Recommended Practice for Road Delineators (First Revision)

IRC 79 - Introduction: Key Specifications for Roadway Indicators

• Scope: IRC 79 covers specifications for roadway indicators such as median markers, hazard markers, and object markers, focusing on their placement, spacing, installation, and maintenance.

• Horizontal Curve Spacing (Clause 3.11):
  The spacing of roadway indicators on curves depends on the curve radius (R). The normal spacing on the curve is denoted as S.

• Approach Spacing: On approaches to curves, place the first, second, and third delineators at distances of 1.8 S, 3 S, and 6 S respectively, but not exceeding 50 m.

• Installation Notes:

  • Place delineators at the edge of the roadway, perpendicular to oncoming traffic.
  • Adjust the initial distance so the last delineator aligns with the curve end.

flowchart LR
    A[Start of Curve] --> B{Place Delineators}
    B --> C[Spacing = S (on curve)]
    B --> D[Approach Spacing: 1.8S, 3S, 6S]
    C --> E[Adjust 'x' so last delineator at curve end]
    D --> E
    E --> F[Install perpendicular to traffic edge]

This ensures clear guidance for drivers on horizontal curves, enhancing road safety.

IRC 79 - Scope: Key Specifications & Tables

• Scope (Clause 2): IRC 79 covers specifications for roadway indicators including median markers, hazard markers, and object markers, focusing on placement, materials, and maintenance for safe highway delineation.

Key Table: Spacing of Roadway Indicators on Horizontal Curves (Clause 3.11)

• Spacing on Approaches:
  • 1st indicator: 1.8 × S
  • 2nd indicator: 3 × S
  • 3rd indicator: 6 × S
  • Max spacing: 50 m

Material & Dimensional Specifications

• Body Thickness: ≥ 6.5 mm
• Shank Length: ≥ 20 mm; Depth ≥ 30 mm
• Reflective Area: ≥ 90 cm²
• Durability: Bounce back after 750 hits with 1.8 kg pendulum (ASTM D 256)
• Adhesion Strength: ≥ 50 Kgf tensile load (ASTM D 638)

Application Distances for Flexible Median Markers (FMM)

flowchart LR
    A[Horizontal Curve Radius] --> B{Select Spacing S}
    B -->|30m| C[6 m spacing]
    B -->|50m| D[8 m spacing]
    B -->|100m| E[12 m spacing]
    B -->|200m| F[20 m spacing]
    B -->|300m| G[25 m spacing]
    H[Approach Spacing] --> I[1.8 S, 3 S, 6 S]
    I --> J[Max 50 m]

This summary ensures proper placement and material standards for highway delineators per IRC 79.

IRC 79: Roadway Indicators – Key Points

When to Use Roadway Indicators (Clause 3.7)

• Curved Sections:
  • Horizontal curves with radius ≤ 300 m
  • Vertical curves with poor visibility
• Straight Sections:
  • Poor visibility zones (fog, mist, snow)
  • Ambiguous alignment (pavement width changes, diversions)
  • Areas prone to submergence/ponding
  • Near narrow bridges/culverts
  • Valley sides of hill roads
  • Embankments > 3 m high
  • Approaches to important intersections
  • Special points: causeways, tunnels

Placement & Spacing (Clause 2.3)

• Roadway indicators (delineators) are aids to driving, not substitutes for signs or barriers.
• Install at regular intervals to guide drivers, especially in low visibility or complex alignments.

Summary Table: Typical Use Cases for Roadway Indicators

Conceptual Diagram of Roadway Indicator Placement

graph LR
A[Start of Curve] --> B[Place Indicator]
B --> C[Every 20-30 m on curves]
C --> D[End of Curve]
E[Straight Road with Poor Visibility] --> F[Place Indicator]
F --> G[Every 50 m on straight sections]

Note: Refer IRC 79 full text for detailed spacing, reflector types, and installation heights.

IRC 79 – Median Marker Key Specifications & Formulas

1. Flexible Median Marker (FMM) Specifications

• Material: Tough, high impact resistant, flexible thermoplastic (injection molded).
• Colour: Body - Neutral Black; Retroreflective sheeting - Fluorescent Yellow (Type XI as per IRC:67).
• Height: Minimum 180 mm.
• Width: Minimum 120 mm.
• Reflective Sheeting: On both faces for max visibility.
• Durability:
  • Bounce-back after 750 hits with 1.8 kg pendulum (ASTM D 256).
  • Adhesion withstands 50 Kgf tensile load (ASTM D 638).

2. Installation & Spacing

• Fixed by epoxy adhesive + grouting/drilling on concrete/solid medians.
• Spacing:
  • Urban areas: 2 m
  • Interurban highways/expressways: 5 m
  • Problematic locations (e.g., causeways): 5 or 10 m (as per local conditions).

3. Purpose

• Enhances median visibility during night/severe weather.
• Prevents collisions with medians.

Typical Dimensions Summary

flowchart LR
    A[Median Marker] --> B[Flexible Thermoplastic Body]
    A --> C[Fluorescent Yellow Retroreflective Sheeting (Type XI)]
    A --> D[Height ≥ 180 mm]
    A --> E[Width ≥ 120 mm]
    A --> F[Installed every 2-5 m depending on location]
    F --> G[Urban: 2 m]
    F --> H[Highways: 5 m]
    F --> I[Problematic Areas: 5-10 m]

This ensures high durability, visibility, and safety for medians on Indian roads as per IRC 79.

IRC 79: Hazard Markers Key Specifications

• Design: Alternating black & yellow stripes at 45° slope, slanting downward toward the side traffic should pass.
• Material: Use Type XI retroreflective sheeting as per IRC:67 for visibility.
• Dimensions (Fig. 9 reference):
  • Each stripe approx. 200 mm wide
  • Marker height approx. 225 mm
• Types:
  • Left Hazard Marker (Fig. 9a)
  • Right Hazard Marker (Fig. 9b)
  • Two-way Hazard Marker (Fig. 9c)
• Application: Place on fixed roadside obstructions like bridge abutments, guard rails, narrow bridges (Fig. 10).
• Placement: Markers must be clearly visible day & night, installed at edges of hazards on the traveled way.

Summary Table of Hazard Marker Dimensions

Illustration of Stripe Orientation

flowchart LR
    A[Top of Marker]
    B[Black Stripe]
    C[Yellow Stripe]
    D[Traffic Passes Here]
    A --> B --> C --> B --> C
    B -. 45° slope .-> D

Note: Stripes slope downward at 45° toward the safe passage side.

This ensures maximum visibility and clear guidance to drivers approaching roadside hazards per IRC 79.

IRC 79 - Object Markers: Key Specifications and Formulas

1. Design & Appearance (Clause 5.1 & 6)

• Object Hazard Markers (OHM) use alternating black and yellow stripes sloping downward at 45° towards the safe side.
• Markers must use Type XI reflective sheeting as per IRC:67.
• Shapes: Rectangular or circular aluminum-backed flexible prismatic reflective sheeting.

2. Dimensions (Clause 6.3)

• Width: 300 mm (fixed)
• Length: Minimum 400 to 500 mm (varies by site)
• Reflectors must be fully visible to approaching traffic.

3. Placement (Clause 5.3 & 6)

• Place on objects at the edge of the travelled way (e.g., bridge abutments, guard rails).
• For channelizing islands/roundabouts, place only on the nose facing traffic, not the entire periphery.
• On narrow bridges, markers continue curves to guide traffic (Fig. 10).

4. Installation

• Markers slope downward at 45° towards the side traffic should pass.
• Use reflective sheeting for night visibility.

Summary Table

flowchart LR
    A[Object on Road Edge] --> B[Apply Object Marker]
    B --> C{Marker Shape}
    C --> D[Rectangular]
    C --> E[Circular]
    B --> F[Reflective Sheeting Type XI]
    B --> G[Stripe Angle 45° Downward]
    B --> H[Width 300mm, Length 400-500mm]
    B --> I[Placement on Nose, Facing Traffic]

This ensures enhanced nighttime visibility and traffic safety with minimal investment.

IRC 79: Installation of Roadway Delineators & Markers

Key Specifications (Clause 7.1)

• Foundation: Use M-25 grade concrete for all delineator installations.
• Orientation: Ensure posts (especially circular) maintain orientation and do not rotate.
• Ground Conditions: Installation techniques vary with ground stiffness and local customs.

Spacing on Horizontal Curves (Clause 3.11 & Table 1)

• Approach Spacing:
  • 1st delineator: 1.8 × S
  • 2nd delineator: 3 × S
  • 3rd delineator: 6 × S
  • Max spacing = 50 m
• Install delineators perpendicular to traffic at edge of roadway.

Object Marker Dimensions (Clause 6.3)

• Width: 300 mm
• Length: 400–500 mm (minimum) to ensure reflector visibility.

Summary Diagram of Spacing on Curves

flowchart LR
    A[Start of Curve] --> B[Place delineator at spacing S]
    B --> C[Place 1st approach delineator at 1.8S]
    C --> D[Place 2nd approach delineator at 3S]
    D --> E[Place 3rd approach delineator at 6S]
    E --> F[Continue delineators along curve at spacing S]

Note: Always adjust spacing so the last delineator aligns with the end of the curve.

IRC 79 - Maintenance Key Points

• Clause 8 (Page 13) covers maintenance of Flexible Median Markers (FMM).

Key Specifications for Maintenance of FMM:

• Impact Resistance:
  The FMM body must return to its original position after 750 hits from a 1.8 kg pendulum (ASTM D 256).

• Adhesion Strength:
  The bond between the FMM body and outer casing must withstand 50 kgf tensile load (ASTM D 638).

Application & Placement for Maintenance:

• Maintain minimum distances for FMM placement:
  • Urban areas: 2 m
  • Interurban highways/expressways: 5 m or as directed by Engineer In-charge.

Spacing on Horizontal Curves (Maintenance of Delineators):

• On curves, place delineators at edge of roadway perpendicular to traffic.
• First 3 delineators before/after curve spaced at 1.8S, 3S, and 6S respectively (max 50 m).

flowchart LR
    A[FMM Impact Test] --> B[750 hits by 1.8kg pendulum]
    B --> C[Body returns to original position]
    A --> D[Adhesion test]
    D --> E[50 kgf tensile load]
    E --> F[Bond intact]
    G[Placement] --> H[Urban: 2m]
    G --> I[Interurban: 5m]
    J[Curve Spacing] --> K[Use Table for S]
    K --> L[Install delineators perpendicular to traffic]

Summary: Regularly check FMM for impact resilience and adhesion, maintain spacing per curve radius, and ensure correct placement distances for visibility and durability.