Sight Distance More than Length of Summit Curve Calculator

Sight Distance Formula:

\[ S = L_s \times N + \frac{(\sqrt{2h_1} + \sqrt{2h_2})^2}{2} \]

Length of Curve (L_s):

Deviation Angle (N):

rad

Driver Sight Height (h₁):

Height of Obstruction (h₂):

Sight Distance (S): m

1. What is Sight Distance More than Length of Summit Curve?

Definition: This calculator determines the required sight distance when it exceeds the length of a summit curve (crest vertical curve) in road design.

Purpose: It ensures drivers have adequate visibility to safely stop or maneuver when approaching the crest of a hill.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ S = L_s \times N + \frac{(\sqrt{2h_1} + \sqrt{2h_2})^2}{2} \]

Where:

\( S \) — Sight distance (meters)
\( L_s \) — Length of summit curve (meters)
\( N \) — Deviation angle (radians)
\( h_1 \) — Driver's eye height (meters, typically 0.75m ±5%)
\( h_2 \) — Obstruction height (meters, typically 0.36m ±5%)

Explanation: The formula combines the curve length component with the sight distance needed to see over the crest.

3. Importance of Sight Distance Calculation

Details: Proper sight distance ensures safe stopping distance, prevents accidents, and meets transportation design standards.

4. Using the Calculator

Tips: Enter the curve length, deviation angle, driver eye height (default 0.75m), and obstruction height (default 0.36m). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is driver eye height typically 0.75m?
A: This represents the average eye level of a truck driver, providing the most conservative (safe) calculation.

Q2: What does the obstruction height represent?
A: Typically the height of opposing vehicle headlights (0.36m) or other potential obstructions on the road.

Q3: When is sight distance more than curve length?
A: On steep crest vertical curves where the driver's line of sight is limited by the hill's curvature.

Q4: How do I convert degrees to radians?
A: Multiply degrees by π/180 (approximately 0.01745). Many calculators have this conversion function.

Q5: What safety margins should I consider?
A: Engineering standards typically add 10-20% to calculated values for safety buffers.