Vertical Curve Length Passing Formula

Equation for calculate vertical curve length passing is,

L_m = [ S² × (g₂ − g₁) ] / 864 ∀ S<L_m
L_m = 2S - [ 864 / (g₂ − g₁) ] ∀ S>L_m

Where,
L_m - Minimum Curve length    
g₁ - Initial grade    
g₂ - Final grade    
S - Passing Sight Distance