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The road studs are retro-reflective supplements used in the road to improve visibility at night time and adverse weather conditions. Road studs serve the purpose of speed arrestor before junction/crossings/end of the flyover section wherein road crashes are prevalent.

Fig 1: Different types of road studs.

In this article, we discuss the types, requirement, placement, and spacing of road studs on different types of roads.

Types of Road Studs

The classification of road studs based on the basis of colors is as follows :

1. White Color

The white colored road studs indicate the traffic lane line and centre of carriageway.

2. Red Color

As the color red indicates danger, the red-colored road studs are to be used to indicate a line that should not be crossed and mainly to delineate the left-hand edge of the running carriageway.

3. Yellow Color

The yellow color road studs are deployed to indicate a line that should not be crossed with the aim to delineate the right-hand edge of the running carriageway in case of the multi­-lane divided carriageways.

4. Green Colour

Green road studs are to be employed to indicate crossable edge line like the lay byes and to how the boundary of acceleration or deceleration line on left-hand side of the carriageway in case of the multi-lane divided carriageways.

Other Types

Based on the number of reflective sides, abrasion resistance and flexural strength the road studs are divided as follows-

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  1. Type A – Two-way reflective markers, one color.
  2. Type B – One-way reflective markers, one color.
  3. Type D – Two-way reflective markers, two colors.
  4. Designated H – Stud with a hard, abrasion-resistant lens surface.
  5. Designated F – Stud with sufficient longitudinal strength for application to flexible, asphaltic concrete pavement.

Standard Requirement of Road Studs

The standard requirements of road studs are divided in the 3 categories-

1. Construction Requirement

  1. The road stud shall be manufactured of materials with adequate chemical, water, and UV resistance.
  2. The height and width of the road stud shall not exceed 20.3 mm (0.80 in.) and 130 mm (5.1 in.) respectively.
  3. The angle between the face of the road stud and the base shall be no greater than 45°.
  4. The base of the road stud shall be flat within 1.3 mm (0.05 in.).
  5. The base of the road stud shall be substantially free from gloss or substances that may reduce its bond to adhesive.

2. Performance Requirement

  1. The coefficient of luminous intensity of road studs shall be not less than the values mentioned in the table below.
  2. The adhesive bond used for the installation of the road stud must be of superior quality and the failure of road studs sue to adhesive strength must be 1.5 times lesser than the failure of road studs.

Table 1: Required Coefficient of Luminous Intensity of Road Studs

3. Physical Requirement

  1. Flexural Strength The flexural test is carried out for the designated F road Markers withstand 909 kg (2000 lb) without breakage.
  2. Compressive Strength – The road stud shall support a load of 2727 kg (6000 lb) without breakage or significant deformation (3.3 mm) of the road stud.
  3. Lens Impact Strength – When impacted the face of the lens shall show no more than two radial cracks longer than 6.4 mm (0.25 in.).
  4. Temperature Cycling – When subjected to temperature cycling there shall be no cracking or delamination.

Placement of Road Studs

  1. The road studs installed on the longitudinal markings shall always be placed at the center of the gap and shall never be installed upon the line segment or by the side of the line segment.
  2. In the case of the road studs placed on the carriageway having a paved shoulder, it shall be placed outside the shoulder side edge line and shall have a set back by a distance of 50 mm from the edge line.
  3. For the road studs provided on the median side are to be ensured that it shall not be on the median line marking, but shall be in the hard strip or kerb shyness width with a set back of 50mm from the median and 100 mm from the vertical face of the raised kerb.
  4. In extreme circumstances, if the width of hard strip or shyness is not adequate enough to accommodate the required set back distance of 50 mm from the edge line, the road studs can be placed adjacent to the edge line and even directly on the edge lines.

Details of Placement, Color, and Spacing of Road Studs on Divided and Un-Divided Roads

1. Road Studs for Undivided Roads

Table 2: Details of placement, color, and spacing of road studs on undivided roads

Undivided Road
Undivided Road
Fig 2: Pictorial representation of placement and color of road studs in undivided roads.

2. Road Studs for Divided Roads

Table 2: Details of placement, color, and spacing of road studs on divided roads

Divided Road
Divided Road
Fig 3: Pictorial representation of placement and color of road studs in divided roads.

Read More: 7 Types of Road Markings as per IRC-35

Fasi Ur Rahman

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