CONTENT- Modes of transportations, their importance and limitations, the importance of highway transportation. Highway Development and Planning: Principles of Highway planning.  Road development in India, NHAI, NHDP, PMGSY, MSRDC. Classification of roads, road network patterns, Planning Surveys.  Terrain classification, design speed, vehicular characteristics, highway cross-section elements.  Sight distance: introduction to sight distance, reaction time, analysis of safe sight distance, analysis of overtaking sight distance, intersection sight distance. 

1. Unit 1
Introduction to Highway
Engineering
Ms. Priya Sarita Mane

2. “
CONTENT
▣ Modes of transportations, their importance and limitations, the importance of highway
transportation. Highway Development and Planning: Principles of Highway planning.
▣ Road development in India, NHAI, NHDP, PMGSY, MSRDC. Classification of roads, road
network patterns, Planning Surveys.
▣ Terrain classification, design speed, vehicular characteristics, highway cross-section
elements.
▣ Sight distance: introduction to sight distance, reaction time, analysis of safe sight distance,
analysis of overtaking sight distance, intersection sight distance.
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3. Transportation
▣ A transportation system may be defined as consisting of the fixed facilities, the flow entities and
the control system.
▣ Transportation contributes to the economic, industrial, social and cultural development of any
country.
▣ Transportation is vital for the economic development of any region since every commodity
produced whether it is food, clothing, industrial products or medicine needs transport at all
stages from production to distribution.
▣ The adequacy of transportation system of a country indicates its economic and social
development.
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4. Modes of transportation
▣ Primary Modes
○ Roadways or Highways
○ Railways
○ Waterways
■ Inland
■ Coastal
■ Ocean
○ Airways
■ Domestic
■ International
▣ Secondary Modes
○ Ropeways
○ Pipelines
■ Water
■ Gas
■ Sewer
○ Canals
■ Irrigation Canal
■ Storm water drainage
ditch
o Belt conveyers
4

5. Roadways or Highways
▣ The transportation by road is the only mode which could give maximum service to one and all.
▣ This mode has also maximum flexibility for travel with reference to route, direction, time and speed
of travel etc. through any mode of road vehicle.
▣ It is possible to provide door to door service only by road transport.
▣ The other three modes, viz. airways, waterways and railways have to depend on transportation by
roads for the service to and from their respective terminals, airports, harbours or stations.
▣ The roads or highways not only include the modern highway system but also to provide independent
facilities for road travel by a well-planned network of road throughout the country, feeder roads,
city roads, village roads and pedestrians. But other modes do not provide such type of more facilities.
Railways
▣ The transportation along the railway track could be advantageous by railway between the stations
both for the passenger and goods, particularly for longer distances.
▣ The energy requirement to haul unit load through unit distance by railway is only a fraction (¼th -
⅙th) of that required by road.
▣ Hence full advantage of this mode should be taken for the transportation of bulk goods along land
where the railway facilities are available. 5

6. Waterways
▣ Transportation by water is the slowest among the four modes; but this mode needs
minimum energy to haul unit load through unit distance.
▣ The transportation by water is possible between the parts on the sea routes or along the
rivers or canals where inland transportation facilities are available.
Airways
▣ The transportation by air is the fastest among four modes.
▣ Air travel also provides more comfort apart from saving in transportation time for the
passengers and the goods between airports.
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7. Role of transportation (infrastructure) in development of a nation
Infrastructure development in which transportation is the major factor contributing to the economic,
social and cultural development of any country.
1. Economic role:
(i) The natural resources needed for food, clothing and shelter are to be transported from the place of
production to the place of demand.
(ii) The produced things like medicines, industrial products, etc. need transport for distribution.
(iii) Inadequate transportation facilities slow down the economic growth of a nation.
2. Social role:
(i) Decentralization of the population centers away from the congested areascan be effectively done if
proper transportation system is provided.
(ii) Under-developed areas can be developed by connecting them to developed areas by
transportation systems.
(iii) Frequent travels in other parts of the country and outside the country gives opportunity
for exchange of information, knowledge, culture, etc.
(iv) Better international relations can be established through efficient transportation systems.
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8. 3. Safety role:
(i) Efficient transportation system is needed for rushing help to affected areas in events like
floods, earthquakes, fire hazards, epidemics, etc.
(ii) Transportation helps in maintaining law and order.
4. Strategic role:
Transportation is important for strategic movements like movements of army, ammunition, etc.
in war-like emergency.
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9. Advantages and Limitations of Highway over other Modes
Advantages
o Roads are used by various types of vehicles; like passenger cars, buses, trucks, two and three
automobiles, cycles etc. But railway tracks are used only by rail locomotives and wagons; waterways
are used only by ships and boats.
o Road transport requires relatively small investment, since motor vehicles are much cheaper than
other carriers like rail locomotives and wagons, water and air carriers.
o Construction and maintenance of roads are also cheaper than that of railway tracks, docks, harbours
and airports.
o Road transport offers a complete freedom to road users to transfer the vehicle from one lane to
another. This flexibility of changes in location, direction, speed and timing of travel is not available
to other modes of transport.
o In particular for short distance travel, road transport saves time.
Disadvantages
o Road transport is subjected to a high degree of accidents due to flexibility of movements offered to
the road users, than other modes of transportation.
o It consist more land coverage and also takes more area for parking.
o It is more energy consuming and environmental polluting than other modes.
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10. Highway Development and Planning
History of highway engineering
The history of highway engineering gives us an idea about the roads of ancient times. Roads in Rome
were constructed in a large scale and it radiated in many directions helping them in military
operations. Thus they are considered to be pioneers in road construction.
o Ancient roads
o Roman roads
o British roads
o French roads etc.
Ancient Roads
The first mode of transport was by foot. These human pathways would have been developed for specific
purposes leading to camp sites, food, streams for drinking water etc.
The next major mode of transport was the use of animals for transporting both men and materials. Since
these loaded animals required more horizontal and vertical clearances than the walking man, roads with
harder surfaces emerged.
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To provide adequate strength to carry the wheels, the new ways tended to follow the sunny drier side of a
path. These have led to the development of foot-paths. After the invention of wheel, animal drawn vehicles
were developed and the need for hard surface road emerged. Traces of such hard roads were obtained from
various ancient civilization dated as old as 3500 BC. The earliest authentic record of road was found from
Assyrian empire constructed about 1900 BC.
In the case of heavy traffic, a surface course of large 250 mm thick hexagonal flag stones were provided. The
main features of the Roman roads are that they were built straight regardless of gradient and used heavy
foundation stones at the bottom. They mixed lime and volcanic pozzolana to make mortar and they added
gravel to this mortar to make concrete. Thus concrete was a major Roman road making innovation.
Roman roads
The earliest large scale road construction is attributed to Romans who constructed an extensive system
of roads radiating in many directions from Rome.
They were a remarkable achievement and provided travel times across Europe, Asia minor, and
north Africa. Romans recognized that the fundamentals of good road construction were to provide
good drainage, good material and good workmanship.
Their roads were very durable, and some are still existing. Roman roads were always constructed on a firm -
formed subgrade strengthened where necessary with wooden piles. The roads were bordered on both sides
by longitudinal drains.
Road formation up to a 1 meter high and 15 m wide and was constructed with
materials excavated during the side drain construction. This was then topped with a sand leveling course.

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British roads
The British government also gave importance to road construction. The British engineer John
Macadam introduced what can be considered as the first scientific road construction method. Stone size
was an important element of Macadam recipe. By empirical observation of many roads,he came to
realize that 250 mm layers of well compacted broken angular stone would provide the same strength and
stiffness and a better running surface than an expensive pavement founded on large stone blocks. Thus
he introduced an economical method of road construction.
The mechanical interlock between the individual stone pieces provided strength and stiffness to the
course.
But the inter particle friction abraded the sharp interlocking faces and partly destroy the effectiveness of
the course. This effect was overcome by introducing good quality interstitial finer material to produce a
well-graded
mix.

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French roads
The next major development in the road construction occurred during the regime of Napoleon.
The significant contributions were given by Tresaguet in 1764 .He developed a cheaper method
of construction than the lavish and locally unsuccessful revival of Roman practice.
The pavement used 200 mm pieces of quarried stone of a more compact form and shaped such that
they had at least one flat side which was placed on a compact formation. Smaller pieces of broken
stones were then compacted into the spaces between larger stones to provide a level
surface. Finally the running layer was made with a layer of 25 mm sized broken stone. All this structure
was placed in a trench in order to keep the running surface level with the surrounding country side. This
created major drainage problems which were counteracted by making the surface as impervious as
possible, cambering the surface and providing deep side ditches.
Construction steps
•Subgrade is compacted and prepared with cross slope of 1 IN 36 up to a desired width (about 9 m).
•Broken stones of a strong variety, all passing through 5 cm size sieve were compacted to a uniform
thickness of 10 cm.
•The second layer of strong broken stones of size 3.75 cm was compacted to thickness of 10 cm.
•The top layer consisted of stones of sizes less than 2 cm compacted to a thickness of about 5 cm and
finished so that the cross-slope of pavement surface was also 1 in 36.

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15. 15

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HIGHWAY DEVELOPMENT IN INDIA
• India has embarked on a rapid pace of road development since after late 1990s by giving a high priority to
highway development. The back ground to this is the economic liberalization that was kick-started in 1992.
• The National Highway Development Programme (NHDP) was the first major programme launched in 1997 to
develop a large highway network across the country.
• The Public Private Partnerships (PPP) was adopted as a means of road and highway development in India
starting from 2001, given the larger challenges and the need for leveraging private investments into the sector.
Pursuant to it, a large number of contracts were awarded under Build, Operate and Transfer (BOT) variants of
PPP and other PPP models.
• India had a network of roads in the ancient times. The road development in India can be discussed by taking
different phases of the history at one time.
Ancient Times
• The excavation of the Mohn-Jodaro and Harappa civilization shows the traces of the roads in
the ancient Indian times, in a period of 35th to 25th B.C.
• Old records reveal that in early periods the roads were considered indispensable for administrative and
military purpose. The ancient scriptures refer to existence of roads during the Aryan period in the 4th century
B.C.
• In the beginning of 5th century A.D., emperor Ashoka had improved the roads and provided facilities for
travelers.

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Mughal period and Road construction:
•The Mughal and Pathans improved the quality of the roads in India.
•Some of highways either built or maintained by Mughals received great appreciation form the foreign visitors who
visited during this period.
•Sher Shah Suri is still remembered for the construction of the Grand Trunk Road(GT Road) from Bangladesh-India to
Kabul in Afghanistan.
19th Century and Road Construction in India:
•After the fall of the Mughal Empire in India in 19th century the Britishers participated in the road construction for the
military and administrative purposes.
•The work was carried out by the British Military Engineers.
•Railway was introduced later but the existing roads were metalled and bridges were provided. Dalhousie in the mid of
19th century introduced the Public works department (PWD), which still runs the various public works in India.
•Later after the introduction of the railways in India the attention was shifted to the railways construction and only the
feeder roads and railways got the prime importance afterwards.
Road development in India during Twentieth Century:
•During the second decade of the 20th century, soon after the First World War the motor vehicles using the roads in
India also increased and this demanded better roads.
•However, the roads that existed then with ‘Water Bound Macadam (WBM)’ surface and other inferior surfaces were
not able to withstand the mixed traffic consisting of slow-moving vehicles and the motor vehicles.

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•Due to the combined effect of the mixed traffic movement, the roads deteriorated fast during the post-war period.
Formation of Jayakar Committee
A resolution was passed by both Chambers of the Indian Legislature in the year 1927 for the appointment of a
committee to examine and report on the question of road development in India. In response to the resolution, a Road
Development Committee was appointed by the Government in 1927, with Mr. M. R. Jayakar as the Chairman.
Recommendations
Over a period after the First World War, motor vehicles using the roads increased and this demanded a better road
network which can carry mixed traffic conditions. The existing roads when not capable to withstand the mixed traffic
conditions. For the improvement of roads in India government of India appointed Mr. Jayakar Committee to study the
situations and to recommend suitable measures for road improvement in 1927 and a report was submitted in 1928
with following recommendations
1) The road development in the country should be considered as a national interest as this has become beyond the
capacity of provincial governments and local bodies.
2) An extra tax should be levied on petrol from the road users to develop a road development fund called ‘Central
Road Fund’
3) A Semi-official technical body should be formed to pool technical know-how from various parts of the country
and to act as an advisory body on various aspects of roads.
4) A research organization should be instituted to carry out research and development work pertaining to roads and to
be available for consultations.

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IMPLEMENTATIONS:
Majority of the recommendations were accepted by the government implemented by Jayakar Committee.
Some of the technical bodies were formed such as,
1) Central Road Fund (CRF) in 1929
2) Indian Road Congress (IRC) in 1934
3) Central Road Research Institute (CRRI) in 1950.
Central Road Fund (CRF):
1) Central Road Fund (CRF) was formed on 1st March 1929
2) The consumers of petrol were charged an extra levy of 2.64 paisa/liter of petrol to build up this road development
fund.
3) From the fund collected 20 percent of the annual revenue is to be retained as meeting expenses on the
administration of the road fund, road experiments and research on road and bridge projects of special importance.
4) The balance 80 percent of the fund to be allotted by the Central Government to the various states based on actual
petrol consumption or revenue collected
5) The accounts of the CRF are maintained by the Accountant General of Central Revenues.
6) The control of the expenditure is exercised by the Roads Wings of Ministry of Transport.

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B) Indian road congress (IRC):
1) It is a semi-official technical body formed in 1934. It was formed to recommend standard specifications.
2) It was constituted to provide a forum of regular technical pooling of experience and ideas on all matters affecting
the planning, construction and maintenance of roads in India.
3) IRC has played an important role in the formulation of the 20-year road development plans in India.
4) Now, it has become an active body of national importance controlling specifications, guidelines and other special
publications on various aspect of Highway Engineering.
C) Central road research institute (CRRI):
1) CRRI was formed in the year 1950 at New Delhi
2) It was formed for research in various aspect of highway engineering
3) It is one of the National laboratories of the Council of Scientific and Industrial Research.
4) This institute is mainly engaged in applied research and offers technical advice to state governments and the
industries on various problems concerning roads.
Motor vehicle act (1939):
The increased numbers of vehicle on the Indian roads demanded for the rules and regulations.
The motor vehicle act was passed in 1939, which laid down the rules for the road users and 7 also for the identity of
the vehicles.
It is still running in the country in almost same way as it was at that time.

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First 20-years road plan (Nagpur Road Plan-1943 to 1963):
The first 20 years road network plan was prepared in the meeting of the Chief Engineers from the various
parts of the country at the Nagpur, in 1943, which is also known as the Nagpur road plan.
It was the first ever major planning which contributed a lot for the development of the roads in the
country.
It classified the Indian roads according to their location and purpose, and also it laid down a target for a
density of road network of 16 km per 100 sq. Km in the country at the end of the 20 years road network in
the year 1963.
After the starting of the 5 years plans in the year 1951, the first two 5 years plans also contributed to the
target set by the first 20 years plan of the Nagpur so the density of 16 km per 100 sq. Km was achieved in
the year 1961, 2 years earlier to the target year.
Second 20-years road plan (Mumbai Road Plan- 1961 to 1981):
As the earlier target was achieved before the planned year, so a need to set a new target arises and another
20 years road plan was laid down at the meeting of the various authorities from different states at
Bombay.
The road density target was doubled this time.

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Third 20-years road plan (Lucknow road congress 1984)
This plan has been prepared keeping in view the growth pattern envisaged in various fields 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 Lucknow road plan.
It aimed at constructing a road length of 12 lakh kilometres by the year 1981 resulting in a road density of 82kms/100
sq.km.
The plan has set the target length of NH to be completed by the end of seventh, eighth and ninth five year plan
periods.
It aims at improving the transportation facilities in villages, towns etc. such that no part of country is farther than 50
km from NH.
Vision 2010 focus on 20km of road/day. More than 1.6L tonne bitumen per year produced from 12 refineries and
more than 4L cr spend on road. but not withstand after one rain.

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Highway Planning
Highway design is only one element in the overall highway development process.
Historically, detailed design occurs in the middle of the process, linking the preceding
phases of planning and project development with the subsequent phases of right-of-way
acquisition, construction, and maintenance.
While these are distinct activities, there is considerable overlap in terms of coordination
among the various disciplines that work together, including designers, throughout the
process.
It is during the first three stages, planning, project development, and design, that designers
and communities, working together, can have the greatest impact on the final design
features of the project.
In fact, the flexibility available for highway design during the detailed design phase is
limited a great deal by the decisions made at the earlier stages of planning and project
development.
This Guide begins with a description of the overall highway planning and development
process to illustrate when these decisions are made and how they affect the ultimate design
of a facility.
Planning
Project development
Final Design
Right of way
Construction

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Objectives of Highway Planning:
Planning if considered as pre-requisite before attempting any development program in the present era. Highway
planning is of great importance when funds available are limited whereas the total planning is of great importance
when the funds are limited whereas the total requirement is much higher.
The objectives are as follows :
To plan the overall road network for efficient and safe traffic operations, but at minimum cost. Here the costs of
construction, maintenance and resurfacing or strengthening of pavement layers and vehicle operation costs are taken
into consideration.
To arrive at the road system and the lengths of different categories of roads which could provide maximum utility
and could be constructed within the available resources during the plan period under construction
To divide the overall plan into phases and to decide priorities.
To fix up date wise priorities for development of each road link based on utility as the main criterion for phasing the
road development program.
e) To plan for the future requirements and improvements of roads in view of anticipated developments.
f) To work out suitable financing systems.
•To fulfil these objectives, the following principles have to be borne in mind:
a)The proposed road links should be a part of the planned road network for the state/nation.
b)The importance of the road shall be based on the traffic demand, and hence its type should fall under the standard
classification.
c)The maintenance needs of the roads should receive prompt attention by setting aside funds for this purpose.
d)Statutory provisions for traffic regulation should be in place.

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Road Development In India
The first attempt for proper planning of the highway development programme in India on a long-term basis was
made at the Nagpur Conference in 1943.
After the completion of the Nagpur Road Plan targets, the Second Twenty year Plan was drawn for the period
1961- 1981.
The Third Twenty Year Road Development Plan for the period 1981-2001 was approved only by the year 1984.
The fourth 20-year road development plan of the country for the period 2001 – 2021 has not yet been approved as
an official plan document, instead ‘Roads Development Vision: 2021’ has been formulated.
First 20-Year Road Plan (Nagpur Road plan)
This plan was formed in the year 1943 at Nagpur and plan period was from 1943- 1963.
Two plan formulae were finalized at the Nagpur Conference for deciding two categories of road length for the
country as a whole as well as for individual areas (like district).
This was the first attempt for highway planning in India.
The two plan formulae assumed the Star and Grid pattern of road network. Hence, the two formulae are also called
“Star and Grid Formulae”.
Salient Features of Nagpur Road Plan
All the roads were classified into 5 categories namely
1) National Highways (NH)
2) State Highways (SH)
3) Major District Roads (MDR)
4) Other District Roads (ODR)
5) Village Roads (VR)

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Two plan formulas were suggested for deciding the length of two categories of roads as given below
Category – 1: Surfaced or metaled roads meant for NH/SH/MDR
Category – 2: Unsurfaced roads meant for ODR/VR
Nagpur road plan aimed at achieving a modest average road density of 16km per square km area.
Second Twenty Year Road Plan (Bombay Road Plan):
As the target road length of Nagpur road plan was completed nearly earlier in 1961 a long-term plan was initiated
for twenty-year period which was initiated by IRC.
Hence, the second twenty year road plan came into picture which was drawn for the period of 1961-81.
The second twenty year road plan was envisaged overall road length of 10, 57,330 km by the year 1981.
Salient Features of Second 20-year Road Plan
Every town with population above 2000 in plains should be connected by a bituminous road or metaled road,
above 1000 in semi-hilly area above 500 in hilly area
1600 km length of expressways was proposed.
Development allowance is 5% only.
Length of railway track was not deducted.
Five equations are given to find NH/SH/MDR/ODR/VR.

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Third Twenty Year Road Plan (Lucknow Road Plan):
The Third twenty year road plan was prepared by the Road Wing of the Ministry of Shipping and Transport with the
active co-operation from a number of organizations and the experts in the field of Highway Engineering and
Transportation.
This document was released during the 45th Annual Session and the Golden Jubilee celebrations of the Indian Road
Congress in February 1985 at Lucknow.
Therefore, this plan for 1981-2001 is also called as ‘Lucknow Road Plan’.
Salient Features of Second 20-year Road Plan
The future road development should be based on the revised classification of road system consisting of Primary,
secondary and tertiary systems.
The road network should be developed so as to preserve the rural oriented economy and to develop small to towns with
all the facilities. All the villages with population above 500 should be connected with all-weather roads by the end of
the century.
The overall road density should be increased to 82 km per 100 sq. km area by the year 2001 and 40km for hill areas of
altitude up to 2100m and 15km for altitude over 2100m.
The NH network should be expanded to form square grids of 100km sides so that no part of the country in more than
50km away from a NH.
The length of SH and MDR required should be decided based on the areas and no. of towns with population above 5000
in the state or region.
Expressway should be constructed along the major traffic corridors to provide fast travel.
All the towns and villages with population above 1500 should be connected by MDR and villages with population 1000
to 1500 by ODR. There should be road within a distance of

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3km in plain and 5km in hilly terrain connecting the villages with population less than 500.
Roads should be built in less industrialized areas to attract the growth of industries.
Long term master plans for road development should be prepared at various level i.e., taluk, district, state and national
level. The road network should be scientifically decided to provide maximum utility.
The existing roads should be improved by rectifying the defects in the road geometrics, widening of the pavements,
improving the riding quality of the pavement surface and strengthening of pavement structure
There should be improvements in environmental quality and road safety.
Road length by 3rd 20-year road development plan
Length of NH – 1km per 50sq. km area.
Length of SH
By total area – SH, km = Area of the state, sq.km/25
2) By total no of town and area in the state, SH, km =
(62.5 x No towns in the state – area of the state, sq. km)
50
Adopt length of SH (higher of the two criteria)
c) Length of MDR
By total area – MDR, km = Area of the state, sq.km/12.5
2) By total no of town and area in the state, MDR, km = 90 x No. of towns in the state.
Adopt length of SH (higher of the two criteria).

29. Present Scenario Of Road Development In India
29
1.National Highway Development Projects (NHDP)
Realizing the deficiencies in the National Highway System in the country the National Highways Authorities of India
(NHAI) took up the National Highways Development Projects (NHDP) by the year 2000 in different phases.
The National Highways Development Project (NHDP) is a project to upgrade, rehabilitate and widen major highways
in India to a higher standard.
The project was started in 1998 under the leadership of then Prime Minister, Atal Bihari Vajpayee.
National Highways account for only about 2% of the total length of roads, but carry about 40% of the total traffic
across the length and breadth of the country.
This project is managed by the National Highways Authority of India (NHAI) under the Ministry of Road, Transport
and Highways.
The NHDP represents 49,260 km of roads and highways work and construction in order to boost economic
development of the country.
The government has planned to end the NHDP program in early 2018 and consume the ongoing projects under a
larger Bharatmala project.
NHDP Phase I : NHDP Phase I was approved by Cabinet Committee on Economic Affairs (CCEA) in December
2000 at an estimated cost of Rs.30,000 crore comprises mostly of GQ (5,846 km) and NS-EW Corridor (981km), port
connectivity (356 km) and others (315 km).

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•NHDP Phase II : NHDP Phase II was approved by CCEA in December 2003 at an estimated cost of Rs.34,339 crore
(2002 prices) comprises mostly NS-EW Corridor (6,161 km) and other National Highways of 486 km length, the total
length being 6,647 km. The total length of Phase II is 6,647 km.
•NHDP Phase-III: Government approved on 5.3.2005 upgradation and 4 laning of 4,035 km of National Highways on
BOT basis at an estimated cost of Rs. 22,207 crores (2004 prices). Government approved in April 2007 upgradation
and 4 laning at 8074 km at an estimated cost of Rs. 54,339 crore.
•NHDP Phase V: CCEA has approved on 5.10.2006 six laning of 6,500 km of existing 4 lane highways under NHDP
Phase V (on DBFO basis). Six laning of 6,500 km includes 5,700 km of GQ and other stretches.
•NHDP Phase VI: CCEA has approved on November 2006 for 1000 km of expressways at an estimated cost of Rs.
16680 crores .
•NHDP Phase VII: CCEA has approved on December 2007 for 700 km of Ring Roads, Bypasses and flyovers and
selected stretches at an estimated cost of Rs. 16680 crores .
2. NHAI (National Highways Authority of India)
The National Highways Authority of Indi is an autonomous agency of the Government of India, responsible for
management of a network of over 70,000 km of National Highways in India. The Authority is a nodal agency of the
Ministry of Road Transport and Highways (MORTH). The NHAI was constituted by the National Highways
Authority of India Act, 1988. It is responsible for the development, maintenance, management and operation of
National Highways. The NHAI has to implement the National Highway Development Project (NHDP). The NHDP
is under implementation in the following phases,

31. Phase I: Approved in December 2000, at an estimated cost of Rs. 30,000 crores. It
includes the Golden Quadrilateral (5846 km), the NS-EW Corridors (981 km), port connectivity (356 km)
and others (315 km). The GQ connects the four major cities Delhi, Mumbai, Chennai and Kolkata.
Phase II: Approved in December 2003, at an estimated cost of Rs. 34339 crores. It includes
the completion of the NS-EW Corridor (7300 km) and another 486 km of highways. NS and EW
corridors comprising national highways connect four extreme points of the country. The NS
corridor connects Srinagar in North to Kanyakumari in South. The EW corridor connects Silchar in East
to Porbandar in West.
Phase III: This phase was approved in 2005 and 2006; at an estimated cost of Rs. 76500 crores. It
includes an upgrade to 4-lanes of 12, 109 km of National Highways on BOT (Build, Operate and Transfer)
basis.
Phase IV: It includes widening of 20, 000 km highways that were not part of Phase I, II or III. The
existing single lane highways will be converted into two lanes with paved shoulders.
Phase V: Approved in October 2006, it includes upgrades to 6-lanes for 6,500 km, of which 5,700 km is
on the GQ. This phase is entirely on a DBFO (Design, Build, Finance and Operate) basis.
Phase VI: This phase, approved in November 2006, will develop 1,000 km of expressways at an
estimated cost of Rs. 167000 crores.
Phase VII: This phase, approved in December 2007 to develop ring-roads, bypasses and flyovers to avoid
traffic bottlenecks on selected stretches at a cost of Rs. 16680 crores.
31

32. 3. I.R.C. (Indian Road Congress)
I.R.C. was formed in 1934 by the Govt. of India to collect the ideas and expertise for the planning and
development of roads in the country to meet the demand of vehicular traffic. I.R.C. was given the
responsibility of formulating standards and specifications of different types of roads for their
construction and maintenance. I.R.C. publishes journals, research papers and standard specifications
for different roads.
Objectives of I.R.C.:
1. To promote and encourage the science and practice of construction and maintenance of roads.
2. To promote the use of standard specifications and to formulate new specifications.
3. To hold periodical meetings to discuss the technical questions regarding roads.
4. To suggest legislation for the development, improvement and protection of roads.
5. To suggest new methods of construction, administration, planning, designing, testing of
materials and maintenance.
6. To reduce the number of accidents.
7. To ensure overall safety.
8. To reduce travel cost and time. 32

33. 4. MSRDC (Maharashtra State Road Development Corporation)
MSRDC is a corporation established and fully owned by the Government of Maharashtra. MSRDC mainly
deals with the properties and assets comprising movables and immovables including land, road projects,
flyover projects, toll collection rights. The main objectives of MSRDC are as follows;
» To improve and develop integrated transport infrastructure such as roads, expressways, bridges, flyovers,
ports, rail projects, airports, etc.
» To raise resources for the identified projects.
» To follow transparent and competitive bidding procedures to ensure quality works at the most economic
cost.
» To encourage private sector participation in transport infrastructure.
Major functions of the Corporation are,
» to promote and operate - road projects
» to plan, investigate, design, construct and manage identified road projects and their area development.
» to enter into a contract in respects of the works and any other matters transferred to the Corporation
along with assets and liabilities.
» to invite tenders, bids, offers and enter into contracts for the purposes of all the activities of
the corporation.
» to promote participation of any person or body or association of individuals, whether incorporated or
33

34. 34
5. Pradhan Mantri Gram Sadak Yojana (PMGSY)
An accelerated village road village road development called Pradhan Mantri Gram Sadak Yojana was launched by
the Govt. of India in Dec 2000 under the guidance of Ex. Prime Minister Shri Atal Bihari Vajapayee to provide
villages with all-weather roads.
The ministry of Rural Development was given the responsibility to prepare the master plans in consultation with the
State Governments.
The objective of PMGSY was to provide connectivity to all unconnected habitations having a population of 500 and
above with all-weather roads.
The above population limit is relaxed in the case of hills, tribal and desert areas of the country.
The Pradhan Mantri Gram Sadak Yojana (PMGSY) is a 100% Centrally Sponsored Scheme. 0.75₹/ litre out of the
Cess on High Speed Diesel (HSD) is earmarked for this Programme.
Programme Objectives
1) The primary objective of the PMGSY is to provide Connectivity, by way of an All-weather Road (with necessary
culverts and cross-drainage structures, which is operable throughout the year), to the eligible unconnected
Habitations in the rural areas with a population of 500 persons and above in Plain areas.
2) In respect of the Hill States (North-East, Sikkim, Himachal Pradesh, Jammu & Kashmir and Uttarakhand), the
Desert Areas (as identified in the Desert Development Programme), the Tribal (Schedule V) areas and Selected
Tribal and Backward Districts (as identified by the Ministry of Home Affairs and Planning Commission).
3) The objective would be to connect eligible unconnected Habitations with a population of 250 persons and above

35. Classification of Roads
The classification of roads is mostly based on following conditions :
All-weather roads and
Fair-weather roads.
a) All-weather roads:
These roads are negotiable during all weather, except at major river crossings where interruption of traffic
is permissible up to a certain limit extent, the road pavement should be negotiable during all weathers.
b) Fair-weather roads:
On these roads, the traffic may be interrupted during monsoon season at causeways where streams may
overflow across the roads.
• Based on the Carriage Way
Paved Roads: These are the roads which have a hard pavement surface on the carriage way
Unpaved Roads: These are the roads without the hard pavement surface on the carriage way, usually they are
earthen or gravel roads.
35

36. 36
• Based on Surface Pavement Provided
1) Surface Roads:
These roads are provided with any type of bituminous or cement concrete surfacing.
2) Unsurfaced Roads:
These roads are not provided with a bituminous or cement concrete surfacing. Roads which are
provided with bituminous surfacing are called as Black Toped Roads and that of concrete are referred to
as Concrete Roads respectively.
b) Methods of Classification of Roads The roads are generally classified based on the following
1)Traffic Volume
2)Load transported of tonnage
3)Location and function
1) Based on Traffic Volume:
The classification based on traffic volume or tonnage have been arbitrarily fixed by different agencies and
are classified as
•Heavy
•Medium
•Light traffic roads
2) Based on Load transported or tonnage:
•Class-I or Class-A
•Class-II or Class-B.

37. 37
Types of Roads Vehicles Per Day
Very heavy traffic roads Above 600
Heavy traffic roads 251 to 600
Medium traffic roads 70 to 250
Light traffic roads Below 70
Classification of Roads According to Traffic :
Based on traffic volume the roads are classified as follows :
Classification of Roads According to Tonnage :
Based on total tonnage per day, the roads are classified as follows :
Types of Road Vehicles Per Day
Very heavy traffic roads Above 1524
Heavy traffic roads 1017 to 1524
Medium traffic roads 508 to 1017
Light traffic roads Below 508

38. 38
3) Based on location and Function:
The Nagpur Road Plan classified the roads in India into the following categories
National Highways (NH):
The NH connects the capital cities of the states and the capital cities to the port. The roads connecting the
neighboring countries are also called as NH. The NH are at least 2 lanes of traffic about 7.5m d wide. The NH are
having concrete or bituminous surfacing.
State Highways (SH):
SH are the main roads within the state and connect important towns and cities of state. The width of state highways is
generally 7.5m.
c) Major District Roads (MDR):
These roads connect the areas of production and markets with either a SH or railway. The MDR should have at least
metaled single lane carriage way (i.e., 3.8m) wide. The roads carry mixed traffic.
d) Other District Roads (ODR):
these roads connect the village to other village or the nearest district road, with ghat, river etc. these roads have a
single lane and carry mixed traffic.
e) Village Roads (VR):
these roads, like other district roads, connect the village or village or nearby district road. The roads carry mixed
traffic.

39. National Highways (NH)The main highways running through the length and breadth of India, joining
major parts, capital of states, large industrial and tourist centers, foreign highways including roads
required for strategic movements for the defence of India etc. are known as National Highways (NHs).
All the national highways are assigned with the respective numbers.
For example:
Amritsar- Ambala- Delhi Road- NH1
Delhi- Agra- Kanpur- Culcutta Road – NH2
Agra- Mumbai Road- NH3
Modural and Rameswaram- NH49
The responsibility of construction and maintenance of these roads lies with the central government.
Central Government holds the responsibility of construction and maintenance of these roads.
State Highways (SH) The highways linking up with the national highways of adjacent states,
district headquarters and important cities with the states are known as State Highways (SHs).
• The geometric design specifications and design speed for NH and SH are same. These highways serve as
arterial routes of traffic from district road within the state.
• The responsibility of construction and maintenance of these roads lies with state government. However,
the central government gives grant for development.
39

40. Major District Roads (MDR)
• The important roads within a district serving areas of production and markets and connecting these
places with each other or with the main highways are known as Major District Roads (MDRs).
• The responsibility of construction and maintenance of these roads lies with District Authorities.
However, the state government gives grant for development of these roads
Other District Roads (ODR) :
• The roads serving rural areas of production and providing them with outlet to
market centers, tahsil headquarters, block development headquarters, railway stations etc.
are known as Other District Roads (ODRs). This have lower design specification than MDR
Village Roads (VR) :
• The roads connecting villages or group of villages with each other or with the nearest road of
higher category are known as village roads.
• These roads are very important from the rural area development point of view. They are generally
un-metalled with single lane width of stabilized soil or gravel. The responsibility of construction
and maintenance of these roads lies with the local district authorities.
40

41. 41
Classification of Urban Roads
The road system within urban areas are classified as Urban Roads and will form a separate category of roads taken
care by respective urban authorities.
The lengths of urban roads are not included in the targets of the 3rd 20-year road development plan 1981-2001.
a) Arterial roads
b) Sub-arterial roads
c) Collector Streets
d) Local Streets
Arterial and Sub-arterial roads are primarily for through traffic on a continuous route, but sub-arterials have a lower
level of traffic mobility than the arterials.
Collector streets provide access to arterial streets and they collect and distribute traffic from and to local streets
which provide access to abutting property.
Road Patterns
There are various types of road patterns and each pattern has its own advantages and limitations. The choice of the
road pattern depends upon the various factors such as:
Locality
Layout of the different towns, villages, industrial and production centers.
Planning Engineer.
The various road patterns may be classified as follows:

42. Types of Road Patterns
42
When the road is constructed in
patterns like rectangular, radial,
hexagonal, etc for the proper
management of traffic and also to
interconnect the branch roads with
main roads then it is called road
pattern.
The main principle of road patterns is
to reduce the time and distance that
the vehicle takes to reach the
destination place. It also focuses on
the interconnection of branch roads.

43. Rectangular or Block Pattern
43
a. In this pattern; the whole area is divided into rectangular blocks.
b. Streets or branch roads intersect with each other at the right
angle.
c. The main roads always pass through the centre and it should be
wide enough.
d. Branch roads may be narrow as compared to main roads.
e. The main roads should be provided with a direct approach to
outside the city.
Advantages
~ The rectangular blocks can be further fractioned into small rectangles that may be used for the
construction of buildings placed back to back, having roads on their front.
~ It is widely adopted on city roads.
~ Construction and Maintenance is quite easy.
Disadvantages
~ It is not convenient because roads are perpendicular to each other. This increases the rate of
accidents due to poor visibility at a perpendicular junction.

44. Radial or Star and Block Pattern
44
a. It is a combination of star and block patterns.
b. The entire area is divided into a radial network of roads
radiating from the centre outwardly with a block pattern
network of roads in between the radial main streets.
Advantages
~ Less risky as compared to the rectangular pattern.
~ It reduces the level of congestion at the primary bottleneck
location.
~ If one radial road is blocked then another can be used as an
alternative.
Disadvantage
~ It is only effective when two-lane ramp traffic does not have to
merge at the downstream end of the ramp.

45. Radial or Star and Circular Pattern
45
It is the pattern in which the main roads(radial roads) radiates from the
central point and are connected with concentric roads(ring roads) that
are also radiating outwardly.
Advantages
~ It is safe as compared to the above patterns because vehicles travel in the
same direction.
~ Roundabouts present in this pattern improves the efficiency of traffic
flow. This also reduces fuel consumption and emissions of the vehicle.
~ Using a circular pattern in place of traffic signals reduces the possibility
of rear-end crashes.
Disadvantages
~ Providing a good curve during the implementation of this pattern is
quite challenging.
~ There is necessary proper provision of the traffic signal, road markings
and lighting to alert the drivers that they are approaching a roundabout.

46. Radial or Star and Grid Pattern
46
a. This pattern is formed by the combination of Star and Grid
Pattern.
b. As in other, a radial network of road radiates from the centre
outwardly. Then, the main radial streets are interconnected by
providing a grid pattern.
Advantages
~ It increases the efficiency of land usage and unit density.
~ It improves the traffic flow in both directions utilizing
Savannah’s cellular structure.
~ It provides high safety to vehicular traffic with a high
proportion of 3-way intersections.
Disadvantages
~ Splitter islands should be extended far enough.
~ High construction cost because of the need for extra traffic
signals, road marking and lighting.

47. 47
Hexagonal Pattern
47
a. In this, the entire area is divided into hexagonal
patterns.
b. Three roads meet the built-up area boundary by the
sides of the hexagons at every corner of the hexagon
which can be further divided into suitable sizes.

48. 48
Planning Surveys
The studies for collecting the factual data for highway planning are known as ‘Fact Finding Studies’ or ‘Planning
Surveys’.
The fact-finding studies point to an intelligent approach for planning and these studies should be carried if the
highway programme is to be protected from inconsistent and short-sighted policies.
Planning based on the factual data and analysis may be considered scientific and sound.
Objectives of Planning Surveys:
Workout, the financial system and recommended changes in tax arrangements and budget procedures, provide
efficient, safe economics, comfortable and speedy movement for goods and people.
Plan a road network for efficient traffic operation at minimum cost.
Plan for future requirements and improvements of roads in view of developments and social needs.
Fix up data wise priorities for development of each road link based on their utilities.
The planning surveys consist of the following studies:
Economic Studies:
The details to be collected during the economic studies are useful in estimation of the requirements, cost involved for
the proposed highway improvement programme and economic justification.
This study consists the following details:
Population and its distribution
Trend of population growth
Age and land products
Existing facilities
Per Capita income

49. 49
b) Financial Studies
The financial studies are essential to study the various financial aspects such as sources of income, various types of
revenues from duties and taxes on products, road transport, vehicle registration, court fees etc. and the future trends.
This study involves collecting the details such as:
Sources of income
Living Standards
Resources from local levels
Factor trends in financial.
c) Traffic or Road Use Studies
All the details of the existing traffic, such as classified traffic volume, growth rate of different vehicle classes, pattern
of flow or origin destination characteristics, particulars of passenger trips and goods movements, existing facilities for
mass transportation, trend in road accidents, accidents costs etc.
The detail collected are as follows
Classified traffic volume in vehicles per day, annual average daily traffic, peak and design hourly volume
Origin and destination studies based on home interview method
Traffic flow pattern
Mass transportation facilities
Accidents, their causes and cost analysis
Future trend and growth in traffic volume and goods traffic, trend in traffic pattern
Growth of passenger trips and the trend in the choice of modes

50. 50
d) Engineering Studies
All the details of the topography, soil and drainage characteristics, alignment of the existing roads, deficiencies in
drainage, alignments and geometrics of existing roads and requirements of essential upgradation, identification of
maintenance and problems etc.,
This involves:
Topographic study and Soil details
Location and classification of existing roads
Assessment of various other developments in the area that are likely due to the proposed highway development
Road life studies
Specific problems in drainage constructions and maintenance.
Preparation of Plans
The details collected during the planning surveys are tabulated and plotted on the maps of the area under planning.
Before finalizing the alignment and other details of the road development program, the information collected during
the fact-finding studies are presented in the form of various plans.
They are as follows
Plan-1: General area plan showing most of the existing details about the topographical details related to existing road
network, drainage, structures, towns and villages with population, agricultural, industrial and commercial activities.
Plan-2: Plan showing the distribution of population groups in accordance with the categories made in appropriate
plan.
Plan-3: Plan showing the locations of places with their respective quantities of productivity.
Plan-4: Should indicate the existing network of roads and proposals received. Ultimately, the Master plan is the one to
be implemented.

51. 51
Master Plan
Master plan is referred to as road development plan of a city; district or a street or for whole country.
It is an ideal plan showing full development of the area at some future date.
It serves as the guide for the plan to improve some of the existing roads and to plan the network of new roads.
It helps in controlling the industrial, commercial and agricultural and habitat growth in a systematic way of that
area.
It gives a perceptive picture of a fully developed area in a plan and scientific way.
Stages in the preparation of master plan:
Data Collection: It includes data regarding existing land use, industrial and agricultural growth, population, traffic
flow, topography, future trends.
Preparation of draft plan and invite suggestions and comments from public
Revision of draft plan in view of the discussions and comments from experts and public.
Comparison of various alternate proposals of road system and finding out the sequence in which the master plan will
be implemented.
In India, targeted road lengths were fixed in various road plans, based on population, area and agricultural and
industrial products.
The same way it may be taken as a guide to decide the total length of road system in each alternate proposal while
preparing a master plan for a town or locality.

52. 52
Saturation System
In this system optimum road length is calculated for an area based on the concept of attaining maximum utility per
unit length of the road. This is also called as Maximum Utility System.
Factors to attain maximum utility per unit length are:
1. Population served by the road network ,2. Productivity served by the network ,3. Agricultural Products ,
4. Industrial Products
The various steps to be taken to obtain maximum utility per unit length are:
Population factors or units:
Since, the area under consideration consists of villages and towns with different population these are grouped into
some convenient population range and some reasoning values of utility units to each range of population serve are
assigned.
Population less than 500, utility unit = 0.25
501 to 1001, utility unit = 0.50
1001 to 2000, utility unit = 1.00
2001 to 5000, utility unit = 2.00 etc.
2) Productivity Factors or units:
The total agricultural and industrial products served by each road system are worked out and the productivity served
may be assigned appropriate values of utility units per unit weight.
3) Optimum Road length:
Based on the master plan the targeted road length is fixed for the country on the basis of area or population and
production or both. And the same may be taken as a guide to decide the total length of the road system in each
proposal.

53. 53
Terrain Classification
The geometric design should be according to the nature of the terrain for economy. IRC has classified the terrain
as per the general slope of the country.
% cross slope of the country Classification
0 – 10 Plain
10 – 25 Rolling
25 – 60 Mountainous
More than 60 Steep
Design Speed
The maximum speed at which vehicles can continuously travel safely under favorable conditions is known as
design speed. The factors governing the design speed are sight distances, gradients and curvatures.
In India, different speed standards have been assigned depending upon the importance or the class of the road such
as National/State Highways, Major/Other District Roads and Village Roads. Further the design speed standards are
modified depending upon the terrain or topography.

54. 54
Sr.No
.
Road
classification
Ruling Design speed km/hr
Plain
terrain
Rolling
terrain
Mountainous
terrain
Steep
terrain
1 Expressways 120 100 80 80
2 N.H. and S.H. 100 80 50 40
3 M.D.R. 80 65 40 30
4 O.D.R. 65 50 30 25
5 V.R. 50 40 25 25
Standard design speeds according to IRC

55. Vehicular Characteristics
The various Vehicular Characteristics affecting the road design can be classified as
Static/Physical Characteristics
Dynamic Characteristics
a) Static/Physical Characteristics
• Axle Load: Weight of vehicle affects
Structural design of pavement (number of layers,
thickness of each layer, material requirements etc)
and bridge/fly-over/grade separator
• Width: Width of vehicle affects
Lane width - Shoulder width - Width of parking
bay
• Length: Length of vehicle affects
-Design of horizontal alignment - Passing sight
distance – Parking facilities
• Height: Height of vehicle affects
-Clearance to be provided under the
structures e.g. under-bridge, over-bridge etc
b) Dynamic Characteristics
• Speed
-Horizontal and vertical alignment design
-Limiting radius
-Grade and Superelevation
-Stopping/overtaking sight distance
-Intersection design and control
• Acceleration/Deceleration (braking)
performance
-Acceleration capability influences junction
capacity, safe passing distance etc
-Maximum deceleration rate is required to know
safe stopping distance
55

56. 56
Cross-sectional elements of a road
Road in cutting
Road in embankment

57. A road partially in cutting & embankament
57

58. 58

59. 59
1.Road land width/ Right of way –
It is the area of land acquired for the road along its
alignment.
Road land width/ Right of way according to IRC
Sr.
No.
Road classification
Plain &
Rolling terrain
(metre)
Mountainous &
Steep terrain
(metre)
1 Expressways 90 60
2 N.H. and S.H. 45 24
3 M.D.R. 25 18
4 O.D.R. 15 15
5 V.R. 12 9
Sr.
No.
Road
classification
Roadway width in metre
Plain &
Rolling
terrain
Mountainous & Steep
terrain
1 NH and SH
Single lane 12 6.25
Two lanes 12 8.80
2 MDR
Single lane 9 4.75
Two lanes 9 -
3 ODR
Single lane 7.5 4.75
Two lanes 9 -
4 VR (Single lane) 7.5 4
2. Roadway width
The roadway width is the total width of
carriageway with the shoulders on either side.

60. 60
Road Margins
These are the portions of land width on either side of the roadway. These margins are used for
parking lane, frontage road, driveway, footpath, side drains and side slopes.
Shoulders
Shoulders are the strips provided on either side of the carriageway having enough strength to
support a loaded truck in wet weather. Shoulders provide space for break-down vehicles. Shoulders
are given outward slopes to drain off the rain water quickly.
The minimum shoulder width recommended by IRC is 2.5 m
Side slopes
The slopes given to the sides of earthwork of a road for its stability are called side slopes.
Generally, 2:1 slope
Berms
Berms prevent side slopes of the road embankment from damage by erosion or the cutting from
damage by lateral thrust due to the spoil banks.

61. Carriageway (Pavement)
61
Sr.No. Number of lanes Width of Carriageway (m)
1 Single lane 3.75
2 Two lanes without raised kerbs 7.00
3 Two lanes with raised kerbs 7.50
4 Width per lane for multi-lane pavements 3.50
5 Multi-lane pavements 3.50 per lane
The portion of roadway constructed for movement of vehicular traffic is called
carriageway or pavement.
IRC recommendations:
On local streets of residential area the carriageway width may be limited to 3 m.

62. Kerbs
62
Kerbs are provided longitudinally on either side of the
carriageway to guide traffic.
Types of Kerbs:
• Mountable Kerbs: It is possible to ride over the kerbs or enter
the shoulder in case of any emergency.
• Low-speed barrier Kerbs: These are used as barriers to
restrict entry of slow-moving vehicles on footpaths. Crossing
over these kerbs may cause severe damage to the vehicles.
• High-speed barrier Kerbs: These are used in exceptionally
dangerous locations like hill roads and bridges to prevent the
vehicles from leaving the road under any circumstances.

63. Types of kerb
63

64. Camber
64
Camber or cross-slope is the slope provided to the road
surface in the transverse direction to drain off the rain
water from the road surface.
Camber is defined as the slope of the line joining the
crown and the edge of the road surface. A camber of 1
in 30 means that for a 30 m wide road, the crown of the
road will be 0.50 m above the edge of the road.
Camber is designated by 1in n i.e. 1 vertical to n
horizontal. Camber is also expressed in percentage. If
camber is x%, then the slope is x in 100.

65. 65
Sr.No. Type of road surface Camber in areas of
Heavy rain fall Low rain fall
1 Cement concrete roads and
high type bituminous
surfacing
1 in 50 (2%) 1 in 60
(1.7%)
2 Thin bituminous surfacing 1 in 40
(2.5%)
1 in 50 (2%)
3 Water Bound Macadam 1 in 33 (3%) 1 in 40
(2.5%)
4 Earthen roads 1 in 25 (4%) 1 in 33 (3%)
IRC recommendations for camber:
The amount of camber depends on the intensity of rainfall and the permeability of the road
surfacing material.
The water should drain off quickly,
•To prevent entry of surface water into the subgrade soil through pavement. If the water enters into
the subgrade, the stability and life of the pavement gets adversely affected.
To allow the pavement to get dry soon after the rain so that it should not become slippery and
unsafe for the vehicles.

66. Sight distance
66
The safe and efficient operation of vehicles on the road depends very much on the visibility of the road ahead of the
driver. Thus the geometric design of the road should be done such that any obstruction on the road length could be
visible to the driver from some distance ahead . This distance is said to be the sight distance.
Types of sight distance
Sight distance available from a point is the actual distance along the road surface, over which a driver from a
specified height above the carriage way has visibility of stationary or moving objects. Three sight distance situations
are considered for design:
• Stopping sight distance (SSD) or the absolute minimum sight distance
• Intermediate sight distance (ISD) is defined as twice SSD
• Overtaking sight distance (OSD) for safe overtaking operation
• Head light sight distance is the distance visible to a driver during night driving under the illumination of head lights
• Safe sight distance to enter into an intersiection.

67. 67
The most important consideration in all these is that at all times the driver traveling at the design speed of the
highway must have sufficient carriageway distance within his line of vision to allow him to stop his vehicle before
colliding with a slowly moving or stationary object appearing suddenly in his own traffic lane. The computation of
sight distance depends on:
• Reaction time of the driver
Reaction time of a driver is the time taken from the instant the object is visible to the driver to the instant when the
brakes are applied. The total reaction time may be split up into four components based on PIEV theory. In practice,
all these times are usually combined into a total perception-reaction time suitable for design purposes as well as for
easy measurement. Many of the studies shows that drivers require about 1.5 to 2 secs under normal conditions.
However, taking into consideration the variability of driver characteristics, a higher value is normally used in
design. For example, IRC suggests a reaction time of 2.5 secs.
• Speed of the vehicle
The speed of the vehicle very much affects the sight distance. Higher the speed, more time will be required to stop
the vehicle. Hence it is evident that, as the speed increases, sight distance also increases.

68. 68
• Efficiency of brakes
The efficiency of the brakes depends upon the age of the vehicle, vehicle characteristics etc. If the brake efficiency
is 100%, the vehicle will stop the moment the brakes are applied. But practically, it is not possible to achieve 100%
brake efficiency. Therefore the sight distance required will be more when the efficiency of brakes are less. Also for
safe geometric design, we assume that the vehicles have only 50% brake efficiency.
• Frictional resistance between the tyre and the road
The frictional resistance between the tyre and road plays an important role to bring the vehicle to stop. When the
frictional resistance is more, the vehicles stop immediately. Thus sight required will be less. No separate provision
for brake efficiency is provided while computing the sight distance. This is taken into account along with the factor
of longitudinal friction. IRC has specified the value of longitudinal friction in between 0.35 to 0.4.
• Gradient of the road
Gradient of the road also affects the sight distance. While climbing up a gradient, the vehicle can stop immediately.
Therefore sight distance required is less. While descending a gradient, gravity also comes into action and more time
will be required to stop the vehicle. Sight distance required will be more in this case

69. 69
Sight Distance and Importance:
Sight distance is the length of road visible ahead of the driver at any instance.
Sight distance available at any location of the carriageway is the actual distance a driver with his eye level at a
specified height above the pavement surface has visibility of any stationary or moving object of specified height
which is on the carriageway ahead.
The sight distance between the driver and the object is measured along the road surface.
Restrictions to Sight Distance
Restrictions to visibility or sight distance may be caused in the following circumstances.
At horizontal curves, when the line of sight is obstructed by objects at the inner side of the curve. Here the sight
distance is measured along the centre line of the horizontal curve when the vehicle driver is able to see another
vehicle or object on the carriageway
At a vertical curve, the line of sight is obstructed by the road surface of the summit curve (i.e., a vertical curve of the
road with convexity upwards).
In this case also the sight distance is measured along the centre line of the vertical curve when the vehicle driver is
able to see another vehicle or object on the road
At an uncontrolled intersection when a driver from one of the approach roads is able to sight a vehicle from another
approach road proceeding towards the intersection, Here the sight distance for each vehicle driver is the distance
from the position when the two can see each other up to the intersection point of the two roads.

70. 70

71. 71
1.Stopping Sight Distance (SSD)
Factors on which visibility or sight distance depends
o The minimum distance visible to a driver ahead or the sight distance available on a highway at any spot should
be of sufficient length to safely stop a vehicle travelling at design speed, without collision with any other
obstruction.
o Therefore, this Stopping Sight Distance (SSD) is also called Absolute Minimum Sight Distance. This is also
sometimes called Non-Passing Sight Distance.
o The sight distance available to a driver travelling on a road at any instance depends on the following factors:
• Features of the road ahead
• Height of the driver's eye above the road surface
• Height of the object above the road surface IRC has suggested the height of eye level of driver as 1.2 m and the
height of the object as 0.15 m above the road surface.
o Factors on which stopping distance depends The distance within which a motor vehicle can be stopped depends
upon the factors listed below:
a)Total reaction time of the driver
b)Speed of vehicle
c)Efficiency of Brakes
d)Frictional Resistance between the road and the tyre.
e) Gradient of the road, if any.

72. 72
a) Total reaction time of the driver
Reaction time of the driver is the time taken from the instant the object is visible to the driver to the instant the brakes
are effectively applied.
The actual time gap or the reaction time of the driver depends on several factors.
During this period of time the vehicle travels a certain distance at the original speed, which may be assumed to be the
design speed of the road.
Thus, the stopping distance increases with increase reaction time of the driver.
The total reaction time (t) may be split up into two parts
Perception Time
It is the time required for a driver to realise that brakes must be applied.
It is the time from the instant the object comes on the line of sight of the driver to the instant he realises that the
vehicle needs to be stopped.
•The perception time varies from driver to driver and also depends on several other factors such as the distance of
object and other environmental conditions.
oBrake Reaction Time
•It is also depending on several factors including the skill of the driver, the type of the problems and various other
environmental factors.
•The total reaction time may be explained with the help of PIEV theory.

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PIEV Theory
•According to PIEV theory, the total reaction time of the driver is split into four parts, viz., time taken by the driver
for
1)Perception :
Time to send sensation from Eye to Brain
2) Intellection
Time to rearrange different thoughts analysis
the situation by brain.
3) Emotion
Time elapsed in Emotional sensation.
4) Volition
Time for final decision.
•The PIEV time of a driver also depends on several factors such as physical and psychological characteristics of the
driver, type of the problem involved, environmental conditions and temporary factors.
1.Speed of vehicle
The stopping distance depends very much on the speed of the vehicle. First, during the total reaction time of the
driver the distance moved by the vehicle will depend on the speed. Second, the braking distance or the distance moved
by the vehicle after applying the brakes, before coming to a stop depends also on the initial speed of the vehicle.

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2.Efficiency of brakes
The braking efficiency is said to be 100 percent if the wheels are fully locked preventing them
from rotating on application of the brakes. This will result in 100 percent skidding which is normally undesirable,
except in utmost emergency. Also skidding is considered to be dangerous, as it is not possible for the driver to
easily control a vehicle after it starts skidding.
d) Frictional resistance between road and tyres
The factional resistance developed between road and tyres depends upon the 'skid resistance' or the coefficient
of friction, between the road surface and the tyres of the vehicle.
Analysis of Stopping Distance
The stopping distance of a vehicle is the sum of
The distance travelled by the vehicle at uniform speed during the total reaction time, t which is known
as Lag Distance.
The distance travelled by the vehicle after the applications of the brakes, until the vehicles comes to a dead stop
which is known as Braking Distance.

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Lag Distance :
During the total reaction time, t seconds the vehicle may be assumed to move forward with a uniform speed at
which the vehicle has been moving and this speed may be taken as the design speed.
If ‘v’ is the design speed in m/sec and ‘t’ is the total reaction time of the driver in seconds, then
Lag Distance = v t
If the design speed is V kmph, then the lag distance =Vt x (1000/60x60 )
= 0.278 V t ≈ 0.28 V t in meters
IRC has recommended the value of reaction time t as 2.5 sec for calculation of Stopping Distance.
Braking Distance On Level Surface
The coefficient of friction f depends on several factors such as the type and condition of the pavement and the value
of f decreases with the increase in speed.
IRC has recommended a set of friction co efficient values for the determination of stopping sight distance.
The braking distance,
Where
l - braking distance, m ,v - speed of the vehicle, m/sec
f - design coefficient of friction, f (0.40 to 0.35) ,g – acceleration due to gravity – 9.8 m/sec2

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Overtaking Sight Distance (OSD)
Over Taking Requirement
If all the vehicles travel along a road at the design speed, then theoretically there should be no need for any
overtaking.
In fact, all vehicles do not move at the design speed as each driver is free to travel at lower speeds and this is
particularly true under Mixed Traffic conditions.
It is necessary for fast moving vehicle to overtake or pass the slow-moving traffic.
The minimum distance open to the vision of the driver of a vehicle intending to overtake slow vehicle ahead with
safety against the traffic of opposite direction is known as Minimum Overtaking Sight Distance (OSD) or Safe
Passing Sight Distance.
The OSD is the distance measured along the centre line of the road which a driver with his eye level at 1.2m above
the road surface can see the top of an object 1.2m above the road surface.

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Factor Affecting OSD
Speeds of
Overtaking Vehicle
Overtaken Vehicle
Vehicle coming from opposite direction
Distance between the overtaking and overtaken vehicles,
the minimum spacing between vehicles depends on the
speeds
Skill and reaction time of the driver
Rate of acceleration of overtaking vehicle.
Gradient of the road.
Analysis Of Osd On A 2 – Way Road:
Simple overtaking process on a 2 – lane highway with 2 –
way traffic movement
Vehicle A travelling at the design speed v m/sec or V kmph
desires to overtake another slow-moving vehicle B moving
at a speed of vb m/sec or Vb kmph.
The vehicle A has to accelerate, shift to the adjacent right-
side lane, complete the overtaking manoeuvre and return to
the left lane, before oncoming vehicle C approaches the
overtaking stretch.

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•The overtaking manoeuvre may be split up into 3 operations, thus dividing OSD into 3 parts d1, d2 and d3.
d1 is the distance (m) travelled by the overtaking vehicle A during the reaction time, t (secs) of the driver from
position A1 to A2 before starting to overtake the slow vehicle B.
d2 is the distance travelled (m) travelled by the vehicle A during the actual overtaking operation during T (secs) from
position A2 to A3
d3 is the distance (m) travelled by oncoming vehicle C during the actual overtaking operation of A during T (secs)
from position C1 to C2.
Thus, on a 2-lane road with 2-way traffic the OSD = d1 + d2 + d3 in meters.
Assumptions made in the analysis
Assumptions made to calculate the values of d1,d2 and d3 (m) are given below:
The overtaking vehicle A is forced to reduce its speed from the design speed v (m/sec) to Vb (m/sec) of the slow
vehicle B and move behind it, allowing a space s (m), till there is an opportunity for safe overtaking operation.
When the driver of vehicle A finds sufficient clear gap ahead, decides within a reaction time t (sec) to accelerate and
overtake the vehicle B, during which the vehicle A moves at speed vb (m/sec) through a distance d1 from position A1
to A2.
The vehicle A accelerates and overtakes the slow vehicle B within a distance d2 during the overtaking time, T (sec)
between the position A2 to A3.
The distance d2 is split up into three parts
Spacing, s (m) between A2 and B
Distance b (m) travelled by the slow vehicle B between B1 and B2 during the overtaking manoeuvre of A
Spacing (m) between B2 and A3

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•During this overtaking time T (sec), the vehicle C coming from opposite direction travels through a distance d3 from
position C1 to C2.
Determination of the components of OSD
From position A1 to A2, the distance, d1 (m) travelled by overtaking vehicle A, at the reduced speed vb (m/sec) during
the reaction time, t (sec) = vb t (m). The IRC suggests that this reaction time Y of the driver may be taken as 2.0 sec as
an average value, as the aim of the driver is only to find an opportunity to overtake.
Therefore d1 = 2vb
b) From position A2, the vehicle A starts accelerating, shifts to the adjoining lane, overtakes the vehicle B, and shifts
back to its original lane ahead of B in position A3 during the overtaking time, T (sec). The straight distance between
position A2 and A3 is taken as d2 (m), which is further split into three parts, viz.,
d2 = (s + b + s)
c) The minimum distance between position A2 and B1 may be taken as the minimum spacing s (m) between the two
vehicles while moving with the speed vb (m/sec). The minimum spacing between vehicles depends on their speed and
is given by empirical formula
s = (0.7 vb + 6)
d) Now the time T depends on speed of overtaken vehicle B and the average acceleration a (m/sec2 ) of overtaking
vehicle A. The overtaking time T (sec) may be calculated by equating the distance d2 to (vb T + ½ a T2 ) using the
general formula for the distance travelled by a uniformly accelerating body with initial speed vb m/sec and a is the
average acceleration during overtaking in m/sec2
d2 = (vb T + 2s)

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e) The distance travelled by vehicle C moving at design speed v (m/sec) during the overtaking operation of vehicle A
i.e. during time T (sec) is the distance d2 (m) between positions C1 to C2. Hence,
d3 = v T (m)
In m/sec units OSD = (d1 + d2 + d3) = (vb t + vb T + 2s + vT)
Here
vb = initial speed of overtaking vehicle, m/s
t = reaction time of driver = 2 sec
V = speed of overtaking vehicle or design speed, kmph
s = spacing of vehicles = (0.7 vb + 6)
a= average acceleration during overtaking, m/sec.
In kmph units OSD = 0.28 Vb t + 0.28 Vb T + 2s + 0.28 V T
Here
Vb = initial speed of overtaking vehicle, kmph
t = reaction time of driver = 2 sec
V = speed of overtaking vehicle or design speed, kmph
s = spacing of vehicles = (0.2 Vb + 6)
A = average acceleration during overtaking, kmph

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•In case the speed of overtaken vehicle (vb or Vb) is not given, the same may be assumed as 4.5 m/sec or 16 kmph
less than the design speed of the highway. Therefore,
vb = (v - 4.5) m/sec
Vb = (V - 16) kmph
where v is the design speed in m/sec
V is the design speed in kmph.
The acceleration of the overtaking vehicle varies depending on several factors such as the make and model of the
vehicle, its condition, load and the speed; actual acceleration also depends on the characteristics of the driver. The
average rate of acceleration during overtaking manoeuvre may be taken corresponding to the design speed.

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o Overtaking sight distance on two-lane highways for different speeds
o Criteria For Sight Distance Requirement On Highway:
Absolute Minimum Sight Distance
SSD for the design speed is the absolute mining sight distance and this should be made available all along the road
stretch irrespective of the category of road. If on any road stretch SSD is not available due to any reason such as
obstruction to vision, immediate steps should be taken to either remove the obstruction to the sight line or install
suitable regulatory signs to specify the speed limit along with appropriate warning signs.
Overtaking Sight Distance
It is desirable that adequate overtaking sight distance is available on most of the road stretches such that the vehicles
travelling at the design speed can overtake slow vehicles at the earliest opportunity.

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•On road stretches with two-way traffic movement, the minimum overtaking distance should be (d1 + d2 + d3) where
overtaking is not prohibited.
On divided highways and on roads with one way traffic regulation, the overtaking distance need be only (d1 + d2) as
no vehicle is expected from the opposite direction.
On divided highways with four or more lanes, it is not essential to provide the usual OSD; however, the sight distance
on any highway should be more than the SSD, which is the absolute minimum sight distance.
Overtaking Zones
It is desirable to construct highways in such a way that the length of road visible ahead at every point is sufficient for
safe overtaking.
This is seldom practicable and there may be stretches where the safe overtaking distance cannot be provided.
In such zones where overtaking or passing is not safe or is not possible, sign posts should be installed indicating No
Passing or Overtaking Prohibited before such restricted zones start.
However overtaking opportunity for vehicles moving at design speed should be given at as frequent intervals as
possible. These zones which are meant for overtaking are called Overtaking Zones.
The width of carriageway and the length of overtaking zone should sufficient for safe overtaking. Sign posts should be
installed at sufficient distance m advance to indicate the start of the overtaking zones, this distance may be equal to
(d1 + d2) for one-way roads
(d1 + d2 + d3) for two-way roads
The minimum length of overtaking zone = 3 (OSD)
The desirable length of overtaking zones = 5 (OSD)

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c) Intermediate Sight Distance
At stretches of the road where requires OSD cannot be provided, as far as possible intermediate Sight Distance ISD
equal to twice SSD may be provided.
The measurement of the ISD may be made assuming both the height of the eye level of the driver and the object to
be 1.2 metres above the road surface.
Therefore,
ISD = 2 SSD

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Sight Distance at Uncontrolled Intersections
It is important that on all approaches of intersecting roads, there is a clear view across the corners from a
sufficient distance so as to avoid collision of vehicles. This is all the more important at uncontrolled
intersections.
The sight line is obstructed by structures or other objects at the corners of the intersections. The area of
unobstructed sight formed by the lines of vision is called the sight triangle.
•The design of sight distance at intersections may be based on three possible conditions,
Enabling the approaching vehicle to change speed
Enabling approaching vehicle to stop
Enabling stopped vehicle to cross a main road
Enabling the approaching vehicle to change speed

87. Thanks…