1. What is Driver Sight Height given Angle Grades?

Definition: This calculator determines the required driver eye height based on vertical curve geometry, sight distance, and grade angles.

Purpose: It helps transportation engineers design roads with adequate visibility for safety, especially on vertical curves.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( h1 \) — Driver sight height (meters)
• \( Ls \) — Length of vertical curve (meters)
• \( S \) — Sight distance (meters)
• \( n1 \) — Positive grade (decimal)
• \( h2 \) — Height of obstruction (meters)
• \( n2 \) — Negative grade (decimal)

Explanation: The formula accounts for the curve geometry, sight distance requirements, and the relationship between upward and downward slopes.

3. Importance of Driver Sight Height Calculation

Details: Proper sight height calculation ensures drivers can see obstacles or other vehicles in time to react safely, especially on hilly terrain.

4. Using the Calculator

Tips: Enter all required values in meters for lengths and percentages for grades. Negative grade should be entered as a negative percentage (e.g., -5%).

5. Frequently Asked Questions (FAQ)

Q1: What's a typical driver eye height?
A: Standard design uses 1.08m (3.5ft) for passenger cars and 2.33m (7.6ft) for trucks.

Q2: Why are grades entered as percentages?
A: Grade is typically expressed as percentage in transportation engineering (e.g., 5% grade rises 5m per 100m).

Q3: What if my negative grade is positive?
A: The formula requires the negative grade to be negative (downward slope). Enter as a negative percentage.

Q4: What's the minimum sight distance required?
A: This varies by road speed. For example, 60mph (97km/h) typically requires 183m (600ft) stopping sight distance.

Q5: How does curve length affect sight height?
A: Longer curves generally require higher driver eye positions to maintain the same sight distance over the crest.

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