Crest Vertical Curve Length Calculator

Vertical Curve Length Estimator

Input Fields

Sight distance

S

m

Initial roadway grade

g₁

%

Final roadway grade

g₂

%

Driver's eye height

h₁

m

Object height

h₂

m

CalculateReset

Calculate automaticallyIf enabled, the result will update automatically when you change any value.

Your Results

Minimum curve length

Minimum curve length

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Crest Vertical Curve Length Formula

\[\text{If } S < L_m: \quad L_m = \frac{A \cdot S^2}{200 \cdot (\sqrt{h_1} + \sqrt{h_2})^2}\]\[\text{If } S > L_m: \quad L_m = 2S – \frac{200 \cdot (\sqrt{h_1} + \sqrt{h_2})^2}{A}\]

Where:

• $$L_m$$ = minimum length of crest curve (m)
• $$A$$ = absolute grade difference (%), $$|g1 – g2|$$
• $$S$$ = stopping sight distance (m)
• $$h_1$$ = driver’s eye height (m)
• $$h_2$$ = object height (m)

Crest vertical curves are used in road design where two opposing gradients meet. These curves must be long enough to provide clear visibility for drivers. The equations differ depending on whether the stopping sight distance S is less than or greater than the curve length $$L_m$$. This calculator supports quick estimation for engineers, enhancing road safety and compliance with geometric design standards.