1. What is Sight Distance when S is Less than L?

Definition: This calculator determines the minimum sight distance required when the stopping sight distance (S) is less than the length of the vertical curve (L).

Purpose: It helps transportation engineers ensure safe visibility conditions on roads, particularly on vertical curves.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Sight Distance (meters)
• \( c \) — Tangential Correction (dimensionless)
• \( H \) — Height of Observer's Eye (meters)
• \( h \) — Height of Object (meters)

Explanation: The formula calculates the minimum distance required for a driver to see an object on the road, considering the heights of both the observer and the object.

3. Importance of Sight Distance Calculation

Details: Proper sight distance ensures safe stopping conditions, prevents accidents, and is a critical factor in road design standards.

4. Using the Calculator

Tips:

• Enter the tangential correction (typically 0.5 ±5%)
• Standard height for driver's eye (H): 1.2 meters
• Standard height for object (h): 2.0 meters (for vehicles)
• All values must be positive numbers

5. Frequently Asked Questions (FAQ)

Q1: What is tangential correction (c)?
A: It's a factor that accounts for the elevation difference between the curve and the tangent to it, typically around 0.5 with ±5% variation.

Q2: When is this formula applicable?
A: When the required sight distance (S) is less than the length of the vertical curve (L).

Q3: What are standard height values?
A: For cars, H=1.2m (eye height) and h=0.15m (object height). For trucks, H=2.4m and h=0.6m.

Q4: How does sight distance affect road design?
A: It determines minimum curve lengths, crest vertical curves, and stopping distances for safe driving.

Q5: What if S is greater than L?
A: A different formula is used when sight distance exceeds the vertical curve length.

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