Stopping & Passing Sight Distance Calculator
Determine required Stopping Sight Distance (SSD), Passing Sight Distance (PSD), vertical curve K-values (Crest & Sag), and horizontal curve obstruction setback clearances (m_s) per ERA 2013 standards.
Report Metadata
Design Standard Manual Option
Geometric Design Parameters
Distance & Sight Line Component Breakdown
Vertical Curve Minimum K-Values (K = L / A)
m_s = 9.64 meters (Clearance from centerline to obstruction on R = 300m curve)
STOPPING & PASSING SIGHT DISTANCE CALCULATION REPORT
Strictly Formatted per ERA Geometric Design Manual 2013 Specifications
| Project Name: | [Insert Project Title] | Date / Time: | 8/10/2026 |
| Section / Location: | [Insert Section Details] | Design Standard: | ERA Geometric Manual 2013 |
| Highway Engineer: | [Insert Engineer Name] | Design Speed: | 80 km/h |
1. Sight Distance & Component Breakdown
| Grade (%) | Perception Dist | Braking Dist | Specified SSD | ERA Min PSD |
|---|---|---|---|---|
| -4% | 55.6 m | 96.91 m | 152.51 m | 560 m |
2. Curve K-Values & Lateral Setback Clearance
| Crest Vertical K | Sag Vertical K | Curve Radius (R) | Lateral Setback (m_s) |
|---|---|---|---|
| K = 35.3 | K = 35.6 | 300 m | 9.64 m |
I hereby certify that the sight distance calculations and vertical/horizontal parameters reported herein comply strictly with the Ethiopian Roads Administration (ERA) Geometric Design Manual 2013.
Engineering Guidance & Concept Notes (ERA 2013 Manual)
1. Downgrade Corrections
Steep downgrades significantly increase braking distance due to gravitational acceleration. ERA mandates adding up to 35% extra SSD on -6% to -10% downgrades.
2. K-Value Design
Crest vertical curve length L = K · A must satisfy driver eye height h1 = 1.07m and object height h2 = 0.15m to ensure unobstructed line of sight.
3. Obstruction Setback
Ensure trees, cut slopes, and sound walls on the inside of horizontal curves are set back at least m_s meters from the inner lane centerline.
Stopping & Passing Sight Distance Calculator Documentation
Technical specifications, mathematical formulas, and civil guidelines
1. Functional Purpose
The Stopping & Passing Sight Distance Calculator determines required sight line distances, vertical curve minimum K-values, and horizontal curve obstruction setback clearances (m_s) according to the ERA Geometric Design Manual 2013.
It ensures drivers have adequate reaction time and braking distance on upgrades/downgrades, determines minimum Crest and Sag vertical curve lengths (K = L / A), and exports a professional dark-lined calculation report formatted for official printing and submission.
2. Practical Workflow Instructions
- Select Design Speed (V): Choose the project design speed from 30 km/h to 120 km/h.
- Input Longitudinal Grade (G%): Specify road gradient (+ for upgrades, - for downgrades).
- Adjust Reaction Time & Curve Radius: Set driver perception-reaction time (t = 2.5s default) and optional horizontal curve centerline radius (R in meters).
- Print / Export Report: Click Print Clean Report to export a black-bordered professional calculation sheet formatted for PDF printing.
3. Mathematical & ERA Standard Formulas
Stopping Sight Distance (SSD) is computed using:
Crest and Sag vertical curve minimum K-values:
Horizontal curve obstruction setback clearance distance (m_s):