Crest Vertical Curve Length for SSD (AASHTO)
AASHTO minimum crest vertical-curve length L for a stopping sight distance, both S<=L and S>L branches, with the K rate.
Formula and source
L = A S^2 / C for S <= L; L = 2 S - C/A for S > L; C = 2158 (SSD crest) or 2800 (passing); K = L/A.
The AASHTO A Policy on Geometric Design of Highways and Streets (the Green Book) crest vertical-curve sight-distance minimums, by name.
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