Driver Eye Height given Length of Valley Curve Greater than Stopping Sight Distance Calculator

Driver Eye Height Formula:

\[ h1 = \frac{N \times S^2 - 2 \times Ls \times S \times \tan(\alpha)}{2 \times Ls} \]

Deviation Angle (N):

Sight Distance (S):

Length of Curve (Ls):

Inclination Angle (α):

Driver Eye Height (h1): m

1. What is Driver Eye Height Calculation?

Definition: This calculator determines the required driver eye height when the length of a valley curve is greater than the stopping sight distance.

Purpose: It helps transportation engineers ensure proper visibility for drivers on vertical curves in road design.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ h1 = \frac{N \times S^2 - 2 \times Ls \times S \times \tan(\alpha)}{2 \times Ls} \]

Where:

\( h1 \) — Driver eye height (meters)
\( N \) — Deviation angle (percentage)
\( S \) — Sight distance (meters)
\( Ls \) — Length of curve (meters)
\( \alpha \) — Inclination angle (degrees)

Explanation: The formula calculates the minimum eye height needed to maintain visibility along a valley curve.

3. Importance of Driver Eye Height Calculation

Details: Proper eye height calculation ensures safe stopping sight distances are maintained on vertical curves, preventing accidents.

4. Using the Calculator

Tips: Enter the deviation angle (%), sight distance (m), length of curve (m), and inclination angle (°). All values must be > 0.

5. Frequently Asked Questions (FAQ)

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

Q2: Why is deviation angle in percentage?
A: In road design, grade is commonly expressed as a percentage (rise over run × 100).

Q3: When is this calculation most important?
A: For valley (sag) curves where headlight illumination might be insufficient at night.

Q4: How does inclination angle affect the result?
A: Steeper inclinations require higher eye heights to maintain the same sight distance.

Q5: What if my curve length is less than stopping sight distance?
A: A different formula would be used in that case (L ≤ S scenario).