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), with equal object and eye heights.

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

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( SD \) — Sight Distance (meters)
• \( h \) — Height of driver's eye/object (meters)
• \( L_c \) — Length of vertical curve (meters)
• \( g1 \) — Upgrade gradient (%)
• \( g2 \) — Downgrade gradient (%)

Explanation: The formula calculates the minimum distance required for a driver to see an object on the road when approaching a vertical curve.

3. Importance of Sight Distance Calculation

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

4. Using the Calculator

Tips: Enter the height of vertical curves, length of curve, upgrade percentage, and downgrade percentage. Note that downgrade should be entered as a negative value.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical height used for calculations?
A: Standard values are 1.08 meters (3.5 ft) for driver's eye height and 0.60 meters (2.0 ft) for object height.

Q2: How are upgrade and downgrade represented?
A: Upgrade is positive (e.g., +5%) and downgrade is negative (e.g., -3%). The calculator handles the sign automatically.

Q3: When is this formula applicable?
A: This formula is used when the stopping sight distance (S) is less than the length of the vertical curve (L).

Q4: What if S is greater than L?
A: A different formula is used when sight distance exceeds the curve length.

Q5: What safety factors should be considered?
A: Always include a safety margin and consider factors like reaction time, vehicle speed, and road conditions.

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