1. What is Sight Distance Given Angle Grades Calculator?

Definition: This calculator estimates the sight distance on a vertical curve based on curve length, driver eye height, obstruction height, and grade angles.

Purpose: It helps transportation engineers and road designers ensure adequate visibility for drivers on vertical curves.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Sight distance (meters)
• \( Ls \) — Length of vertical curve (meters)
• \( h1 \) — Driver's eye height (meters, typically 0.75m)
• \( n1 \) — Positive grade angle (radians)
• \( h2 \) — Height of obstruction (meters)
• \( n2 \) — Negative grade angle (percentage)

Explanation: The formula combines the curve length contribution with the visibility components from both upward and downward slopes.

3. Importance of Sight Distance Calculation

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

4. Using the Calculator

Tips: Enter curve length, driver eye height (default 0.75m), positive grade angle (default 0.785 rad), obstruction height (default 0.36m), and negative grade angle (default -45%). All values must be valid (no division by zero).

5. Frequently Asked Questions (FAQ)

Q1: Why is the negative grade angle in percentage?
A: Negative grade is typically expressed as percentage in road design (e.g., -5% grade).

Q2: What's a typical driver eye height?
A: Standard is 0.75m (2.5 ft) for passenger vehicles, but may be higher for trucks.

Q3: How is obstruction height determined?
A: Typically 0.36m (1.2 ft) representing taillight height of preceding vehicle.

Q4: What's the practical range for positive grade angle?
A: Usually between 0.1 to 1.0 radians (about 5.7° to 57.3°).

Q5: When would this calculation be most critical?
A: For crest vertical curves where visibility is most limited.

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