Length of Curve when Sight Distance is More Calculator

Length of Curve Formula:

\[ L_c = 2 \times SSD - \frac{200 \times (\sqrt{H} + \sqrt{h2})^2}{(g1 - g2)} \]

Sight Distance SSD:

Height of Observer:

Height of Object:

Upgrade:

Downgrade:

Length of Curve (m):

1. What is Length of Curve when Sight Distance is More?

Definition: This calculator determines the minimum length of a vertical curve when the sight distance is greater than the curve length.

Purpose: It helps highway engineers design safe vertical curves that provide adequate sight distance for drivers.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ L_c = 2 \times SSD - \frac{200 \times (\sqrt{H} + \sqrt{h2})^2}{(g1 - g2)} \]

Where:

\( L_c \) — Length of curve (meters)
\( SSD \) — Sight stopping distance (meters)
\( H \) — Height of observer's eye (meters)
\( h2 \) — Height of object (meters)
\( g1 \) — Upgrade gradient (%)
\( g2 \) — Downgrade gradient (%)

Explanation: The formula calculates the curve length needed to maintain safe sight distance considering driver eye height and object height.

3. Importance of Curve Length Calculation

Details: Proper curve length ensures driver safety by providing adequate visibility to stop or maneuver when encountering obstacles.

4. Using the Calculator

Tips: Enter sight distance, observer height (typically 1.08m for cars), object height (typically 0.6m), and grade percentages (upgrade positive, downgrade negative).

5. Frequently Asked Questions (FAQ)

Q1: What are typical values for observer and object height?
A: For cars: observer eye height ≈ 1.08m, object height ≈ 0.6m. For trucks: observer ≈ 2.4m, object ≈ 1.4m.

Q2: How do I input downgrade values?
A: Enter downgrade as a negative percentage (e.g., -3% for a 3% downgrade).

Q3: What if my sight distance is less than curve length?
A: Use a different formula for when SSD ≤ curve length.

Q4: Why is the difference between grades important?
A: The algebraic difference (g1 - g2) affects how quickly the vertical curve changes direction.

Q5: What units should I use?
A: All distance measurements should be in meters, grades in percentage.