Unit-1

Introduction

1.1 Role of Transportation

Overview

2.     Social role of transportation

3.     Political role of transportation

4.     Environmental role of transportation

Overview

Transportation is a non separable part of any society. It exhibits a very close relation to the style of life, the range and location of activities and the goods and services which will be available for consumption. Advances in transportation has made possible changes in the way of living and the way in which societies are organized and therefore have a great influence in the development of civilizations. This chapter conveys an understanding of the importance of transportation in the modern society by presenting selected characteristics of existing transportation systems, their use and relationship to other human activities.

1. Economic role of transportation

Economics involves production, distribution and consumption of goods and services. People depend upon the natural resources to satisfy the needs of life but due to non uniform surface of earth and due to difference in local resources, there is a lot of difference in standard of living in different societies. so there is an immense requirement of transport of resources from one particular society to other. These resources can range from material things to knowledge and skill like movement of doctors and technicians to the places where there is need of them.

An example is given to evaluate the relationship between place, time and cost of a particular commodity. If a commodity is produced at point A and wanted by people of another community at any point B distant X from A, then the price of the commodity is independent on the distance between two centers and the system of transportation between two points. With improved system the commodity will be made less costly at B.

The reduction of cost of transport does not have same effect on all locations. Let at any point B the commodity is to be consumed. This product is supplied by two stations A and K which are at two different distances from B. Let at present the commodity supplied by A since it is at a lesser distance but afterwards due to improvement in road network between B and K, the point becomes the supply point of product.

2. Social role of transportation

Transportation has always played an important role in influencing the formation of urban societies. Although other facilities like availability of food and water play the major role, the contribution of transportation can be seen clearly from the formation, size and pattern, and the development of societies, especially urban centers.

From the beginning of civilization, the man is living in settlements which existed near banks of major river junctions, a port, or an intersection of trade routes. Cities like New York, Mumbai and Moscow are good examples.

The initial settlements were relatively small developments but with due course of time, the growing population and developed into big cities and major trade centers. The size of settlement is not only limited by the size of the area by which the settlement can obtain food and other necessities, but also by considerations of personal travels especially the journey to and from work. The increase speed of transport and reduction in the cost of transport has resulted in variety of spatial patterns.

When the cities grow beyond normal walking distance, then transportation Technology plays a role in the formation of the city. For example, main cities in the plains developed as a circular city with radial routes, where is the cities beside a river developed linearly. The development of automobiles and other factor like increase in personal income, and construction of paved road network, the settlements were transformed into urban centre of intense travel activity.

3. Political role of transportation

The world is divided into numerous political units which are formed for mutual protection, economic advantages and development of common culture. Transportation plays an important role in the following functioning of such political units.

The government of an area must be able to send/get information to and about its people. It may include loss to be followed, security and other need full information need to generate awareness. An efficient administration of a country largely depends on how effectively government could communicate this information to all the country. However, with the advent of communications, its importance is slightly reduced.

These choices may be classified as communication, military movement, and travel of persons and movement of freight. The primary function of transportation is the transfer of messages and information. It is also needed for rapid movement of troops in case of emergency and finally movement of persons and goods. The political decision of construction and maintenance of road has resulted in the development of transportation system.

4. Environmental role of transportation

The negative effects of transportation is more dominating than it's useful aspects as far as transportation is concerned full stop there are numerous categories into which the environmental effects have been categorized. They are explained in the following sections.

Growth of transportation has a very unfortunate impact on the society in terms of accidents. Worldwide death and injuries from road accidents have reached epidemic proportions and killed and about 15 million injured on the road accidents annually. Increase variation in the speed and vehicle density resulted in a high exposure to accident. Accident results in loss of life and permanent disability, and damage to the property. Accidents also cause numerous non quantifiable impacts like loss of time, grief to the near one of the victims, and inconvenience to the public.

All transport modes consume energy and the most common source of energy is from the burning of fossil fuels like coal, petrol and diesel etc. the relation between air pollution and respiratory diseases have been demonstrated by various studies and the detrimental effects on the planet earth is widely recognized recently.

Sound is acoustical energy released into the atmosphere by vibrating on moving bodies where as noise is unwanted sound produced. Transportation is a major contributor of noise pollution especially in urban areas. Noise is generated during both construction and operation. During construction and operation of large equipment causes considerable noise to the neighborhood. During the operation noise is generated by the engine and exhaust system of vehicle and aerodynamic friction and the interaction between the vehicle and support system.

The spectacular growth in industrial and economic growth during the past century has been closely related to an abundant supply of inexpensive energy from fossil fuels. Transportation sector is unbeliever to consume more than half of the petroleum products full stop the impact of the shortage of fuel was experience during major was when a strict rationing was imposed in many countries. The impact of this had cascading effects on many factors of societies especially in the price escalation of essential commodities.

Transportation directly or indirectly affects many other areas of society and few of them and are listed below

Key Takeaways

1.2 Modes of Transportation

Fig.1: Modes of transportation

2.     Railway transport

3.     Air transport

Key Takeaways

Modes of transport: The different modes of transport are air, water, and land transport, which include Rails or railways, road and off-road transport. Other modes also exist, including pipelines, cable transport, and space transport.

1.3 History of Road Development

6.     IRC played an important role in the formation of the three 20-year road development plans in India:

20-years Road Development Plans

Key Takeaways

IRC (Indian Road congress): The Indian Roads Congress (IRC) is the Apex Body of Highway Engineers in the country. The IRC was set up in December, 1934 on the recommendations of the Indian Road Development Committee best known as Jayakar Committee set up by the Govt. of India with the objective of Road Development in India. 

1.4 Road Types and Pattern

1.4.1 Road Types

Primary: Expressways & National Highways (NH)

Secondary: State Highways (SH) & Major District Roads (MDR)

Tertiary: Other District Roads (ODR) & Village Roads (VR)

2.     On the basis of usage during different seasons

All-weather Roads: negotiable during all weathers

Fair-weather Roads: negotiable during all weathers except monsoon season where streams may overflow across the road

3.     On the basis of road pavement

Paved Roads: provided with hard pavement surface which should be at least a Water Bound Macadam

Unpaved Roads: earth roads and gravel roads

4.     On the basis of pavement surfacing

Surface Roads: provided with bituminous or cement concrete surfacing

Un-surfaced Roads: not provided with bituminous or cement concrete surfacing

5.     Classification of rural & urban roads

Rural Roads: classified on the following basis –

a)     Traffic Volume – Heavy, medium or light

b)    Load Transport – Class A, Class B etc

c)     Location & Function

Urban Roads: classified into the following types –

a)     Arterial Roads

b)    Sub-arterial Roads

c)     Collector Streets

d)    Local Streets

1.4.2 Road pattern

The rectangular/ block/ grid pattern is a plan where the streets and roads are in the form of grids or blocks running perpendicularly into each other thus forming a grid or block. The North Nazimabad area of Karachi in Pakistan is a factual example of this type of pattern where the streets and roads run at an angle of ninety degree into each other. Usually in this type of pattern the streets and roads are far away from each other and it takes a long time to reach the center of the area or city.

2.     Radial Pattern

This type of network is a combination of radial and block pattern. A radial network of roads radiates from the center outwardly with block pattern network of roads in between the radial main streets. In this pattern, the entire area is divided into a network of roads radiating from the business outwardly. In between radiating main roads, the built-up area may be planned with rectangular block.

3.     Radial or star and circular pattern

In this system, the main radial roads radiating from central business area are connected together with concentric roads. In these areas, boundary by adjacent radial roads and corresponding circular roads, the built-up area is planned with a curved block system.

Advantages:

1)At traditional intersections with stop signs or traffic signals, some of the most common types of crashes are right-angle, left-turn, and head-on collisions. These types of collisions can be severe because vehicles may be traveling through the intersection at high speeds. With circular pattern, these types of potentially serious crashes essentially are eliminated because vehicles travel in the same direction.

2) Installing circular pattern in place of traffic signals can also reduce the likelihood of rear-end crashes.

4.     Hexagonal Pattern

This pattern is a network of roads that grow in such a manner in various directions forming hexagons. In this pattern the entire area is provided with a network of roads formatting hexagonal figures. At each corner of the hexagon, three roads meet the built-up area boundary by the sides of hexagons is further divided in suitable sizes.

Key Takeaways

1.5 Nagpur Road Plan

The Second World War saw a rapid growth in road traffic and this led to the deterioration in the condition of roads. To discuss about improving the condition of roads, the government convened a conference of chief engineers of provinces at Nagpur in 1943. The result of the conference is famous as the Nagpur plan.

A twenty-year development programmed for the period (1943-1963) was finalized. It was the first attempt to prepare a co-ordinate road development programmed in a planned manner.

The roads were divided into five classes:

Key Takeaways

1.6 Bombay Road plan & 3rd20-Year Road Plan

1.6.1 Bombay Road Plan

The length of roads was under the Nagpur plan was achieved by the end of it, but the road system was deficient in many respects. Accordingly, a 20 year plan was drafted by the roads wing of government of India, which is popularly known as the Bombay plan. The highlight of the plan was

●      It was the second-year road plan 1961 to 1981.

●      The total road length targeted to construct was about 10 lakhs.

●      Rural roads were given specific attention.

●      They suggested that the length of the rod should be increased so as to give a road density of 32 km per hundred square kilometers.

●      The construction of 1600 km of expressways was also then included in the plan.

1.6.2 3rd 20-Year Road Plan (Lucknow)

This plan has been prepared keeping in view the growth pattern envisaged in various held by the turn of the century. Some of the salient features of this plan are as given below:

This was the third 20-year road plan (1981-2001). It is also called Luck now road plan.

Key Takeaways

Energy conservation: Energy conservation is the effort made to reduce the consumption of energy by using less of an energy service. This can be achieved either by using energy more efficiently (using less energy for a constant service) or by reducing the amount of service used (for example, by driving less).

1.7 Highway Alignment & Location Survey

Engineering Surveys for Highway Alignment

The following steps are involved in finalizing the Highway alignment& preparing the project:

Map Study:

a)     Reconnaissance Survey:

b)    Preliminary Survey:

This is carried out to collect all the physical information which is necessary in connection with the proposed highway alignment. This work consists of:

This may be done using:

c)     Final Location & Detailed Survey:

Key Takeaways

1.8 Horizontal Profile

Overview

Horizontal alignment is one of the most important features influencing the efficiency and safety of a highway. A poor design will result in lower speeds and resultant reduction in highway performance in terms of safety and comfort. In addition, it may increase the cost of vehicle operations and lower the highway capacity. Horizontal alignment design involves the understanding on the design aspects such as design speed and the effect of horizontal curve on the vehicles. The horizontal curve design elements include design of super elevation, extra widening at horizontal curves, design of transition curve, and set back distance. These will be discussed in this chapter and the following two chapters.

Design Speed

The design speed, as noted earlier, is the single most important factor in the design of horizontal alignment. The design speed also depends on the type of the road. For e.g, the design speed expected from a National highway will be much higher than a village road, and hence the curve geometry will vary significantly.

The design speed also depends on the type of terrain. A plain terrain can afford to have any geometry, but for the same standard in a hilly terrain requires substantial cutting and filling implying exorbitant costs as well as safety concern due to unstable slopes. Therefore, the design speed is normally reduced for terrains with steep slopes.

Horizontal Curve

The presence of horizontal curve imparts centrifugal force which is reactive force acting outward on a vehicle negotiating it. Centrifugal force depends on speed and radius of the horizontal curve and is counteracted to a certain extent by transverse friction between the tyre and pavement surface. On a curved road, this force tends to cause the vehicle to overrun or to slide outward from the centre of road curvature. For proper design of the curve, an understanding of the forces acting on a vehicle taking a horizontal curve is necessary.

Fig.2: Horizontal Curve

They are the centrifugal force (P) acting outward, weight of the vehicle (W) acting downward, and the reaction of the ground on the wheels (RA and RB). The centrifugal force and the weight are assumed to be from the centre of gravity which is at h units above the ground. Let the wheel base be assumed as b units. The centrifugal force P in kg/m2 is given by

                                                                P =

where W is the weight of the vehicle in kg, v is the speed of the vehicle in m/sec, g is the acceleration due to gravity in m/sec2 and R is the radius of the curve in m.

The centrifugal ratio or the impact factor P/W is given by:

=

Key Takeaways

Super elevation: Super elevation is the transverse slope provided to counteract the effect of centrifugal force and reduce the tendency of vehicle to overturn and to skid laterally outwards by raising the pavement outer edge with respect to inner edge. Super elevation is represented by “e”.

1.9 Vertical Profile

Overview

The vertical alignment of a road consists of gradients (straight lines in a vertical plane) and vertical curves. The vertical alignment is usually drawn as a profile, which is a graph with elevation as vertical axis and the horizontal distance along the centre line of the road as the horizontal axis. Just as a circular curve is used to connect horizontal straight stretches of road, vertical curves connect two gradients. When these two curves meet, they form either convex or concave. The former is called a summit curve, while the latter is called a valley curve. This section covers a discussion on gradient and summit curves.

Gradient

Gradient is the rate of rise or fall along the length of the road with respect to the horizontal. While aligning a highway, the gradient is decided for designing the vertical curve. Before finalizing the gradients, the construction cost, vehicular operation cost and the practical problems in the site also has to be considered. Usually steep gradients are avoided as far as possible because of the difficulty to climb and increase in the construction cost. More about gradients are discussed below.

Effects of Gradient

The effect of long steep gradient on the vehicular speed is considerable. This is particularly important in roads where the proportion of heavy vehicles is significant. Due to restrictive sight distance at uphill gradients the speed of traffic is often controlled by these heavy vehicles. As a result, not only the operating costs of the vehicles are increased, but also capacity of the roads will have to be reduced. Further, due to high differential speed between heavy and light vehicles, and between uphill and downhill gradients, accidents abound in gradients.

Representation of gradient

The positive gradient or the ascending gradient is denoted as +n and the negative gradient as −n. The deviation angle N is: when two grades meet, the angle which measures the change of direction and is given by the algebraic difference between the two grades (n1 − (−n2)) = n1 + n2 = α1 + α2

Types of Gradient

Many studies have shown that gradient upto seven percent can have considerable effect on the speeds of the passenger cars. On the contrary, the speeds of the heavy vehicles are considerably reduced when long gradients as flat as two percent is adopted. Although, flatter gradients are desirable, it is evident that the cost of construction will also be very high. Therefore, IRC has specified the desirable gradients for each terrain. However, it may not be economically viable to adopt such gradients in certain locations; steeper gradients are permitted for short duration.

Key Takeaways

1.10 Factors Controlling the Alignment

We have seen the requirements of an alignment.

But it is not always possible to satisfy all these requirements. We have made a judicial choice considering all the factors.

Obligatory points

These are formed control points governing the highway alignment full stop these points are classified into two categories. Points pass through which it should pass and points through which it should not pass. Some of the examples are

The bridge can be located only where the river has straight and permanent path and also where the abutment and pier can be strongly founded. The road approach to the bridge should not be curved and skew crossing should be avoided as possible.

Why the alignment passes through a mountain, the various alternatives are to either construct a tunnel or to go around the hills. The suitability of the alternative depends on factors like topography, site conditions and construction and operation cost.

The alignment may be slightly divided to connect an intermediate town or village nearby.

Second category that is the points through which all the alignments should not pass are

These have been protected by the law from being acquired for any purpose. Therefore, this point should be avoided while alleging.

Acquiring such structures means heavy compensation which would result is an increase in initial cost. So, the alignment may be debited not to pass through that point.

The presence of a lake or pond on the alignment path would also necessitate deviation of the alignment.

The alignment should suit the traffic requirements. Based on the origin destination data of the area, the desire line should be drawn. The new alignment should be drawn keeping in view the desire line and traffic flow patterns etc.

Geometric design factors such as gradient, radius of curve, sight distance etc. also governs the alignment of the highway. To keep the radius of curve minimum, it may be required to change the alignment of the highway.  The alignment should be finalized such that the obstruction to visibility does not restrict the minimum requirements of sight distance. The design standards vary with the class of roads and the terrain and accordingly the highway should be aligned.

Key Takeaways

Alignment: Alignment is the position or layout of centre line of the highway on the ground is called the alignment. it includes straight path, horizontal deviation and curves. 

1.11 Survey for Route Location

Location of the highway alignment is done after carrying out a survey of the area.      These surveys are called Engineering Surveys. 

We have to locate an alignment which fulfils the basic requirements like the path must be short, safe, economic, easy and useful.

Engineering Surveys in the following phases:

This is the first step of the Engineering survey, using a topographic map of the area under consideration, which can be availed from the Survey of India. 

This topographic map, in general, has a contour interval of around 30 m to 40 m.

So, in the second phase/step a survey team is headed to the area under study with the minor surveying instruments like Abney level, Tangent Clinometers etc. to do a rough survey of the area under study. 

The rough survey is done along the alternatives proposed in the map study and feasibility of the road alignment is checked along the different routes. 

Some of the routes may be cancelled out or they may be changed if they appear to be impossible in this study. So finally they will have a set of routes which are to be further studies in the next step.

In this step, the alternative routes which are proposed after a rough survey in the second step are surveyed in details using some advanced instruments like levels, chain and theodolite. Aerial Photogrammetry is best suited for this type of survey.
All the necessary details to carry out the comparative study of the different routes are collected and then finally we have to decide one alignment best suited for the alignment of the road.

Here various details are found out along the stretches of the routes, which can also be found using the aerial techniques by taking photographs along the routes and then further processed to find out the final details of the area.    

Location of the centerline of the road is done with very much precise instrument like Theodolite and Chain using the drawing prepared or the details gathered in the third step (i.e. Preliminary survey). This is done by staking the ground with the stakes inserted at the intervals of 50 m to 100 m in the plain area, 50 m to 75 m in the rolling terrain and 30 m to 50 m in the hills and steep terrain.

Pegs may be driven at all the control points. At the curves control points, starting of the transition curve, starting off the circular curve and terminal of the circular curve and the terminal of the transition curve the pegs/stakes are driven into the ground to firmly locate these control points. Benchmarks are located at an interval of 250 m and they are necessarily located at the sites of the cross drainage works.

In this part, we have carried out the detailed study of the final route using some very precise instruments like Theodolite and Chain to gather all the necessary data for the final estimation, design and preparing drawings using which the construction can be started. A detailed project report is to be prepared and all the necessary data is collected to prepare that report.

So, the profiling, cross-sectioning and soil investigation are carried out very precisely. CBR values are also found to find out the design thickness of the pavement. After collecting the data a final drawing a report is prepared which concludes the highway planning part. 

Key Takeaways

Aerial Photogrammetry: Aerial digital photogrammetry, often used into pographical mapping, begins with digital photographs or video taken from a camera mounted on the bottom of an airplane.

References

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3.     LR Kadiyali, Transportation Engineering, Khanna Publication.

4.     L.R. Kadiyali, Transportation Engineering, Khanna Publishing House

5.     Saxena, Subhash C, A Textbook of Highway and Traffic Engineering, CBS Publishers &Distributers, New Delhi

6.     Kumar, R Srinivasa, “A Text book of Highway Engineering”, Universities Press,Hyderabad.

7.     Kumar, R Srinivasa, “Pavement Design”, Universities Press, Hyderabad.

8.     Chakraborty Partha & Das Animesh., “Principles of Transportation Engineering”,Prentice Hall (India), New Delhi,

9.     IRC: 37- Latest revision, “Tentative Guidelines for the design of Flexible Pavements”Indian Roads Congress, New Delhi

10. IRC:58-2015 Guidelines for the Design of Plain Jointed Rigid Pavements for Highways(Fourth Revision) (with CD)

11. IRC:65-2017 Guidelines for Planning and Design of Roundabouts (First Revision)

12. IRC:73-1980 Geometric Design Standards for Rural (Non-Urban) Highways

13. IRC:106-1990 Guidelines for Capacity of Urban Roads in Plain Areas

14. IRC:93-1985 Guidelines on Design and Installation of Road Traffic Signals.

15. IRC:92-2017 Guidelines for Design of Interchanges in Urban Areas (First Revision)

16. IRC: SP: 68-2005, “Guidelines for Construction of Roller Compacted Concrete Pavements”,Indian Roads Congress, New Delhi.

17. IRC: 15-2002, “Standard Specifications and Code of Practice for construction of ConcreteRoads” Indian Roads Congress, New Delhi.

18. MORTH, “Specifications for Road and Bridge Works”, Ministry of Shipping, RoadTransport & Highways, Published by Indian Roads Congress, New Delhi.