Height of Obstruction Given Angle Grades Calculator

Height of Obstruction Formula:

\[ h_2 = (S - \frac{L_s}{2} - \frac{h_1}{n_1}) \times n_2 \]

Sight Distance (S):

Length of Curve (L_s):

Driver Sight Height (h₁):

Positive Grade Angle (n₁):

Negative Grade Angle (n₂):

Height of Obstruction (h₂): m

1. What is Height of Obstruction Calculator?

Definition: This calculator determines the height of an obstruction based on sight distance, curve length, driver eye height, and road grade angles.

Purpose: It helps transportation engineers and road designers ensure proper visibility and safety by calculating potential obstructions.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ h_2 = (S - \frac{L_s}{2} - \frac{h_1}{n_1}) \times n_2 \]

Where:

\( h_2 \) — Height of the obstruction (meters)
\( S \) — Sight distance (meters)
\( L_s \) — Length of curve (meters)
\( h_1 \) — Driver sight height (meters)
\( n_1 \) — Positive grade angle (%)
\( n_2 \) — Negative grade angle (%)

Explanation: The formula accounts for the geometric relationship between sight distance, vertical curves, and grade changes.

3. Importance of Obstruction Height Calculation

Details: Proper calculation ensures adequate stopping sight distance, prevents visual obstructions, and improves road safety.

4. Using the Calculator

Tips: Enter all required values in meters for distances and height, and percentages for grade angles (± values allowed).

5. Frequently Asked Questions (FAQ)

Q1: What is a typical driver sight height?
A: For passenger cars, 1.08m (3.5ft) is standard. For trucks, use 2.33m (7.6ft).

Q2: How do grade angles affect the calculation?
A: Positive grade is upward slope, negative is downward. The steeper the grade, the greater its impact on obstruction height.

Q3: What if my result is negative?
A: A negative result indicates the sight line clears the obstruction (no height restriction needed).

Q4: How accurate is this calculation?
A: It provides theoretical values. Field verification is recommended for critical applications.

Q5: Does this account for horizontal curves?
A: No, this is for vertical curves only. Horizontal curves require additional considerations.