e (if allowed), increasing radius, or lowering speed.
Design side friction f (typical AASHTO)
Used when “Use design f” is selected. Pick a custom f if your agency differs.
MDOT Standard Plan reference: Superelevation runoff and max e detail.