1. What is Vertical Curve Length?

The vertical curve length (L) is the distance required to smoothly transition between two different grades in road design. It's calculated based on the rate of vertical curvature (K) and the algebraic difference between the grades (A).

2. How Does the Calculator Work?

The calculator uses the vertical curve equation:

Where:

• \( L \) — Vertical curve length (feet)
• \( K \) — Rate of vertical curvature (feet per percent)
• \( A \) — Algebraic difference in grades (percentage)

Explanation: The equation provides the minimum length needed for a smooth transition between grades, ensuring safety and comfort.

3. Importance of Vertical Curve Calculation

Details: Proper vertical curve design is crucial for vehicle safety, drainage, and driver comfort. It prevents sudden changes in grade that could cause visibility issues or vehicle instability.

4. Using the Calculator

Tips: Enter the rate of vertical curvature (K) in feet per percent and the algebraic difference in grades (A) as a percentage. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical K value for highways?
A: K values vary based on design speed. For example, a 70 mph highway might use K=247 for crest curves and K=193 for sag curves.

Q2: How is A calculated?
A: A is the absolute value of the difference between the incoming and outgoing grades (G2 - G1).

Q3: What's the minimum curve length?
A: Minimum length is typically 3 times the design speed (in mph) or 100 feet, whichever is greater.

Q4: When are vertical curves not needed?
A: When the algebraic difference in grades is less than 0.5% for low-speed roads or 0.2% for high-speed roads.

Q5: How does this relate to stopping sight distance?
A: The K value is selected to ensure adequate stopping sight distance is maintained throughout the curve.