Recommended Practice for Road Delineators (First Revision)
2019 Edition

IRC 79 - Overview: Essential Guidelines for Roadway Delineation Devices

• Scope: IRC 79 specifies requirements for roadway delineators such as median, hazard, and object markers, detailing their positioning, spacing, installation, and upkeep.

• Spacing on Horizontal Curves (Clause 3.11):
  The interval between delineators on curves is based on the curve radius (R), with the typical spacing denoted as S.

• Approach Placement: The first, second, and third delineators before curves should be placed at distances of 1.8 S, 3 S, and 6 S respectively, with a maximum spacing of 50 m.

• Installation Notes:

  • Position delineators at the roadway edge, aligned perpendicular to oncoming traffic.
  • Adjust initial placement so the last delineator coincides with the curve’s end.

flowchart LR
    A[Curve Start] --> B{Install Delineators}
    B --> C[Spacing = S (along curve)]
    B --> D[Approach Distances: 1.8S, 3S, 6S]
    C --> E[Adjust initial offset for last delineator]
    D --> E
    E --> F[Mount perpendicular to traffic at road edge]

This arrangement provides drivers with clear visual cues on curves, promoting safer navigation.

IRC 79 - Scope and Technical Requirements

• Scope (Clause 2): Encompasses standards for roadway delineators including median, hazard, and object markers, emphasizing placement, materials, and maintenance to ensure highway safety.

Important Table: Delineator Spacing on Horizontal Curves (Clause 3.11)

• Approach Distances:
  • 1st delineator: 1.8 × S
  • 2nd delineator: 3 × S
  • 3rd delineator: 6 × S
  • Maximum gap: 50 m

Material and Dimension Standards

• Minimum Body Thickness: 6.5 mm
• Shank Length: At least 20 mm, with embedment depth ≥ 30 mm
• Reflective Surface Area: Minimum 90 cm²
• Impact Resistance: Must withstand 750 impacts from a 1.8 kg pendulum (ASTM D 256)
• Adhesion Strength: Minimum 50 kgf tensile load (ASTM D 638)

Minimum Distances for Flexible Median Markers (FMM)

| Location Type | Minimum Distance from Median (m) |\n|--------------------|----------------------------------| | Urban Areas | 2 | | Interurban/Expressways | 5 |

flowchart LR
    A[Curve Radius Input] --> 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 Delineators] --> I[1.8S, 3S, 6S Distances]
    I --> J[Max Spacing 50 m]

This section ensures correct placement and material quality for highway delineators as per IRC 79.

IRC 79: Essential Details on Roadway Delineators

Recommended Use (Clause 3.7)

• Curved Road Segments:
  • Horizontal curves with radius ≤ 300 m
  • Vertical curves with limited sight distance
• Straight Road Segments:
  • Areas with poor visibility due to weather conditions (fog, mist, snowfall)
  • Locations with unclear alignment, such as lane width transitions or detours
  • Spots prone to flooding or waterlogging
  • Near narrow bridges or culverts
  • Valley-facing slopes on hill roads
  • Embankments over 3 m in height
  • Approaches to significant intersections
  • Special locations like causeways and tunnels

Placement and Interval (Clause 2.3)

• Delineators serve as navigational aids and do not replace traffic signs or barriers.
• Install at consistent intervals to assist drivers, especially in challenging visibility or complex alignment zones.

Usage Summary Table

Conceptual Placement Diagram

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

Note: Refer to the full IRC 79 document for detailed spacing, reflector types, and mounting heights.

IRC 79 – Median Marker Specifications and Installation Guidelines

1. Flexible Median Marker (FMM) Characteristics

• Material: Durable, impact-resistant flexible thermoplastic formed by injection molding.
• Color Scheme: Neutral black body with fluorescent yellow retroreflective sheeting on both sides (Type XI as per IRC:67).
• Dimensions: Minimum height of 180 mm and width of 120 mm.
• Reflective Sheeting: Applied on both faces to maximize visibility.
• Durability:
  • Must endure 750 impacts from a 1.8 kg pendulum without permanent deformation (ASTM D 256).
  • Adhesion strength between body and casing must resist 50 kgf tensile force (ASTM D 638).

2. Installation and Spacing

• Affixed to concrete or solid medians using epoxy adhesive with grouting or drilled anchors.
• Recommended spacing:
  • Urban roads: 2 meters
  • Interurban highways/expressways: 5 meters
  • Special situations like causeways: 5 or 10 meters depending on conditions

3. Purpose

• Improves median visibility in night-time and adverse weather.
• Helps prevent vehicle collisions with medians.

Dimension Summary Table

flowchart LR
    A[Median Marker] --> B[Flexible Thermoplastic Material]
    A --> C[Fluorescent Yellow Type XI Reflective Sheeting]
    A --> D[Height ≥ 180 mm]
    A --> E[Width ≥ 120 mm]
    A --> F[Spacing varies between 2-5 m based on location]
    F --> G[Urban: 2 m]
    F --> H[Highways: 5 m]
    F --> I[Special Areas: 5-10 m]

This ensures median markers provide enduring visibility and safety in compliance with IRC 79.

IRC 79: Specifications for Hazard Markers

• Design: Markers feature alternating black and yellow stripes inclined at a 45° angle, sloping downwards towards the side where traffic passes.
• Materials: Use Type XI retroreflective sheeting conforming to IRC:67 for enhanced visibility.
• Dimensions: Approximately 200 mm stripe width and 225 mm overall marker height (refer to Fig. 9).
• Variants: Left hazard, right hazard, and two-way hazard markers (Fig. 9a-c).
• Application: Installed on permanent roadside hazards such as bridge abutments, guardrails, and narrow bridges (Fig. 10).
• Placement: Markers must be clearly visible during day and night and positioned at hazard edges adjacent to the traveled way.

Dimension Summary Table

Stripe Orientation Diagram

flowchart LR
    A[Marker Top] --> B[Black Stripe]
    B --> C[Yellow Stripe]
    C --> B
    B -.-> D[45° slope towards traffic side]

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

This design ensures maximum hazard visibility and clear driver guidance in line with IRC 79.

IRC 79 - Object Marker Specifications and Placement

1. Design and Features (Clauses 5.1 & 6)

• Object Hazard Markers (OHM) have alternating black and yellow stripes inclined downward at 45° towards the side safe for traffic flow.
• Use Type XI reflective sheeting as per IRC:67.
• Shapes include rectangular or circular aluminum-backed flexible prismatic reflectors.

2. Dimensions (Clause 6.3)

• Fixed width: 300 mm
• Length varies between 400 and 500 mm minimum depending on location
• Reflectors must be clearly visible to oncoming vehicles.

3. Placement (Clauses 5.3 & 6)

• Positioned at the edge of the traveled way on objects such as bridge abutments, guardrails.
• For channelizing islands and roundabouts, markers are placed only on the nose facing traffic.
• On narrow bridges, markers follow the curve to guide drivers (Fig. 10).

4. Installation

• Markers are sloped downward at 45° toward the safe side for traffic.
• Equipped with reflective sheeting to ensure night visibility.

Specification Table

flowchart LR
    A[Roadside Object] --> B[Attach Object Marker]
    B --> C{Marker Shape}
    C --> D[Rectangular]
    C --> E[Circular]
    B --> F[Type XI Reflective Sheeting]
    B --> G[45° Downward Stripe Angle]
    B --> H[Dimensions 300x400-500 mm]
    B --> I[Placement on Nose Facing Traffic]

This setup ensures improved nighttime visibility and traffic safety with cost-effective measures.

IRC 79: Guidelines for Installing Roadway Delineators and Markers

Core Requirements (Clause 7.1)

• Foundation: Employ M-25 grade concrete footing for all delineator posts.
• Orientation: Ensure posts, particularly circular types, remain correctly oriented and do not rotate post-installation.
• Ground Conditions: Installation methods should adapt to local soil stiffness and customary practices.

Spacing on Horizontal Curves (Clause 3.11 & Table 1)

• Approach Spacing:
  • 1st delineator at 1.8 × S
  • 2nd at 3 × S
  • 3rd at 6 × S
  • Maximum spacing capped at 50 m
• Install posts perpendicular to the traffic flow at the roadway edge.

Object Marker Dimensions (Clause 6.3)

• Width: 300 mm
• Length: 400–500 mm minimum to guarantee reflector visibility.

Spacing Diagram on Curves

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

Note: Adjust spacing so the final delineator aligns exactly with the curve end.

IRC 79 - Maintenance Guidelines

• Clause 8 outlines maintenance for Flexible Median Markers (FMM).

FMM Maintenance Criteria:

• Impact Resistance: The flexible body must recover after 750 impacts from a 1.8 kg pendulum (ASTM D 256).
• Adhesion Strength: The bond between marker body and outer casing must resist a tensile load of 50 kgf (ASTM D 638).

Placement and Spacing for Maintenance:

• Maintain minimum distances:
  • Urban: 2 meters
  • Interurban/highways: 5 meters or as directed by the Engineer In-charge

Spacing on Horizontal Curves for Delineators:

• Delineators should be positioned perpendicular to traffic at the road edge.
• The first three delineators before and after the curve must be spaced at 1.8S, 3S, and 6S respectively, not exceeding 50 m.

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

Summary: Conduct regular inspections to ensure FMM resilience and adhesion, maintain proper spacing based on curve radius, and verify correct installation distances to preserve visibility and longevity.