Table of Contents for Types of Highways-
- Highway Types as per functionality- Types of Highways in India
- Types of highways based on construction material
- Types of highways based on traffic
- Types of highways based on rigidity
- Types of highways based on traffic type
- Types of highways based on topography
- Types of highways based on usage
India has the 2nd largest road network (6.116 million km) while the USA lead the list. In addition, paved roads are 69% of the total Indian road network, and the rest are unpaved. The growth of the Indian road network is evident from the below data.
Road construction is complex. The complexity arises due to terrains, traffic, pavement type, functionality, and cost. Subsequently, it provides room to classify the roads based on different parameters.
In continuation, let us discuss the various types of highways.
Classification as per functionality- Types of Highways in India
There are four types of highways in India- National highways, state highways, district roads and other roads.
An expressway has the best features among all the highway types in India. The higher design speed, wide ROW, controlled entries and exits, etc. It has a minimum of four lanes.
The Ministry of Road Transport & Highways (MoRTH) develops and manages the expressways in India.
It is one of the types of highways in India. It connects major cities and runs throughout the length breadth of the country. All the national highways are constructed and managed by the National Highway Authority of India (NHAI).
As of March 2021, India has 136,440 km long national highways that are roughly 2.4% of the total Indian road network but carries 40% of the traffic. A national highway has a minimum of two lanes.
A state highway runs through the areas and regions of a state and connects to a national highway. It is another type of highway in India having specifications similar to the national highway. The state constructs and manages the state highway. As of December 2020, the state highways had a length of 176,818 km.
One of the highway types in India is district road. It connects the districts of a state and ultimately merges into a national highway or a state highway. Depending upon the traffic and importance, the district roads are of two types – Major District Road and Minor District Road.
A major district road connects the district headquarters and marketplaces. Whereas, a minor district road connects the local areas of a district. It is also called other district roads.
The district authorities are responsible for the construction and management of the district roads.
Village roads connect the villages. The economy is an important factor in the construction of a village road. Therefore, having one or two lanes only. The village council and district council construct and manage the village roads.
The village roads have the largest share in the total road network. However, they carry the least volume of traffic.
Classification of highways based on construction material
A road uses different types of construction materials. Such, as cement concrete, bitumen concrete, murram, earth, WBM, gravel and kankar. The selection of material depends upon the traffic, desired service life, economy and functionality. The types of highways are described in descending order of the cost of construction, i.e., costliest is first, and cheapest is last.
Cement Concrete Road
The cement concrete is the top layer of the cement concrete road. It has a rigid surface. Due to the cement usage, the cost of construction is the highest among all the construction materials. However, the maintenance cost is low. Moreover, the service life is also the highest (typically 25-30 years) among all types of highways.
Check out the field quality control methods for concrete.
The ability of cement concrete roads to handle high traffic is impeccable. Therefore, making it a preferred choice for national highways and state highways. In contrast to the several benefits, cement concrete roads have an inherent drawback of high construction time. It can’t serve traffic during the curing period.
Bitumen Concrete Road
Bitumen concrete is a mixture of bitumen (or asphalt) and coarse aggregate. The bitumen concrete road contains layers of compacted materials. The popularity of bitumen road is due to its’ economy and ability to handle high traffic. The thickness of each layer is dependent on the traffic and the material properties.
The bitumen concrete road life is 15-20 years. However, it needs regular maintenance.
Water Bound Macadam (WBM) roads are low-cost roads. It is a common type of highway in India, especially in rural areas. The road contains layers of coarse and fine aggregate. Each layer is watered and well compacted to offer a motorable surface.
WBM road is cheaper and weaker than a cement concrete road or a bitumen road. Consequently, it carries a lesser traffic load and needs regular maintenance.
Check the soil quality with these site tests for making a road.
Murram is a naturally occurring lateritic material. It finds application in low-cost road construction. Murram road is more stable than an earthen road and requires lesser maintenance.
Kankar is an impure form of limestone. The kankar road is common in rural areas where limestone is abundantly available. It has a low surface finish than other types of roads.
A gravel road uses gravel and soil as a construction material. It is lesser stable than the above-listed roads. You are likely to find a gravel road in rural areas.
The village roads with the least volume of traffic are made of earth. It is the cheapest and simple type of road. To construct an earthen road first, mark the alignment on the ground. Second, level the earth. At last, water the soil and compact the loose pockets.
The cross-profile of an earthen road has higher slopes to drain off the rainwater quickly. The earthen road often becomes non-motorable in heavy rains.
Classification of highways based on traffic
The number of vehicles passing through a highway forms a basis for the classification of highways as per the traffic. Therefore, there are three types of highways as per the traffic- low traffic road, medium traffic road and high traffic road.
Low Traffic Road
A low traffic road carries lesser than 400 vehicles per day. Village roads and minor district roads come under this head. The construction material is bitumen concrete, murram, kankar, WBM, gravel or earth.
Medium Traffic Road
A road carrying 400-1000 vehicles per day is a medium traffic road. The village roads, district roads are often categorised as medium traffic roads.
High Traffic Road
A high traffic road carries more than 1000 vehicles per day. The expressways, national highways, state highways and major district roads are examples of high traffic roads. The construction material used in high traffic roads is cement concrete or bitumen concrete.
Classification of highways based on rigidity
Traffic exerts stress on the road. The load-carrying mechanism of a road depends upon the material used. The road may be flexible or rigid.
As the name suggests, a flexible pavement deflects under the load. The load gets transferred from the top layer to the bottom layer (earth). Subsequently, the failure of the bottom layer reflects through all the overlying layers.
A bitumen concrete road, WBM road, gravel road, kankar road, murram road are examples of flexible roads.
A cement concrete slab evenly distributes the load to the below-lying base course. The property of evenly transferring the traffic load, to the underlying layers is known as flexural rigidity. It is a rigid pavement. The small and local failure of the subgrade doesn’t affect the concrete slab.
The concrete expands and contracts due to temperature variation. Therefore, the rigid pavement has expansion joints at suitable locations.
Classification of highways based on traffic type
Traffic is a common term for pedestrians, bicycles, and vehicles. Each of the traffic components has its’ individual speed of travel. Hence, it becomes necessary to segregate them from each other by providing a separate road. Therefore, reducing the congestion and increasing safety.
Each country has laws about road designs and operations based on traffic type.
A pedestrian track is for the pedestrians. Usually, a sidewalk (or footpath) is provided by the side of the main road. A zebra-crossing facilitates the pedestrians to cross the motorway.
Vehicles are not allowed to enter the pedestrian track is a punishable offence in almost all countries.
A bicycle track is a separate lane for bicycles. It is either a completely different route or a separate lane along the main highway.
A motorway carries cars, trucks, and buses. A motorway has different lanes for slow-moving and fast-moving vehicles.
Classification of highways based on topography
The roads travel across the lengths and breadths of the country. Due to the diverse topography of the region, highways pass through plains, hills and mountains. Thus, creating a basis for segregating the road type based on their topography and terrain.
A road passing through a plain area is known as a plain road. The ruling gradient for a plain road is 1:30 or 3.3%, and the limiting gradient is 1:20 or 5%.
A hilly road passes through the hills and has a mild to steep slope due to elevation change. The gradient for a hilly road is between 1:16.7-1:20.
A mountainous road has steep slopes and sharp turns. The limiting gradient is 1:16.7 or 6%. The exceptional gradient (1:14.3 or 7%) prevails over a very short stretch (lesser than 100 m). However, only a 2.5% gradient is permitted at hairpin bends.
Classification of highways based on usage
The roads usage may be affected due to the weather conditions. Rain and snow are common obstructions to road usage.
A road open for usage throughout the year is called an all-weather road. The road has the facility to drain off the rainwater. Also, the snow is removed off the road by equipment. All the expressways, national highways, state highways and district roads are all-weather roads.
Fair Weather Road
A fair-weather road only serves the traffic in clear weather. Village roads made with earth, murram or gravel become non-motorable in heavy rains and obstruct traffic movement.
Interested in reading how roads are made? Check out the road construction procedure.
Tunnels are a part of roads in mountainous regions. Learn about the various construction methods for tunnels.
Earthwork is an integral part of road works. Learn the complete earthwork procedure and quality control.
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