Chapter 1

Highway
Role and Importance of Transportation
Transportation contributes to the economical, industrial, social and cultural development of any
country. In the production stage, transportation is required for carrying raw materials like seeds,
manure, coal, steel etc. in the distribution stage, transportation is required from the place of production
centers like the farms, and factories to the marketing places and later to the retailers and to the
consumers for distribution.

Importance of Transportation:
Following are the importance of transportation:
1. They plan an important role in the economic, social and commercial development of the
country.
2. They help in political development of country.
3. They improve the employment opportunities.
4. They help in cultural development in the country.
5. It plays a vital role in development of rural areas of the country.
6. It is essential for rushing aids to areas of the country.
7. It is essential to maintain the law and other in the country.
8. Improves the contact between two countries.
9. Enhances the import and export of the country
10. Improves the living standard of the country.
11. It improves the defense activities of the country.
12. It helps to improve science and technology
13. It helps in industrial development throughout the country.

Different modes of Transportation.

There are three basic modes of transportation, these are land, water and air.
Therefore there are four major modes of transportation:
1. Roadways OR Highways
2. Railways
3. Airways
4. Water ways
Other Modes of Transportation:
These include:
1. Pipe lines
2. Elevators
3. Belt conveyors
4. Cable cars
5. Aerial ropeways and
6. Monorails
 1. Roadways or Highways:
The roads or highways not only include the modern highway system but also the city
streets, feeder roads and village roads, catering for a wide range of road vehicles and the
pedestrians. This is the only mode which is giving maximum service to one and all and it has also
maximum flexibility for travel with reference to route, direction, time, cost and speed of travel etc. It
is possible to provide door to door service only by road transportation.

2. Airways:
The transportation by air is the fastest among the four modes. Air travel also provide more
comfort apart from saving in transportation time for the passengers and goods between the
airports unlike other modes of transport, air transport allows continuous journey over the land and
water, even across in accessible places in between two airport. The only limitation of this mode of
transportation is that energy required and overall operating cost is very high as compaired to all
other modes of transportation.

3. Waterways:
The transportation by water is the slowest among the four modes, but this mode needs
minimum energy to transport for unit load through unit distance. The transportation by water is
possible between the ports on the sea routes or along the rivers or canals where inland
transportation facilities are available.

4. Railways:
The transportation along the railway track becomes advantages by railways between the
stations both for the passengers and goods, particularly for longer distances. The energy
requirement to transport unit load through unit distance by railway is only a fraction of that required
by road (i.e., one fourth to one sixth). Therefore, it is advantageous to transport bulk goods through
railways.
Pipelines are used for the transportation of water, other fluids and even solid particles.

Introduction to Highways
Highway Engineering is a branch of transportation engineering which deals
with design, construction and maintenance of different types of roads. It is also called as road
engineering and it involves the study of the following:
i) Planning, location and development of roads
ii) Materials required for their construction
iii) Highway traffic performance and its control
iv) Drainage of roads etc.

Importance of roads or Highway Transportation

Roads or transportation or highway transportation is the means of detailed distribution between
shops, homes, factories, etc. It is only the roads which can carry the goods from and to railway stations,
aerodromes, harbors. Therefore the following are the importance of roads or highway transportation.
1. They provide conveyance to the people, goods, raw materials, manufactured articles, etc., to
reach different parts of the country.
2. They are the only source of communication in hilly regions.
3. They help in growth of business, trade and other economic activities in and outside the villages
and towns through connections.
 4. They help in efficient distribution of agricultural products and natural resources all over the
country.
5. Helps in agricultural development.
6. They help in price stabilization of commodities due to mobility of products all over the country.
7. They help in promoting the cultural and social ties among the people in different parts of the
country.
8. They improve the medical facilities.
9. Helps in dairy development
10. Forestry development
11. Helps in maintaining law and orders in country.
12. Helps in tourism development
13. They generate the more employment opportunities.
14. They improve the land value.
15. Helps in fisheries development
16. They serve as feeders for railways, airways and waterways
17. They play important role in defense activities.
18. They become the symbol of country’s progress and development.

Introduction to Road Alignment

Establishing the Centre line of the proposed road in plan on a ground is called road alignment.
The road alignment is very important. Improper road alignment may results in heavy capital
loss in construction or recurring loss in continuous heavy maintenance. Once a road is constructed it is
very difficult to change its alignment. Shifting of alignment may put all the major bridges and culverts
constructed at a very high cost, out of use, thus causing a great loss. Also cost of adjoining land and
shifting of the alignment.
Basic requirement of an Ideal Alignments
The following are the basic requirements of an ideal alignment of a road between two terminal stations:
1. Short: The alignment should be short so as to provide economy in the cost of construction,
maintenance and transportation. Therefore the alignment should be as straight as possible.
2. Easy: it should be easy for construction, maintenance and traffic operations, therefore the
alignment should have low gradients and flat curves.
3. Safe: it should be safe for traffic operations. Therefore the alignment should have well
designed geometrics, stable natural hill slopes and cut slopes as well as strong subgrade.
4. Economy: It should be economical in its cost of construction, maintenance and traffic
operations. Therefore the alignment should be free from excessive cutting and filling and it
should have less number for cross drainage works as bridges, culverts, causeways, etc.
5. Utility: the alignment should be of maximum utility, therefore the alignment should serve
maximum population by connecting intermediate important towns and group of villages.
6. Natural aspects: It should have good natural aspects. i.e. alignment should pass through
regions of natural beauty and scenery.

Factors Controlling the Road or Highway Alignment

The various factors controlling the alignments are:
1. Obligatory points
2. Traffic
3. Geometric design
4. Economics
5. Other factors
 1. Obligatory points:The points which control the alignment of a highway are known as
obligatory points. The control points may be sub divided into the categories.
a) Points through which alignment should pass.
b) Points through which alignment should not pass
c) The obligatory points through which alignment should pass often cause the alignment to
derivate from the shortest straight path as bridge site, mountain pass. Intermediate town or
quarry, etc.

Examples:
Bridge site: 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. Thus to locate
a bridge the highway alignment may be changed.
Mountain: while the alignment passes through a mountain, the various alternatives are to
either construct a tunnel or to go round the hills. The suitability of the alternatives depends on
factors like topography, site condition and construction and operation cost.
Intermediate town: The alignment may be slightly deviated to connect an intermediate town
or village nearby. These were some of the obligatory points through which the alignment
should pass.
The obligatory points through which road alignment should not pass also may make it
necessary to deviate from the proposed shortest alignment such as religious places, very costly
structures, unsuitable land as marsly land etc.

Examples:
Very costly structures: Acquiring such structures means heavy compensation which would
result in an increase in initial cost. So the alignment may be deviated not to pass through that
point.
Religious places: these have been protected by the law from being acquired for any purpose.
Therefore, these points should be avoided while aligning.

Lakes / ponds, etc : the presence of a lake or pond on the alignment path would also
necessitate deviation of the alignment.

2. Traffic: The road alignment should be decided based on the requirements of road traffic. Origin
and Destination study should be carried out in the area and the desire lines be drawn showing
the trend of traffic flow. The new road to be aligned should keep in view the desire lines,
anticipated traffic flow, classified traffic volume, their growth and future trends.
3. Geometric design:Geometric design factors such as gradient, radius of curve and
sight distance also would govern the final alignment of the highway. If straight
alignment is aimed at, often it may be necessary to provide very steep
gradients. As far as possible while aligning a new road, the gradient should be
flat and less than the ruling or design gradient. Thus it may be necessary to
change the alignment considering the design speed, maximum allowable
super elevation and coefficient of lateral friction. It may be necessary to make
adjustment in the horizontal alignment of roads keeping in view the minimum
radius of curve and the transition curves.
4. Economics: The alignment finalized based on the above factors should also be
economical. While working out the economics, the factors to be considered
are, (i) initial construction cost of the road, (ii) regular and periodic
maintenance cost of the road and (iii) vehicle operation cost in future years.
While trying to decrease the initial construction cost, either the future road
maintenance cost or vehicle operation cost or both of these may increase
considerably. Therefore while carrying out economic analysis, it is essential to
work out overall economics based on ‘life cycle cost’ of the road project and
not consider the initial cost of the road project only.
5. Other consideration: Various other factor which may govern either the
horizontal or vertical alignment of the road are drainage considerations,
hydrological factors, political considerations and monotony. The vertical
alignment is often guided by drainage consideration. The sub – surface water
level, seepage flow and high flood level are the factors to be kept in view,
while deciding the highway alignment.

Engineering Survey:
Before any highway alignment in finalized, various engineering surveys are
required to be conducted. The survey works carried out in four stages. These are:
1. Map study
2. Reconnaissance surveys
3. Preliminary Surveys and
4. Final location and detailed survey

1. Map study: the process of marking several possible alternative alignments of

a road on the topographic map of the area is known as map study.
The proposed alignment can be located on the map from the following
details.
i) Avoidable points. Such as ponds, valleys, lakes etc.
ii) Possibility of crossing through a mountain pass
iii) Approximate location of a bridge sight for crossing the river, avoiding bends,
etc.
iv) Two stations are situated at higher level and the other on lower level, etc.

2. Reconnaissance Survey: After map study and making various possible alternative
routes on the maps, reconnaissance survey is conducted along all the proposed
routes. In reconnaissance survey fairly wide stretch of land along all the marked routes
is studied. In this survey instruments like hand level, tangent clinometer, ghat – tracer.
A beny level, etc. Are used to collect following approximate data.

1. Gradients, radius of horizontal curves, etc. along alternative routes.

2. Position of hill rocks, lakes, ponds, valleys, ridges marshy land, water logged
lands, bridges on rivers. Built up areas and other features which are not marked on
available maps.
3. Maximum flood level, natural ground level, number and type of cross drainage
works along all the routes.
4. Type of soil along all the routes is also studied.
5. Position of quarries from where materials for road construction can be obtained, is
also marked. Availability of water and labor required during construction is also
probed.
6. For hilly areas, additional data like geological formation, type of rocks seepage
flow, slope of hill, rainfall etc. are also collected.
7. Approximate amount of earth work should also be estimated.
From data collected in the reconnaissance survey, proposed alignment
marked during map study may be altered at few points or may be completely changed
and finally one or more alternative route may be proposed for further study.
If area of study is large and undulated and time is short, then the
reconnaissance may be done aerially.
3. Preliminary survey: This survey is conducted along the alignments or routes
recommended after reconnaissance survey. The objective of this survey are:
1. To conduct survey (chain survey, plane table survey) and levelling along all the
routes recommended after reconnaissance to collect all necessary details.
2. To compare different proposal in view of the requirements of a good alignment of a
road.
3. To workout quantities of earth work, material of construction, etc. along all the
proposed routes.
4. To compare different routes with respect to the cost of construction and
maintenance and also bridges along each alternatives. Best alignment from all
consideration is lastly finalized.
Preliminary survey can be done by either conventional methods by using like
chain, plane table, level compass etc. or by taking aerial photographs.

4 .Final location survey and detailed survey: the detailed examination of the field
along the alignment finally recommended during the preliminary survey is
called location survey.
In this survey, the centre line of the route, finally recommended during
the preliminary survey, is first located on the ground. Then detailed survey is carried
out for collecting the information necessary for the preparation of plans and
construction details for the highway project.

In location survey, the survey instruments used are theodolite, level

levelling staves, plane table, steel tape etc.

Objects of final survey:

1. To fix the center line of the proposed road on the ground.
2. To collect field data necessary for the acquision of right – of – way.
3. To collect other details necessary for drafting of specifications, formation of rates,
computing of designs, preparation of constructions drawings for working out items
and quantities.