Utilize our specialized calculator to determine the vertical curve length required for adequate passing sight distance (PSD). This essential tool helps civil engineers and roadway designers ensure safety and compliance with AASHTO standards, optimizing highway design for crest vertical curves. Input key parameters like grades, sight distance, and heights to get instant, accurate results.
Formula:
Vertical Curve Length (L) Calculation
The calculator determines the vertical curve length (L) based on the input passing sight distance (S) and other parameters, applying the appropriate AASHTO formula for crest vertical curves.
Key Variables:
- L = Length of Vertical Curve
- A = Absolute value of the algebraic difference in grades (in percent, e.g., 2% for a +2% and -0% grade difference)
- S = Passing Sight Distance
- h1 = Driver's Eye Height (standard: 3.5 ft or 1.08 m)
- h2 = Height of Object (for passing, often 4.25 ft or 1.30 m for an opposing vehicle, or 3.5 ft/1.08 m)
Formulas Used:
Case 1: When S ≤ L (Sight Distance is less than or equal to Curve Length)
L = (A × S2) / (100 × ( √(2h1) + √(2h2) )2)
Case 2: When S > L (Sight Distance is greater than Curve Length)
L = 2S - (200 × ( √(h1) + √(h2) )2) / A