ERA 2013 Highway Design Standards: A Guide to Ethiopian Road Classes and Geometric Constraints

Road design in Ethiopia is governed by the **ERA Highway Design Manual 2013**. This manual defines design speed thresholds, minimum horizontal radii, maximum gradients, and safety clearances based on functional classes and terrain categories.

Understanding these specifications is key to ensuring that geometric designs comply with local road standards.

1. ERA Road Classes (DS1 to DS10)

Roads are classified from DS1 (trunk roads with high traffic) to DS10 (rural roads with low traffic volume):

2. Geometric Speed Checker Code

This JavaScript code checks whether a design radius complies with the minimum requirement for the specified road class:

function checkMinRadius(roadClass, designSpeed, radius) {
  // Standard ERA minimum radius lookup table
  const minRadii = {
    "DS1": { 120: 650, 100: 450, 80: 250 },
    "DS3": { 100: 395, 80: 230, 50: 85 },
    "DS5": { 85: 270, 70: 175, 40: 50 }
  };
  
  const classLimits = minRadii[roadClass];
  if (!classLimits) return { pass: true, msg: "Class standard not constrained." };
  
  const minRequired = classLimits[designSpeed];
  if (!minRequired) return { pass: true, msg: "Speed standard not constrained." };
  
  return {
    pass: radius >= minRequired,
    required: minRequired,
    msg: radius >= minRequired ? "Valid Radius" : "Warning: Falls below minimum required radius!"
  };
}

Integrating these standard lookup tables helps check for design compliance during the planning stages.