This document provides an overview of transportation engineering and highway classification systems. It discusses the following key points in 3 sentences: The syllabus covers introduction to transportation engineering, classification of roads, geometric design of highways, and horizontal and vertical alignment design. Module 1 defines transportation engineering and its importance, and discusses the historical development of road construction including Roman, Macadam, and Telford constructions. Highway classification systems are described based on traffic volume, location and function, and as primary, secondary, and tertiary routes according to the Lucknow Road Plan.

1. SYLLABUS
Introduction to Transportation Engineering, Classification of roads,
Typical cross sections of roads in urban and rural area, Requirements and
factors controlling alignment of roads Introduction to geometric design
of highways, Design controls and criteria, Design of highway cross
section elements, Design of horizontal alignment - Stopping sight
distance, Overtaking sight distance, super elevation, transition curve,
length and shift of transition curve, extra widening. Vertical alignment
(introduction only)
MODULE1
Part1

2. Transportation engineering
• Transportation engineering is the application of technology and
scientific principles to the planning, functional design, operation
and management of facilities for any mode of transportation in
order to provide for the safe, efficient, rapid, comfortable,
convenient, economical, and environmentally compatible
movement of people and goods from one place to other.
MODULE 1

3. Introduction To Transporatation Engineering
(Read Chapter2:Highway Engineering-S K Khanna,CEG Justo and A
Veeraragavan: page 12-22)
HISTORICAL DEVELOPMENT OF ROAD CONSTRUCTION
1. Roman Roads - Roman's are the pioneers in road construction.
2. Tresaguet‟s Construction
3. Metcalf Construction
4. Telford (1757-1834) construction:
❖Sub grade is kept horizontal - subgrade drainage was not proper
❖Heavy foundation stones,
❖total thickness of the order of 35 cm at edge to 41cm center
3. Macadem construction: (1756-1856)
The importance of sub grade draining and compaction was
recognized
and cross slope of 1 in 36 was proposed from subgrade level itself.

4. Highway development in India

5. 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.
❖ Jayakar Committee submitted its report by the year 1928.
❖ The Central Road Fund was formed by the year 1929
❖ The semi-official technical body called the „Indian Roads Congress‟(IRC) was
formed in 1934
❖ The Central Road Research Institute(CRRI) was started in the year 1950.
❖ The IRC will prepare standard specifications and provide a platform for the
expression of professional opinion on matters relating to road engineering
including those of organization and administration.

6. Motor Vehicle Act
❖ In 1939 the Motor Vehicles Act was brought into effect by Government of
India to regulate the road traffic in the form of traffic laws, ordinances and
regulations.
Nagpur Road Conference and Plan
❖ A conference of the Chief Engineers of all the states and provinces was
convened in 1943 by the Government of India at Nagpur
❖ „First 20-year Road Development Plan‟ in India was finalised for the period
1943 to 1963 at the Nagpur Road Conference. Therefore this road
development plan is popularly known as „Nagpur Road Plan‟.
❖ Aimed at 16 km per 100 sq km area of the country
Central Road Research Institute
❖ In the year 1950, the Central Road Research Institute (CRRI) was started at
New Delhi for carrying out research pertaining to road technology.

7. National Highway Act
❖ In 1956 the „National Highway Act was passed in the county.
⚫ To declare certain selected highways as „National Highways‟, the
responsibility of development and maintenance of which to be with the
central government.
⚫ To enter into any land for carrying out surveys.
⚫ To acquire land and take possession of the development of the national
highway.
Second Twenty Year Road Development Plan,1961-81 ( Bombay road plan)
❖ The target road length at the end of this second 20-year road development
plan was almost double that of the Nagpur road plan target
❖ Aimed at 32 km per 100 sq km area of the country
Highway Research Board (1973)
❖ to give proper direction and guidance to road research activities in India.

8. Third twenty-year road development plan, 1981-2001 (Lucknow road plan)
❖ Aimed at 82 km per 100 sq km area of the country
National highway Authority of India(NHAI)
❖ Established in 1988, became operational only in 1995.
❖ Responsibility is to develop, maintain and operate the National Highways
❖ Under the control of Ministry of Road and Transport and Highways

9. National Highway Development Program(NHDP)
❖ Prime focus is on developing International standard roads with facilities
for uninterrupted flow of traffic with Enhanced safety features
❖ Phase-I of NHDP is called the „Golden Quadrilateral‟ of total length
5846 km connecting the four major metropolitan cities – Kolkata, Delhi,
Mumbai and Chennai.

10. ❖ phases III, IV and V - Further development of selected stretches of
national highways
❖ phase VI - Development of expressways
❖ phase VII - improvements of urban road networks
Pradhan Mantri Gram Sadak Yojana (PMGSY)
❖ An accelerated village road development programme by the central
government in December 2000 to provide village connectivity with the all-
weather road.
Road Development Plan: Vision 2021
❖ Fourth 20 year Road Development Plan, 2001 -2021 should have been
formulated and got approved well before the year 2000.
Rural Road Development Plan: Vision 2025
❖ A separate document, „Rural Road Development Plan Vision: 2025‟ has been
prepared for the 20 year period 2005 – 2025 at the initiative of the
Ministry of Rural Development, Government of India.

11. MODES OF TRANSPORTATION
Basic mode of transportation are
⚫Land
• Roadway
• Railway
⚫Water
⚫Air

12. MODES OF TRANSPORTATION
(Read Chapter1:Highway Engineering-S K Khanna,CEG Justo and A Veeraragavan: page 1-10)
• Highway
Car, Bus, Truck, non- motorized ..etc
• Railways
Passenger and Goods
• Airways
Aircraft and Helicopters
• Waterways
Ships, boats…
• Continuous Flow systems
Pipelines,belts,elevetor,ropeway…etc.
• Merits and Demerits: Based on accessibility, mobility, cost, tonnage..

13. Airways
• Fastest among all other modes
• More comfortable
• Time saving
• Uneconomical
Waterways
• slowest among all other modes
• It needs minimum energy to haul unit load through
unit distance.
• This can be possible between ports on the sea routes or
along the river
• economical

14. Railways
• The transportation along the railways track could be
advantageous by railways between the stations both for the
passengers and goods, particularly for long distance.
• It depends upon the road transport i.e. road could serve as a
feeder system.
• Energy require to haul a unit load through unit distance by the
railway is only ¼ to 1/5 of that required by road.
• Safety

15. Highways
• It gives the maximum service to one and all
• It gives maximum flexibility for travel with reference to
route, direction, time and speed of travel
• It provide door to door service
• Other modes are depend on it
• It requires small investment for the government
• Motor vehicles are cheaper than other carriers like rail
locomotive and wagons
• It saves the time for short distance
• High degree of accident dueto flexibility of movement

16. Classification of Highways
(Read Chapter2:Highway Engineering-S K Khanna,CEG Justo and A Veeraragavan: page 23-27)

17. Based on the Traffic Volume
Based on Load or Tonnage
⚫ 1. Class I roads
⚫ 2. Class II roads
⚫ 3. Class III roads
CIVIL ENGINEERING
Types of roads vehicles per day
Very heavy traffic roads above 600
Heavy traffic roads 251 – 600
Medium traffic roads 70 – 250
Light traffic roads below 70

18. Based on location and function ( Nagpur road plan )
⚫ National highway (NH)
⚫ State highway (SH)
⚫ Major district road (MDR)
⚫ Other district road (ODR)
⚫ Village road (VR)

20. Based on modified system of Highways
classification (Lucknow Road Plan)
• Primary
⚫Expressways
⚫National Highways(NH)
• Secondary
⚫State Highway(SH)
⚫ Major District Roads(MDR)
• Tertiary
⚫Other District roads(ODR)
⚫ Village Roads(VR)

21. Type of Road Connects Speed
Expressway major points of traffic generation
high speed
(120km/hr)
NH
Major ports, foreign highways, capital of large states and
large industrial and tourist centers including roads required
for strategic movements for the defense of India.
100km/hr
SH
NH of adjacent states, district head quarters and
important cities within the state.
80km/hr
MDR
Important roads with in a district serving areas of
production and markets, connecting those with each other or
with the major highways.
60-80km/hr
ODR
serving rural areas of production and providing them with
outlet to market centers or other important roads like MDR
or SH
50-60km/hr
VR
They are roads connecting villages or group of villages with
each other or to the nearest road of a higher category like
ODR or MDR.
40-50km/hr

22. Expressways
•Heavy traffic at high speed (120km/hr)
•Land Width (90m)
•Full access control
•Connects major points of traffic generation
•No slow moving traffic allowed
•No loading, unloading, parking.
The Mumbai-Pune Expressway as seen
from Khandala

23. National Highways
• NH are the main highways running through the length and breadth
of India, connecting major parts,foreign highways,capital of large
states and large industrial and tourist centres including roads
required for strategic movements for the defence of India.
• The national highways have a total length of 70,548 kms. Indian
highways cover 2% of the total road network of India and carry
40% of the total traffic.
• The highway connecting Delhi-Ambala-Amritsar is denoted as NH-
1, whereas a bifurcation of this highway beyond Jalandar to
Srinagar and Uri is denoted NH-1-A
• The longest highway in India is NH7 which stretches from Varansi
in Uttar Pradesh to Kanyakumari in the southern most point of
Indian mainland.

24. National Highways cont…
ms) connecting Delhi-
)
• The shortest highway is NH47A which stretches from
Ernakulam to Kochi and covers total length of 4 Kms.
• Golden Quadrilateral –(5,846 Km)
connecting Delhi- Kolkata-Chennai-
Mumbai
⚫NH-2 Delhi- Kol (1453 km)
⚫NH 4,7&46 Che-Mum (1290km
⚫NH5&6 Kol- Che (1684 m)
⚫NH 8 Del- Mum (1419 km)

25. State Highways
• They are the arterial roads of a state, connecting up with
the national highways of adjacent states, district head
quarters and important cities within the state.
• Total length of all SH in the country is 1,37,119 Kms.
• Speed 80 kmph

26. Major District Roads
• Important roads with in a district serving areas of
production and markets , connecting those with each
other or with the major highways.
• India has a total of 4,70,000 kms of MDR.
• Speed 60-80kmph

27. Other district roads
▪ Serving rural areas of production and providing them with
outlet to market centers or other important roads like MDR
or SH.
▪ Speed 50-60kmph
Village roads
• They are roads connecting villages or group of villages with
each other or to the nearest road of a higher category like
ODR or MDR.
• India has 26,50,000 kms of ODR+VR out of the total
33,15,231 kms of all type of roads.
• Speed-40-50kmph

28. Urban Road Classification
1. Arterial Roads
2. Sub Arterial
3. Collector
4. Local Street

29. Type
Design
Speed
Land width Specification
Arterial
Roads 80km/hr 50-60m
No frontage access, no standing vehicle, very little
cross traffic.
Divided roads with full or partial parking
Pedestrian allowed to walk only at intersection
Sub
Arterial
Roads
60km/hr 30-40m
Bus stops but no standing vehicle.
Less mobility than arterial.
Collector
Street
50km/hr 20-30m
Located in residential, business and industrial areas
Full access allowed.
Parking permitted.
Local
Street
30km/hr 10-20m
Primary access to residence, business or other
abutting property
Less volume of traffic at slow speed
Unrestricted parking, pedestrian movements. (with
frontage access, parked vehicle, bus stops and no
waiting restrictions)
Urban Road Classification

30. Cross section elements
1. Carriageway
2. Shoulder
3. Roadway width
4. Right of way
5. Building line
6. Control line
7. Median
8. Camber/ cross slope
9. Crown
10. Side slope
11. Kerb
12. Guard rail
13. Side drain
14. Other facilities

31. 1. Carriage way:
• It is the travel way which is used for movement of vehicle, it takes
the vehicular loading .
• It may be cement concrete road or bituminous pavement.
• Width of carriageway is determined on the basis of the width of
the vehicle and the minimum side clearance for safety.

32. Two lane two-way road
carriageway

35. WIDTH OF CARRIAGEWAY
SL. NO. Class of road Width of carriageway in ‘m’
1 Single lane 3.75
2 Two lane without raised kerbs 7.0
3 Two lane with raised kerbs 7.5
4 Intermediate lane 5.5
5 Multilane pavement 3.5/lane

36. 2. Shoulder
• It is provided along the road edge to serve as an emergency
lane/ service lane for vehicle.
• The minimum shoulder width of 4.6 m so that a truck
stationed at the side of the shoulder would have a clearance of
1.85m from the pavement edge.
• IRC recommended the minimum shoulder width is 2.5 m
• It should have sufficient load bearing capacity even in wet
weather.
• The surface of the shoulder will be rougher than the traffic
lanes so that vehicles are discouraged to use the shoulder as a
regular traffic.
• The colour should be different from that of the pavement so as
to be distinct.

38. shoulder

39. unTreated
shoulder
Treated
shoulder

40. 3. Width of the roadway or formation width:
• It is the sum of the width of the carriageway or pavement
including separators if any and the shoulders.
WIDTH OF ROADWAY OF VARIOUS CLASSES OF ROADS
SL. No. Road classification Roadway width
Plane and rolling
terrain
Mountainous and
steep
terrain
1 NH & SH
a) Single lane
b) two lane
12
12
6.25
8.80
2 MDR
a) Single lane
b) two lane
9
9
4.75
4.75
3 ODR
a) Single lane
b) two lane
7.5
9
4.75
4.75
4 Village roads-single lane 7.5 4

41. 4. Right of way:
• It is the total area of land acquired for the road along its
alignment.
• It depends on the importance of the road and possible
future development.
• It is desirable to acquire more width of land as the cost of
adjoining land invariably increases very much , soon after the
new highway is constructed.

44. 5. Building line:
• In order to reserve sufficient space for future development of roads, It is
desirable to control the building activities on either side of the road
boundary, beyond the land width acquired for the land.
• Building line refers to the front line up to which the building can lawfully
extend. it is also called as set- back or font building line.
• a minimum distance of this building line from the center line of the
accompanying road is laid down as the limit beyond which no construction is
allowed towards the road.

45. 6. Control lines:
• In addition to “building line”, it is desirable to control the nature of
building upto further “set back distance” .
• In case of a public building such as cinemas, a commercial concern,
factories, which attract a large number of vehicles, should be set back at
a further distance apart from the building line.
• The line which accounts for this extra margin is known as the control line,
generally, in the urban and industrial area, the distance of control line is
taken as one and a half from the center of the roadway.

49. 7. Traffic separators or median
• The main function is to prevent head on collision between the
vehicle moving in opposite direction.
• Channelize traffic into streams at intersection.
• Segregate slow traffic and to protect pedestrians.
• IRC recommends a minimum desirable width of 5 m and may be
reduce to 3 m where land is restricted.
• The minimum width of median in urban area is 1.2m.
Median

50. Median/
separator
4-lane divided carriage way or dual carriage way

51. 8. Cross slope or
camber
•It is the slope provided to the road surface in the transverse
direction to drain off the rain water from the road surface.
•To prevent the entry of surface water into the
❖ subgrade soil through pavement.
❖ bituminous pavement layer.
•To remove the rain water from the pavement surface
•It depends on the pavement surface and amount of rainfall.
CIVIL ENGINEERING

52. Shape of the cross slope:
Straight line
camber

53. Recommended values of camber for different types of road surface
Sl no. Type of road surface Range of camber in areas of rain
fall range
Heavy rain Light rain
1 Cement concrete and high type
bituminous pavement
1 in 50(2%) 1 in 60(1.7%)
2 Thin bituminous surface 1 in 40(2.5%) 1 in 50(2%)
3 Water bound macadam(WBM) and gravel
pavement
I in 33(3%) 1 in 40(2.5%)
4 Earth Road 1 in 25(4%) 1 in 33(3%)
CIVIL ENGINEERING
TRANSPORTATION ENGINEERING

54. CIVIL ENGINEERING
In a district where the rainfall is heavy, two types of road pavement are to be
constructed:
(a) Two-lane State Highway with bituminous concrete surface
(b)major district road of WBM pavement, 3.8 m wide. What should be the
height of the crown with respect to the edges in these two cases, assuming
straight line camber?
Question
Answer

55. • Too steep slope is not desirable because of the following reasons
• Uncomfortable side thrust and unequal wear of the tyres as well
as road surface.
• Discomfort when crossing the crown during over taking operataion
• Problem of toppling over highly laden bullock cart and truck.
• Tendency of most of vehicle travel along the centre line.

56. 9. Kerb:
• It indicates the boundary between the pavement and median or
footpath or island or shoulder.
• It is desirable to provide kerbs in urban areas.
• It is of three types
1-Low or mountable kerb:
• It allow the driver to enter the shoulder area with little
difficulty.
• The height of the this type of shoulder kerb is about 10 cm above
the pavement edge with slope to help the vehicle climb the kerb
easily.
CIVIL ENGINEERING

57. 2-Semi-barrier kerb
• It is provided on the periphery of a roadway where the
pedestrian traffic is high.
• Height of about 15 cm above the pavement edge with a batter
of 1:1 on the top 7.5 cm.
• It prevents the parking of vehicle but during emergency it is
possible to drive over this kerb with some difficulty.
3-Barrier type kerb:
• It is provided in built-up area adjacent to the foot paths with
considerable pedestrian traffic.
• The height of the kerb is about 20 cm above the pavement
edge with a steep batter of 1V:0.25H.

59. kerb

60. 10.Road margins
i) Parking lane:
• Provided on urban roads to allow kerb parking
• Only parallel parking -safer for moving vehicle.
• Sufficient width say 3m
ii) Lay byes:
• Provided near the public conveniences with guide map
to enable driver to stop clear off the carriageway.
• It has 3m width, 30m length with 15m end tapers
on both sides.
iii) Bus bays:
• Provided by recessing the kerb to avoid conflict with
moving traffic.
• Located at least 75m away from the intersection

61. Bus
bays

63. v) Frontage road:
• Provided to give access to properties along an
important highway with control access to
express way or free way
• Frontage road allow vehicles using parallel
secondary 2-way or 1 way roads to merge on to
major multiple lane road
vi) Cycle track:
• It provided in urban areas when the volume of cycle
traffic on the road is very high.
• A minimum width of 2m is provided for cycle track.
vii) Driveway:
• It connect the highway with commercial
establishment like fuel stations, service stations etc
• It should be located away from the intersection.
viii) Footpath/side walk:
• These are provided in urban areas when the vehicular
as well as pedestrian traffic are heavy.
• To protect the pedestrian and decrease accident.
• Minimum width of 1.5m is provided.

64. Frontage
road

65. Footpath
Cycle track

66. ix) Guard rail:
• It is provided at the edge of the
shoulder when the road is
constructed on a fill exceeds 3 m
height.
• It is also provided on horizontal
curve so as to provide a better night
visibility of the curves under the
head light of the vehicle.
CIVIL ENGINEERING

67. Guard rail

68. CROSS SECTIONS OF URBAN AND
RURAL ROADS
Read Chapter4:Highway Engineering-S K Khanna,CEG Justo and A Veeraragavan:
page 88-89)

72. HIGHWAY ALIGNMENT
(Read Chapter3:Highway Engineering-S K Khanna,CEG Justo and A Veeraragavan)

73. Highway alignment
• The position or lay out of centre line of the highway on the
ground is called the alignment.
• It may be horizontal or vertical
• Horizontal includes straight path, horizontal deviation and
curves.
• Vertical includes vertical curves, vertical gradient
• Due to improper alignment, the disadvantages are,
⚫Increase in construction cost
⚫Increase in maintenance cost
⚫Increase in vehicle operation cost
⚫Increase in accident cost

76. Requirements of highway alignment
Alignment
Short
Easy
Economical
Safe

77. Factors controlling alignment
⚫
Obligatory points
⚫ Traffic
⚫ Geometric design
⚫ Economics
⚫
Other considerations
Additional care on hill roads
⚫Stability
⚫Drainage
⚫Geometric standards of hill roads
⚫Resisting length

78. Obligatory points
• Obligatory points through which alignment is to pass. Eg:-bridge site, intermediate
town, Mountain pass etc
• Obligatory points through which alignment should not pass. Eg:-religious places,
costly structure, unsuitable land etc
Traffic
• origin and destination survey should be carried out in the area and the desire lines
be drawn showing the trend of traffic flow.
• New road to be aligned should keep in view the desired lines, traffic flow patterns
and future trends.
Geometric design
• Design factors such as gradient ,radius of curve and sight distance
• Gradient should be flat and less than the ruling gradient or design gradient.
• Avoid sudden changes in sight distance, sharp horizontal curves, road intersections
near bend
Economy
Alignment finalised based on total cost including initial cost, maintenance cost and
vehicle operation cost.
Other consideration
Drainage consideration, political consideration, Surface water level, high flood level,
Environmental consideration

79. 1. Obligatory points: Controlling points which governs the highway
alignment
▪ Obligatory points through which alignment is to pass
Examples:-bridge site, intermediate town , Mountain pass etc…
▪ Obligatory points through which alignment should not pass.
Examples:-religious places, costly structure, unsuitable land etc…
Marshy, peaty and water logged areas are generally unsuitable

81. 2. Traffic
⚫ origin and destination survey should be carried out in the area and
the desire lines be drawn showing the trend of traffic flow.
⚫ New road to be aligned should keep in view the desired lines, traffic flow
patterns and future trends.
3. Geometric design
▪ Design factors such as gradient ,radius of curve and sight distance also
govern the final alignment of the highway.
▪ Gradient should be flat and less than the ruling gradient or design
gradient.
▪ Avoid sudden changes in sight distance, especially near crossings
▪ Avoid sharp horizontal curves
▪ Avoid road intersections near bend

82. 4. Economy
• Alignment finalised based on total cost including initial cost,
maintenance cost and vehicle operation cost.
5. Other consideration
• Drainage consideration, political consideration
• Surface water level, high flood level
• Environmental consideration

83. Additional factors on hilly roads
Stability
• A common problem in hilly roads is land sliding
• The cutting and filling of the earth to construct the roads on hilly
sides causes steepening of existing slope and affect its stability.
Drainage
• Avoid the cross drainage structure
• The number of cross drainage structure should be minimum.
Geometric standard of hilly road
• Gradient, curve and speed
• Sight distance, radius of curve
Resisting length
• The total work to be done to move the loads along the route taking
horizontal length, the actual difference in level between two stations
and the sum of the ineffective rise and fall in excess of floating
gradient. Should kept as low as possible.

84. Engineering Surveys for Highway alignment
Map study (Provisional
alignment Identification)
Reconnaissance survey
Preliminary survey
Final location and
detailed surveys

85. Highway Geometric Design
(Read Chapter4:Highway Engineering-S K Khanna,CEG Justo and A Veeraragavan)

86. Highway Geometric Design
⚫Cross section elements
⚫Sight distance considerations
⚫Horizontal alignment details
⚫Vertical alignment details
⚫Intersection elements
Design Controls and criteria
✔Design speed
✔Topography
✔Traffic factors
✔Design hourly volume and
capacity
✔Environmental and other
factors
CIVIL ENGINEERING
TRANSPORTATION ENGINEERING

87. Importance of geometric design
• The geometric design of a highway deals with the dimensions
and layout of visible features of the highway such as alignment,
sight distance and intersection.
• The main objective of highway design is to provide optimum
efficiency in traffic operation with maximum safety at reasonable
cost.
• Geometric design of highways deals with following elements :
⚫Cross section elements: pavement width, formation width, surface
characteristics and Cross slope
⚫Sight distance considerations
⚫Horizontal alignment details
⚫Vertical alignment details
⚫Intersection elements

88. Design Controls and criteria
•Design speed
•Topography
•Traffic factors
•Design hourly volume and capacity
•Environmental and other factors

89. 2. Topography
• Classified based on the general slope of the country.
⚫Plane terrain- <10% - Design speed: 100 kmph
⚫Rolling terrain- 10-25% - Design speed: 80 kmph
⚫Mountainous terrain- 25-60% - Design speed: 50 kmph
⚫Steep terrain- >60

90. 1. HIGHWAY CROSS SECTIONAL ELEMENTS
1. Pavement surface characteristics
Pavement surface depend on the type of pavement which is decided
based on the,
• Availability of material
• Volume and composition of traffic
• Soil subgrade
• Climatic condition
• Construction facility
• Cost consideration
The important surface characteristics are:
I. Friction
II. Pavement unevenness
III.Light reflecting characteristics
IV. Drainage of surface water

91. I. FRICTION
• Skidding: when the path travelled along the road surface is
more than the circumferential movement of the wheels due to
their rotation🡪 slide without revolving wheels/partially revolve
• Longitudinal skidding & lateral skidding
• Slipping: when a wheel revolves more than the
corresponding longitudinal movement along the road.
Factors affecting the friction or skid resistance
• Types of pavement surface
• Roughness of pavement
• Condition of the pavement: wet or dry
• Type and condition of tyre
• Speed of the vehicle
• Brake efficiency
• Load and tyre pressure
• Temperature of tyre and pavement

92. ❖worn out tyres offer higher friction factor on dry pavement but new
tyre with good threds gives higher friction factor on wet pavement
❖ IRC recommended the longitudinal co- efficient of friction
varies 0.35 to 0.4 and lateral co-efficient of friction of 0.15

93. II. PAVEMENT UNEVENNESS
• Higher operating speed are possible on even surface than
uneven surface.
• It affects,
▪ Vehicle operation cost
▪ Comfort and safety
▪ Fuel consumption
▪ Wear and tear of tyres and other moving parts
• It is commonly measure by an equipment call “Bump
Integrator”
• Bump integrator is the cumulative measure of vertical
undulations of the pavement surface recorded per unit
horizontal length.
• < 150 cm/km for good pavement surface ;250 cm/km for a
speed of 100kmph and more than 350 cm/km considered very
unsatisfactory even at speed of 50 kmph.

94. Unevenness of pavement surface may be caused by
⚫ In adequate compaction of the fill, subgrade and
pavement layers.
⚫ Un-scientific construction practices including the use of
boulder stones and bricks as soiling course over loose
subgrade soil.
⚫ Use of inferior pavement material.
⚫ Improper surface and subsurface drainage.
⚫ Improper construction machinery.
⚫ Poor maintenance

96. III. Light reflecting characteristics
▪ Night visibility depends upon the colour and light reflecting
characteristics of the pavement surface.
▪ The glare caused by the reflection of head lights is considerably
high on wet pavement surface than on the dry pavement.
▪ Light coloured or white pavement surface give good visibility at
night particularly during rains; however white or light colour of
pavement surface may produces glare and eye strain during
bright sunlight.
▪ Black top pavement surface on the other hand provides very poor
visibility at nights, especially when the surface is wet.