ERA 2013 Junction & Roundabout Geometry Checker
Evaluate roundabout Inscribed Circle Diameter (ICD), entry deflection radius (R_e), circulatory roadway width, truck apron sizing, design vehicle swept paths, and corner sight triangles (S_tri) strictly per ERA 2013 guidelines.
ERA 2013 DESIGN EVALUATION REPORT
AT-GRADE INTERSECTION GEOMETRIC DESIGN EVALUATION REPORT
Calculated per ERA 2013 Guidelines & Standard Specifications
Date: 8/10/2026
Engineer: [Insert Engineer Name]
Project: [Insert Project Title]
Section: [Insert Section Details]
Intersection Type: Single-Lane Roundabout
Design Vehicle: DV3 / WB-15 (Semi-Trailer Combination)
Design Standard Manual Option
Geometric Layout & Swept Path Diagram
Single-Lane Roundabout (DV3)ERA 2013 Compliance Verification Checklist
| Parameter | Actual Value | ERA 2013 Requirement | Status |
|---|---|---|---|
| Inscribed Circle Diameter (ICD) Compliant roundabout footprint. | 36 m | 28 - 45 m | pass |
| Entry Radius (R_e) Good deflection radius. | 20 m | 15 - 25 m | pass |
| Circulatory Roadway Width (W_circ) Adequate clearance provided. | 7 m | ≥ 6 m | pass |
| Central Island Truck Apron Sufficient mounting apron. | 2 m | 1.5 - 3.0 m | pass |
| Unobstructed Corner Sight Distance (S_tri) Keep sight triangle clear of walls, dense trees, or structures for 125m along major corridor. | 125 m | ≥ 125 m | pass |
Intersection Civil Material Takeoff
- Design Vehicle selected: DV3 / WB-15 (Semi-Trailer Combination) (17m length). Ensure swept path templates are checked in CAD per ERA 2013.
- Maintain minimum 2.0% crossfall outwards on circulatory roadways for drainage per ERA 2013 standards.
1. Geometric Evaluation Summary
Overall Compliance Status: PASS
Design Speed: Major Road 60 km/h | Minor Road 40 km/h
Unobstructed Corner Sight Distance (S_tri): 125 meters
2. Detailed Parameter Checklist
| Parameter | Actual | ERA Limit | Status |
|---|---|---|---|
| Inscribed Circle Diameter (ICD) | 36 m | 28 - 45 m | PASS |
| Entry Radius (R_e) | 20 m | 15 - 25 m | PASS |
| Circulatory Roadway Width (W_circ) | 7 m | ≥ 6 m | PASS |
| Central Island Truck Apron | 2 m | 1.5 - 3.0 m | PASS |
| Unobstructed Corner Sight Distance (S_tri) | 125 m | ≥ 125 m | PASS |
3. Quantity Takeoff Estimate
| Item Description | Unit | Quantity |
|---|---|---|
| Island & Truck Apron Concrete Paving | m² | 380 |
| Asphalt Concrete Surfacing (Circulatory / Taper Area) | m² | 638 |
| Precast Pre-painted Kerbstones (Mountable / Barrier) | m | 119 |
Junction & Roundabout Geometry Checker Documentation
Technical specifications, mathematical formulas, and civil guidelines
1. Functional Purpose
The **Junction & Roundabout Geometry Checker** provides automated verification of at-grade intersection dimensions in strict compliance with **ERA Geometric Design Manual 2013 (Chapter 9)** and **Junction Standard Drawings**.
It checks Inscribed Circle Diameter (ICD), entry radius (R_e) deflection, circulatory roadway width, central island truck apron dimensions, design vehicle swept paths (DV1 to DV4/WB-15), and corner sight triangles (S_tri) to prevent truck grounding and collision hazards.
2. Governing Formulas
Unobstructed Corner Sight Distance (S_tri) along the major road is calculated per ERA Equation 9.1:
Where t_gap = 7.5s for heavy trucks (DV2/DV3/DV4) and 6.5s for passenger cars (DV1). Entry speed V_entry is restricted by entry curvature: V_entry = √(127 × R_e × (e + f)).