In this article, we explained the what is camber in road, why camber is provided in roads, its importance, types of camber and its requirement in various types of pavement. Also shown the recommended values of camber of road as per IRC, camber formula, etc.
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Table of Contents
What is Camber in Road
Camber is a slope provided on the road surface in the transverse direction to drain out the rain water from surface to avoid skid of vehicles and pavement damages.
Camber is again one of the most important element of a road pavement which have lot’s of advantages for longer durability of road surface.
Generally, A camber is a crown shape element on the surface which is created by a elevating the center of carriageway with respect to its edges.
The rate of camber or cross slope of road is usually designated by 1 in ‘n’ which means that the transverse slope is in ratio 1 vertical to n horizontal or it can be expressed in term of percentage. For example 2.5% camber means the camber of road is 1 in 40.
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Importance of Camber on Road
The camber is very important for following points.
- Subbase Stability
- Stripping of Bitumen Layers
- To Avoid Skid of Vehicles
1. Subbase Stability
To prevent the entry of water into the road pavement layers and subgrade base; If surface water enters into a subgrade through pavement causes a heavy damage on road. Because water soaked by soil and it may be get settled, which leads the heavy damages on the road surface.
2. Stripping of Bitumen layers
To Avoid the entry of water into the bituminous surface of pavement; Continue contact of water with bituminous surface leads the loosening of aggregate particles and causes deterioration of the pavement layer.
3. To Avoid Skid of Vehicles
The skid resistance of the pavement decreases if the pavement surface is wet which leads the unsafe condition for vehicles driving. That’s why it is necessary to remove water from pavement surface as soon as possible which can be done by a proper camber.
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Requirement of Camber
The requirement of camber is depend on the type of pavement and rainfall amount.
- The Flat camber can be sufficient on impervious pavement such as concrete or bituminous pavement.
- The Steeper camber is required in a surface which allows water to enters into the pavement layers such as water bond macadam, earthen road, etc.
- Also, Steeper camber is required where the intensity of rainwater is high.
Again, The steeper means not too steep, Too Steep cross slope of roads causes the uncomfortable side thrust and drag on steering wheels, problems during vehicle overtaking, formation of cross ruts, etc.
Recommended Values of Camber in Road
The value of camber recommended by IRC is mentioned in below table .
|Type of Road Surface
|Heavy Rain Fall
|Low Rain Fall
|Cement Concrete and High type bituminous surface
|1 in 50 or 2.0%
|1 in 60 or 1.0%
|Thin Bituminous surface
|1 in 40 or 2.5%
|1 in 50 or 2.0%
|Water Bound Macadam and gravel pavement
|1 in 33 or 3.0%
|1 in 40 or 2.5%
|1 in 25 or 4.0%
|1 in 33 or 3.0%
The camber of road is subjected to minimum 3.0% and maximum 5.0% for earth shoulder.
The camber is suggested for paved surface and edge strip of expressways with bituminous surface as well as concrete surface is 2.5% where annual average rainfall is more than 1000mm. And 2.0%in a regions where annual average rainfall is less than 1000mm.
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Shape of Camber in Road
Generally, In most of the cases, camber is provided in parabolic shape. But it also have different types based on its shape such as a straight line camber and a straight line with parabolic shape camber.
The shape of camber is adopted as per types of pavement and rainfall intensity. For Cement Concrete Pavement, Straight line camber is usually adopted due to easier in construction.
How to find a Height of camber in road example
i) For example, A 6m wide two lane highway with cement concrete surface. What should be the height of the camber with respect to the edges?
In Cement Concrete surface, Mostly Straight line camber was used. And assuming the heavy rainfall region.
As per recommended value of camber by IRC, for cement concrete pavement in heavy rainfall region, a 2.0% camber is adopted.
2.0% camber means 1 in 50.
Therefor the height of camber is = (6/2) x (1/50) = 0.06m
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ii) For example, find the height of camber in road of 3.8m wide water bond macadam pavement in heavy rain fall area.
For Bituminous and WBM Pavement, Mostly a parabolic camber was used on road surface.
As per recommended value of camber by IRC, for Water Bond Macadam Pavement in heavy rainfall region, a 3.0% camber is adopted.
3.0% camber means 1 in 33
Therefore, the height of camber is find by given below formula at X meter distance in parabolic shape.
Camber height in parabolic shape at X Meter distance (Y) = (2X^2)/(nW)
- Y = Height of camber at X meter distance
- X = Horizontal Distance
- n = 33 ( 1 in n)
- W = Width of pavement
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