A road design is to build a strong base for the conveyance of traffic that has an improved surface for vehicles and pedestrians. Unlike the streets whose primary function is to serve as public spaces, the main function of road design is transportation. Furthermore, road design is a network channel between two cities, two places that help one move along with vehicles. Hence, it has various important roles and factors that decide what type of road design is suitable according to the place. Road design is a critical matter for governments to develop a proper chain of networks between cities and countries.
Planning and management of road designs are networks make the transport network efficient. Road designs are classified according to their function and level of importance. As a result, this classification approach helps to organize and prioritize road maintenance and construction, making transportation more efficient and safe.
Types of Road Design
The classification of road design depends on a few factors that guide one more on what kind of road design shall take place in a particular place.
1. Materials
Earthen Roads
This kind of road has layers of soil over the surface. They are suitable for low-traffic areas or rural areas. These roads must have good drainage systems for their better efficiency.
Gravel roads
These roads have small, fine gravel that is stronger than the earthen roads. This kind of road is a compact blend of gravel and earth, yet the pavement is a little weak.
Murrum Roads
This kind of road comprises of a material called murrums, which is a disintegration of igneous rocks by different weathering processes.
Water Bound Macadam Roads
These roads comprise crushed stone aggregates used in their base. After sprinkling water on the base, the stones and aggregates are spread and rolled. In terms of performance, these roads are better than earthen and gravel roads.
Wet Mix Macadam Road
Depending on the project needs and requirements, this kind of road design comprises of laying clean, crushed-grade aggregate and granular materials and compacting them to form a dense mass on a paved surface.
Bituminous road
These types of roads are the busiest roads and are suitable for the movement of heavy traffic areas. This type of road design comprises of a black, viscous, sticky material, which is a dense form of petroleum. They make the road design strong and efficient.
Concrete Roads
These types of roads for road design are very appropriate for areas with heavy traffic. These are the most common, but expensive, types of roads. They comprise of cement and take a longer time to construct.
2. Location and Function of Roads
National Highways
This kind of road design is the main highway that runs through the length and breadth of the country, connecting major ports, foreign highways, and capitals of state and union territories, as well as large industrial and tourist centres.
State Highways
This type of road design helps connect the state to the district headquarters and important cities within them. They also connect the state to national highways and highways in neighbouring states.
Major district roads
These kind of road design serves the purpose inside the districts as areas for markets and productions connecting them to main highways.
Village roads
This kind of road design serves the purpose of serving the districts as areas for markets and productions, connecting them to main highways.
3. Traffic Volume
Light roads
The roads that carry 70 vehicles per day are light roads. Such roads can are common in village areas where there is very little vehicular movement.
Medium roads
The roads with a capacity of 70–250 vehicles per day are medium roads. These roads are suitable to connect the state highways to other highways.
Heavy roads
When the vehicle carrying capacity of a road is up to 600, it is a heavy road.
Very Heavy roads
This kind of road can carry more than 600 vehicles at a time and has larger lengths and widths. These roads are the national highways.
4. Rigidity
Flexible Pavement
These types of road designs comprises of bituminous layers and subsequent base and sub-basecourses. The load transmits through grain-to-grain transfer from the surface.
Rigid Pavement
This kind of road design consists of a concrete base, which transfers the load through slab action or the bending action of the pavement slab.
Looking at the types of road design, one can decide what kind of road design is suitable for a particular project. Road design becomes crucial in terms of construction and development. Hence, following a few steps on how to design a road can be useful.
1. Considering the Volume of the Traffic
We tend to see the most important factor while doing a road design as the analysis of the movement on the road. This analysis will determine the volume of traffic on the road. This helps in the overall construction of the road. Road design determines the efficiency of the vehicles.
2. Giving proper access management
While doing a road design, the important aspect is its access management, as it serves two purposes: mobility and access. Properly implementing the access management strategies balances the competing needs of traffic mobility and safe access to adjusting properties.
3. Designing the Speed of the road
The materials and the dimensions of the road determine the speed of the vehicles over the roads. The geometric aspects of the road design would determine the speed limits of the road. The curvature radius of the road, the width and length of the road, and the finish of the surface determine at what speed the vehicles will be mobilising over the roads.
4. Designing level of service
A road design is considered appropriate when its level of service turns out to be efficient for the mobility of vehicles and traffic. The level of service in a road design includes travel time, speed, comfort, safety, convenience, and interruptions. This criterion differs from multi-lane highways according to density.
5. Roadway Context
For road construction to be successful, the road design has to consider its surroundings and respect them. The aspects of consideration include the people in the surrounding area and the environment. Studying and analysing the surrounding area would lead to better designs of cross sections, access, and lanes.
6. Clearing the Sight Distance
For road construction to be successful, the road design has to consider its surroundings and respect them. The aspects of consideration include the people in the surrounding area and the environment. Studying and analysing the surrounding area would lead to better designs of cross sections, access, and lanes.
7. Intersections of Road
Another important aspect of road design is the intersection of roads. While designing the intersection of roads, one must consider the traffic flow from both sides. The road intersections must have traffic signals to control the traffic and speeds of the vehicles over the road.
8. Traffic Lanes
This is one of the most important aspects of road design. The lane widths determine the flow of traffic on the road. Normally, the lane width of 12 feet is the basic lane width for any road. Lane widths must be within the assemblage of a given street, delineating space to serve all the needs, including travel lanes, safety islands, bike lanes, and sidewalks.
9. Traffic Islands at the intersection
In a road design, the traffic islands are the separators between motorised and non-motorised traffic participants. They are designed over the road to increase safety by preventing cars from cutting corners with potentially dangerous results.
10. Drainage at intersections
While doing a road design, considering the drainage is very crucial. Designing the drainage becomes mandatory to let the road be accessible while raining in an adequate manner. More storage of water over the roads can damage it structurally and also affect the mobility of the traffic. Appropriate horizontal and vertical alignment of intersections of roads and the selection of suitable elements dictates the drainage conditions of intersections.
11. Pedestrian flow Signage
Roads are equally important for pedestrians and vehicles. Road design includes the design of pedestrians in such a way that they are not placed near areas where vehicles travel faster than one can walk. Also, pedestrians must be away from areas with heavy vehicles. There must be proper signage for the pedestrians passing.
12. Cyclist Directions
Starting from the heavy vehicle traffic to the pedestrians, every mode of mobility has to be accessible on the road. There are areas in the cities on the road that are designed especially for cyclists to move. Designing these areas improves traffic mobility on the roads. Some places are used for mixed traffic at intersections, where these cyclists’ directions have to be designed crucially.
13. Traffic Sign and Equipment
A road design is not appropriate without the properly mentioned directions and equipment. The on-road equipment, such as traffic signals, lights, and planters, must be such that they do not hinder the traffic while traveling. The materials used for signboards must be such that they are visible from a distance.
14. Utility Infrastructure
Road design also has a factor of utility infrastructure along with its construction aspects. The utility infrastructure must pass outside the road’s surroundings or at a distance from the roadway. The shaft covers should be placed outside the roadway and only exceptionally on it.
15. Public Lighting
In the case of an intersection or point of access at a grade that envisages separate areas for pedestrians and cyclists, lighting for such intersections must be provided. Lighting poles shall be placed at a distance equal to 3–4 times their height.
For any road design, there are a few rules that have to be followed in India,
- The specifications for road works are based on the current Indian Road Congress Specifications and recommended codes of practice and the Ministry of Roads transport and highways as per IRC specifications.
- Roads shall be planned for the full width of the Right of way (ROW) available. In general, space for utility services may be identified separately by future requirements so that obstruction of roads and damage to pavement will not occur in the future.
- In general, the road designs are to be done over the next 20 years. In the absence of actual traffic growth by a suitable method, the annual growth rate of traffic may be adopted as 7.5%.
- A proper survey of the existing road will be carried out. All available information, such as grade of soil, year of construction, pavement composition, traffic, location of underground and overground utilities, etc., shall be considered.
- A land acquisition plan for an approved improvement proposal shall be prepared based on the collected revenue map and information.
- Normally, the median should not be less than 1.2 m, except for critical locations.
- Flexible pavement on new roads should be designed in accordance with IRC 37-2001.
- For structural design, only the number of commercial vehicles with a weight of 3 tonnes or more and their axle loading are considered.
- Rigid pavement should be proposed where the carriageway comes into submerged and low-lying areas.
- Passing places where provided should be based on actual needs, generally at the rate of 2-3 per km.
Conclusion
Road design is one of the most important factors in any area where a person has to mobilize. These roads are our daily way to reach places of work, social gatherings, and even our own homes. Starting from a small pedestrian to huge highways, road design is the way through which any life happens. Road design has become an important factor since the rise of urbanisation and globalization. It has included various elements and technologies in its development, design, and construction. Due to technological development, we have come across various materials that provide us with flexible solutions for the required road design. Studying the very basic rules and regulations for a road design, giving proper dimensions to the lanes, and providing appropriate access points and intersections is the way to efficient road design.
Content Writing And Research By: Ar. Rajeshwari Pandya Modi
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