lecture one

1. HIGHWAY ENGINEERING
Lecture one: introduction

2. A highway pavement is a structure consisting of superimposed
layers of processed materials above the natural soil sub-grade,
whose primary function is to distribute the applied vehicle
loads to the sub-grade.
The pavement structure should be able to provide; a surface of
acceptable riding quality, adequate skid resistance, favorable
light reflecting characteristics, low noise pollution.

3. Highway pavement
The ultimate aim is to ensure that the
transmitted stresses due to wheel load are
sufficiently reduced, so that they will not
exceed bearing capacity of the sub grade.
Two types of pavements are generally
recognized as serving this purpose, namely
flexible pavements and rigid pavements.

4. ⦿Types of Pavements:
◾ rigid pavement
◾ Flexible pavement.
RIGID: applied to wearing surfaces constructed of
Portland cement concrete.
A pavement constructed of concrete is assumed to
possess considerable flexural strength that will
permit it to act as a beam and allow it to bridge over
minor irregularities, which may occur in the base or
subgrade on which it rests; hence the term rigid.
A concrete base that supports a brick or block layer
might also be described as rigid.

5. ⦿Types of Pavements:
◾ On the other hand, a flexible pavement is a
structure that maintains intimate contact with and
distributes loads to the subgrade and depends on
aggregate interlock, particle friction and cohesion
for stability.
◾ Thus the classification of flexible pavements
includes primarily those pavements that are
composed of a series of granular layers topped by a
relatively thin – quality bituminous wearing course.
◾ Typically, the highest – quality materials are at or
near the surface.
◾ Definition of a Pavement?

6. ⦿ A pavement is a structure made up of carefully
selected and well proportioned materials in
different layers designed to tranfer loads
applied to the surface so that the underlying
subgrade is not overstressed.

8. Requirements of a pavement
An ideal pavement should meet the following requirements:
1. Sufficient thickness to distribute the wheel load stresses to a safe
value on the sub-grade soil,
2. Structurally strong to withstand all types of stresses imposed upon
it,
3. Adequate coefficient of friction to prevent skidding of vehicles,
4. Smooth surface to provide comfort to road users even at high
speed,
5. Produce least noise from moving vehicles,
6. Dust proof surface so that traffic safety is not impaired by reducing
visibility,
7. Impervious surface, so that sub-grade soil is well protected, and
8. Long design life with low maintenance cost.

9. ⦿Traffic
⦿soil and pavement materials
⦿Environment
⦿construction and maintenance
practice.

10. ⦿Traffic has a major effect on
pavement performance.
⦿Traffic characteristics that affect
performance are traffic load, traffic
volume, tyre pressure, and vehicle
speed.
◾Traffic load produces stresses and strains within the
pavement
gradually
structure
contribute
and the subgrade, which
to the development of
pavement distresses.
◾For example, heavier loads result
potential for fatigue cracking and rutting.
in higher

11. ◾Traffic volume affects pavement
performance since larger number of load
repetitions increases the chance for fatigue
cracking.
◾Higher tyre pressure produces higher stress
concentrations at the pavement surface that
could result in rutting and shoving in the
HMS layer.
◾Vehicle speed affects the rate of applying
the load. Since asphalt concrete is a visco-
elastic plastic material, its response is
affected by the rate of load application.

12. Slow or stationary vehicles have more
chances of developing rutting and
shoving than high-speed vehicles.
On the other hand, high travel speeds
cause more severe bouncing of
vehicles, and result in larger dynamic
loading and increased roughness.

13. ⦿Design Vehicle
◾Length – capacity of a lane
◾Width – overtaking and capacity
◾Height – clearance at bridges, overheads
etc
◾Weight – load to be imposed on to the
pavement

14. ⦿ Soil and pavement materials significantly
affect pavement performance.
⦿ High quality materials are needed to provide
good support to traffic loads under various
environmental conditions.
⦿ Important material properties include
mechanical properties such as elasticity,
visco-elasticity, plasticity, temperature
susceptibility, durability and aging
characteristics.
⦿These properties affect how the material
responds to traffic loads and environmental
conditions such as temperature, freeze thaw
effect, and rain.

15. ⦿Environmental conditions that affect
pavement performance include moisture,
temperature, and their interaction.
⦿For example, moisture may reduce subgrade
support and weakens various pavement layers.
⦿ High temperatures soften asphalt concrete
and could create rutting within the surface
layer.
⦿ Temperatures below freezing have a bad
effect on pavement performance, especially
cycles of freeze and thaw.

16. ⦿ poor construction procedure will almost always ensure poor
pavement performance.
⦿ For example, poor compaction of subgrade or any pavement
layer allows excessive further compaction by traffic, which
appears in the form of rutting and surface cracking.
⦿ Poor placement of HMA during construction may result in weak
transverse or longitudinal construction joints that are susceptible
to early cracking and deterioration.
⦿ Excessive air voids in the HMA layer due to poor compaction will
result in fast aging followed by cracking.
⦿ In contrast, too much compaction of HMA will result in too small
amount of air voids that could create rutting or bleeding.
⦿ Lack of smoothness of the pavement during construction
increases the dynamic impact of traffic, and consequently,
speeds up the rate of developing roughness during service.

17. ⦿ Design of flexible pavement entails two steps
◾Mix design
◾Structural design
⦿Mix design involves the determination of the
relative proportions o a mixture, while
structural design involves the determination
of the layer thicknesses for the components of
a pavement structure.
⦿In structural design of pavements, the
objective is to determine for the given set of
materials, the layer thicknesses required for
the pavement to serve.

18. ⦿AASHTO
⦿Road Notes developed by
TRL Method
⦿CBR method
⦿MoWT method
⦿etc

19. ⦿In put factors include:
◾Traffic
◾Material characteristics
◾Environmental
considerations
◾Costs to be involved

20. ⦿traffic is considered in
terms of axles.
⦿Types of axles include:
◾Singleaxles
S
in
g
lew
h
e
e
ls/ty
re
s D
u
a
lty
re
s

21. ◾Tandem axles
◾T
ridem / T
riple Axles
◾NB: If outside 45inches, they will become
single axles

22. ⦿Traffic is composed of very many types and levels of
axles;
⦿A standard axle is proposed to handle all traffic.
⦿ Standard axle is an 18kip (18,000 pound) single axle
load with dual tyres. (Not that 1kip = 4.4kN).
⦿All other axle loads are converted to the standard
using an equivalency factor known as the EALF
.

24. Flexible pavements

25. Flexible pavement
Flexible pavements will transmit wheel load stresses to the lower layers by
grain-to-grain transfer through the points of contact in the granular
structure (see Figure above). The wheel load acting on the pavement will be
distributed to a wider area, and the stress decreases with the depth.
Taking advantage of these stress distribution characteristic, flexible
pavements normally has many layers. Hence, the design of flexible pavement
uses the concept of layered system. Based on this, flexible pavement may be
constructed in a number of layers and the top layer has to be of best quality
to sustain maximum compressive stress, in addition to wear and tear.
The lower layers will experience lesser magnitude of stress and low quality
material can be used. Flexible pavements are constructed using bituminous
materials.

27. Types of Flexible Pavements
1. Conventional layered flexible pavement,
2. Full - depth asphalt pavement
3. Contained rock asphalt mat (CRAM).
Conventional flexible pavements are layered systems with high
quality expensive materials are placed in the top where stresses are
high,and low quality cheap materials are placed in lower layers.
Full - depth asphalt pavements are constructed by placing
bituminous layers directly on the soil sub grade. This is more
suitable when there is high traffic and local materials are not
available.

28. Types of Flexible Pavements
Contained rock asphalt mats are constructed by placing
dense/open graded aggregate layers in between two
asphalt layers. Modified dense graded asphalt concrete is
placed above the sub-grade will significantly reduce the
vertical compressive strain on soil sub-grade and protect
from surface water.

29. Layers of a flexible pavement
Surface course is the layer directly in contact with traffic
loads and generally contains superior quality materials.
They are usually constructed with dense graded asphalt
concrete (AC). The functions and requirements of this
layer are:

30. Functions of the surfacing course
It provides characteristics such as friction,
smoothness, drainage, etc. Also it will prevent
the entrance of excessive quantities of surface
water into the underlying base, sub-base and
sub-grade,
It must be tough to resist the distortion under
traffic and provide a smooth and skid- resistant
riding surface,
It must be water proof to protect the entire
base and sub-grade from the weakening effect
of water

31. Base course
The base course is the layer of material immediately
beneath the surface of binder course and it provides
additional load distribution and contributes to the sub-
surface drainage.
It may be composed of crushed stone, crushed slag, and
other untreated or stabilized materials.

32. Sub-Base course
The sub-base course is the layer of material beneath the
base course and the primary functions are;
1. To provide structural support
2. Improve drainage,
3. Reduce the intrusion of fines from the sub-grade in
the pavement structure
4. If the base course is open graded, then the sub-base
course with more fines can serve as a filler between
sub-grade and the base course.
A sub-base course is not always needed or used. For
example, a pavement constructed over a high quality,
sub-grade may not need the additional features offered
by a sub-base course. In such situations, sub-base course
may not be provided.

33. Sub-grade
The top soil or sub-grade is a layer of natural soil
prepared to receive the stresses from the layers above. It
is essential that at no time soil sub-grade is overstressed.
It should be compacted to the desirable density, near the
optimum moisture content.

34. Rigid pavements
@ Rigid
the
pavements ( concrete pavements), as
name implies,
stronger
are rigid and
than
considerably
in tension.
in compression
O n e of the main characteristics of rigid
thin
pavements
pavement
wider area
Localized
is
slab
due
low
that a relatively
distributes the load over a
to its high rigidity.
strength roadbed material
can be overcome due to this wider
distribution area.

35. RIGID PAVEMENTS
@ In concrete pavements, the strength of the
pavement
concrete
however,
is contributed mainly by the
slab, in flexible pavements;
successive layers of the pavement
contribute cumulatively.
Since the modulus of elasticity of the
concrete slab is much greater than that of
of
the
the
the
e This
foundation material, a major portion
load carrying capacity is derived from
slab itself.
has often been referred to as beam
action.

36. F
Jointed unreinforced concrete pavements (JUCP):
■ The pavement consists in a succession of cast in place
unreinforced concrete slabs separated by joints to prevent
expansion fram developing stresses and to control cracks.
■ The slabs are linked together by tie bars or dowels to transmit the
vertical stresses.
Jointed reinforced concrete pavements (JRCP):
■ The pavement consists in a succession of cast in place
reinforced concrete slabs separated by joints to control cracks.
■ The slabs are linked together by tie bars or dowels to transmit the
vertical stresses.
■ JRCP are used where a probability exists for transverse cracking
during pavement life due to such factors as soil
temperature/ moisture change stresses.
movement and/ or
■ The longitudinal reinforcement is the main reinforcement. A
transverse reinforcement though not absolutely necessary in most
cases is usually added to facilitate the placing of longitudinal
bars.
Types of rigid pavements

37. Continuously
(CRCP):
reinforced concrete pavements
■ Are used for rather highly trafficked roads where
a good level of comfort is expected.
■ The principal reinforcement , in the
bars
form of
prefabricated mesh or reinforcing installed
at mid-depth of the slab, is again the longitudinal
steel which is essentially continuous throughout
the length of the pavement.
■ This longitudinal reinforcement is used to control
cracks which form in the pavement due to
volume change in the concrete.
Types of rigid pavements

38. e Basically, the use of the different types of
rigid pavement is as follows:
■ JUCP is suitable for all levels of traffic,
whenever the risk of subgrade movement
is low and an uncont rolled cracking not
very prejudicial.
■ JRCP is suit able for all levels of traffic
is used when the risk of sett lement s of
and
the
subgrade can not be neglected.
■ CRCP shall basically be considered only for
rather high design traffic (>30 msa).
Types of rigid pavements

39. Rigid pavements

40. Concrete Slab
I
Subbase
Subgrade
Capping Layer
(it required)
Roadbed
(where no
embankment is
used)
Typical Rigid Pavement structure

41. Typical Rigid Pavement structure
@ The load bearing capacity of
the
the
design
soil
of
subgrade is not important in
concrete pavements.
@ The prime requirement is to provide a
foundation on which construction traffic can
operate without impairing the shape to
which the surface
trimmed.
@ The capping layer
of the foundation has been
consists of selected fill and
is provided in cases of low strength roadbed
material.
■ It protects the underlying subgrade fram construction traffic
loading and provides a stronger platform for the subbase layer,
which is placed on top of the capping layer.

42. Typical Rigid Pavement structure
Base courses are often called subbase courses
@
when used with rigid pavements.
These terms are often
it should be noted that
used interchangeably and
either of the terms refers
@
to a prepared layer of material immediately
between the concrete slab and subgrade.
e The base courses (sub-bases) are utilized under
these pavements for several reasons:
■ Control of pumping, at joints and slab edges.
■ Control of frost action
■ Drainage
■ Control of shrink and swell of the subgrade due to volume changes in road
bed soils susceptible to such phenomena
■ T
o expedite construction.
■ T
o provide a stable "working platform" for the construction equipment
■ T
o provide a uniform concrete slab support;

43. Typical Rigid Pavement structure
@If water accumulates in the
mud
heavy
pavement under
likely
a joint,
pumping
vehicles
next.
is to occur as
pass fram one slab to the
@If the subgrade soil is
to
not free
draining
subbase.
draining
through
it is necessary provide a
This subbase should be free
and should
shoulder.
continue
the road

44. Dowel bars:
■ Are load transfer devices. They transfer load
across transverse joints while checking on
movement of the slabs.
■ It is thus necessary that adequate load transfer
across joints limits slab deflections to reduce
faulting, spalling and corner breaks
■ S
ince they are load transfer devices, they must
be fairly heavy and spaced at close intervals to
provide resistance to bending, shear, and bearing
on the
■ Dowel
where
concrete.
bars
load
are use
d
at joints on long slabs or
transfer by "aggregate interlock" is
suspect. Joints without dowels are generally
satisfactory if the joint opening is 1 mm or less.
Reinforcement in rigid pavements

45. Tie Bars
■ Are used to tie adjacent slabs together along the
longitudinal joint tightly so that load transfer
across is ensured.
■ Tie-bars at longitudinal joints are provided to
hold these joints tight ly closed and therefore
perform a similar function to steel
between transverse joints.
■ The purpose of a tie-bar is to hold
reinforcement
a joint tightly
closed to allow load transfer by aggregate
interlock
Reinforcement in rigid pavements

46. e Distributed
fabric
steel reinforcement of wire
■ They are also called bar matts are and are used
without
to control temperature cracking
increasing structural capacity.
■ It is
and
■ The
usually placed at the mid depth of the slab
discontinued at joints.
purpose of distributed steel or temperature
steel is basically one of crack control.
Temperature steel will not prohibit the formation
of cracks but acts as a tie member, which
controls the width of the crack opening.
■ It holds tight ly closed any cracks that may form,
thus maintaining the pavement as integral
structural unit.
Reinforcement in rigid pavements

47. Joints in rigid pavements
J oi nt s are placed in concrete pavements,
whether
expansion
thereby
reinforced or not
of the
to permit
and contraction pavement,
relieving stresses due to
and
environmental changes (temperature
moisture),
construction.
friction, and to facilitate
Contraction joints
■ Provided to relieve the
temperature, moisture
controlling cracking.
tensile stresses due to
and friction, therefore

48. E xpansion joints
Reinforcement in rigid pavements
■ They are transverse and are used to relieve
compressive st resses
concrete.
fram the expansion of
■ They are expensive to maintain and are
susceptible to pumping.
■ The primary function of an expansion joint is to
the
provide space for the expansion of
pavement, thereby preventing the development
of compressive stresses, which cause the
pavement to buckle.

49. Joints in rigid pavements
e Warping joints
■ Allow a slight relative rotation of the slab portions
delimited by joints and reduce the strains due to
warp
.
ng.
i
■ Warping joints are also
always
contraction joints.
Longitudinal joints are warping joints but
they can be found also as transverse joints in some
cases.
Construction joints
■ Are required to facilitate construction, especially
when concreting is stopped.
■ For JUCP and JRCP
, they shall be coupled with
other joints and additional reinforcement shall be
placed when dealing with transverse construction
joints for CRCP

50. @ These result from:
■ Traffic loading
■ Temperature differentials
■ Moisture
■ S
ubgrade movement (volumet ric changes)

51. The principal structural requirements for pavements
The subgrade should be able to sustain traffic loading without excessive
deformation; this is controlled by the vertical compressive stress or strain at this
level.
Bituminous materials and cement-bound materials used in road-base design should
not crack under the influence of traffic; this is controlled by the horizontal tensile
stress or strain at the bottom of the bound layer.
The road-base is often the main structural layer of the pavement, required to
distribute the applied traffic loading so that the underlying materials are not
overstressed. It must be able to sustain the stress and strain generated within itself
without excessive or rapid deterioration of any kind. To control fatigue cracking
caused by load repetitions.
In pavements containing bituminous materials, the internal deformation of these
materials must be limited.
The load spreading ability of granular sub-base and formation layers must be
adequate to provide a satisfactory construction platform.

52. Factors affecting pavement design
• Traffic and loading
• Environment factors
• Materials characteristics
• Design Method.
• Economic considerations

53. Highway Geometric
Design

54. 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 :
1. Cross section elements
2. Sight distance considerations
3. Horizontal alignment details
4. Vertical alignment details
5. Intersection elements

55. Design Controls and criteria
The geometric design of highways depends on several design
factors. The important of these factors which control the
geometric elements are:
• Design speed
• Topography
• Traffic factors
• Design hourly volume and capacity
• Environmental and other factors
Design speed
• In Uganda different speed standards have been assigned
for different class of road.
• Design speed may be modified depending upon the
terrain conditions.

56. opography
• Classified based on the general slope of the country.
• Plane terrain <10%
• Rolling terrain 10-25%
• Mountainous terrain 25-60%
• Steep terrain >60%
Traffic factor
• Vehicular characteristics and human characteristics ofroad users.
• Different vehicle classes have different speed and
acceleration characteristics, different dimensions and
weight .
• Human factor includes the physical, mental and
psychological characteristics of driver and pedestrian.

57. Design hourly volume and capacity
• Traffic flow fluctuating with time
• Low value during off-peak hours to the highest
value during the peak hour.
• It is uneconomical to design the roadway for peak
traffic flow.
Environmental factors
• Aesthetics
• Landscaping
• Air pollution
• Noise pollution

58. 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:
▪ Friction
▪ Pavement unevenness
▪ Light reflecting characteristics
▪ Drainage of surface water

59. Friction
• Skidding: when the path travelled along the road surface is
more than the circumferential movement of the wheels
due to their rotation.
• 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

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

61. 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.
• 250 cm/km for a speed of 100kmph and more than 350
cm/km considered very unsatisfactory even at speed of 50
kmph.

62. 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

63. Bump Integrator

64. Light reflecting characteristics
• Night visibility very much depends upon the light
reflecting characteristics of the pavement surface
• The glare caused by the reflection of head light is
high on wet pavement surface than on dry
pavement particularly in case of black top pavement
or flexible pavement.
• Light colored or white pavement or rigid pavement
surface give good visibility at night particularly
during the rain, and produces glare or eye strain
during bright sunlight.

65. Highway cross section elements
• Carriageway
• Shoulder
• Roadway width
• Right of way
• Building line
• Control line
• Median
• Camber/ cross slope
• Crown
• Side slope
• Kerb
• Guard rail
• Side drain
• Other facilities
The principal elements of a highway cross section consist of the
travel lanes, shoulders, and medians (for some multilane
highways). Marginal elements include median and roadside
barriers, curbs, gutters, guard rails, sidewalks, and side slopes.
Figure 1 shows a typical cross section for a two-lane highway, and
Figure 2 on the next page shows that for a multilane highway.

66. Figure 1 Typical Cross Section for Two-Lane Highways

67. Figure 2 Typical Cross Section for Multilane Highways (half section)

68. Carriageway
:
• 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.
• As per IRC specification, the maximum width of
vehicle is 2.44m,minimum clearance of 0.68 in
case of single lane and 1.02m in case of double
lane.

69. 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
WIDTH OF ROADWAY OF VARIOUS CLASSES OF ROADS
SL. No. Road classification Roadwaywisth
Plane and rolling terrain Mountainous and steep
terrain
1 NH & SH
a) Single lane
b) two lane
12
12
6.25
6.25
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

70. Two lane two-way road
carriageway

71. Shoulder:
• It is provided along the road edge to serve as an
emergency lane for vehicle.
• It act as a service lane for vehicles that have broken
down.
• 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 should 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.

72. shoulder
Footpath
Cycle track

73. unTreated
shoulder
Treated
shoulder

74. 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.
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.

75. Building lane:
• 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.
Control lines:
• In addition to “building line”, it is desirable to control the
nature of building upto further “set back distance” .

76. 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.

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

78. 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.
• To prevent the entry of water into the bituminous
pavement layer.
• To remove the rain water from the pavement
surface as quick as possible and to allow the
pavement to get dry soon after the rain.
• It is expressed as a percentage .
• It depends on the pavement surface and amount of
rainfall.

79. Shape of the cross slope:
• Parabolic shape(fast moving vehicle)
• Straight line
• Combination of parabolic and straight line
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 light
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 1 in 25(4%) 1 in 33(3%)

80. EXAMPLE-1
In a district where the rainfall is heavy, major
district road of WBM pavement, 3.8 m wide,
and a state highway of bituminous concrete
pavement, 7.0 m wide are to be constructed.
What should be the height of the crown with
respect to the edges in these two cases ?

81. Solution
For WBM road
Provide a camber rate of 1 in 33 as the rainfall is
heavy. Rise of crown with respect to edges
For bituminous concrete road
Provide a cross fall of 1 in 50 Rise of crown with
respect to the edges

82. Too steep slope is not desirable because of the fallowing
reasons
• Uncomfortable side thrust and unequal wear of the tyres as
well as road surface.
• Problem of toppling over highly laden bullock cart and truck.
• Tendency of most of vehicle travel along the centre line.
Kerb:
• It indicates the boundary between the pavement and 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.

83. 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 parking the 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.

84. kerb

85. Guard rail
• It is provided at the edge of the shoulder
when the road is constructed on a fill exceeds
3 m.
• 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.

86. Guard rail

87. Road
margins
Parking lane:
• These are provided on urban roads to allow kerb parking
• As far as possible only parallel parking should be allowed
as it is safer for moving vehicle.
•It should have sufficient width say 3m
Lay bay:
• These are 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.
Bus bays:
• These may be provided by recessing the kerb to avoid
conflict with moving traffic.
• It is located atleast 75m away from the intersection.

88. Frontage road:
• These are provided to give access to properties along an important
highway with control access to express way or free way
• It may run parallel to the highway and are isolated by separator.
Driveway:
• It connect the highway with commercial establishment like fuel stations,
service stations etc…
• It should be located away from the intersection.
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.
Footpath:
• These are provided in urban areas when the vehicular as well as
pedestrian traffic are heavy.
• Toprotect the pedestrian and decrease accident.
• Minimum width of 1.5m is provided.

90. Bus
bays

91. Frontage
road

92. c/s of highway in hilly area

93. c/s of road in built-up area

94. C/S of Flexible pavement
C/S of Rigid pavement

96. c/s of road in cutting

97. Guard rails

98. Highway alignment and
surveys

99. Highway alignment
• The position or lay out of centre line of the highway
on the ground is called the alignment.
• It includes straight path, horizontal deviation and
curves.
• Due to improper alignment , the disadvantages are,
➢Increase in construction
➢Increase in maintenance cost
➢Increase in vehicle operation cost
➢Increase in accident cost
• Once the road is aligned and constructed, it is not
easy to change the alignment due to increase in
cost of adjoining land and construction of costly
structure.

102. ➢ Short
➢ Easy
➢ Safe
➢ Economical
• Short- desirable to have a short alignment between two
terminal stations.
• Easy- easy to construct and maintain the road with minimum
problem also easy for operation of vehicle.
• Safe- safe enough for construction and maintenance from
the view point of stability of natural hill slope, embankment
and cut slope also safe for traffic operation.
• Economical- total cost including initial cost, maintenance
cost and vehicle operation cost should be minimum.
Requrements of highway alignment

103. Factors controlling alignment
➢ Obligatory points
➢ Traffic
➢ Geometric design
➢ Economics
➢Other considerations
Additional care in hill roads
➢ Stability
➢ Drainage
➢ Geometric standards of hill roads
➢ Resisting length

104. Factors controlling alignment cont...
Obligatory points
▪ 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…
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.

105. 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
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

106. Topographical control points
• The alignment, where possible should avoid
passing through
▪ Marshy and low lying land with poor drainage
▪ Flood prone areas
▪ Unstable hilly features
Materials and constructional features
▪ Deep cutting should be avoided
▪ Earth work is to be balanced; quantities for filling
and excavation
▪ Alignment should preferably be through better soil
area to minimize pavement thickness
▪ Location may be near sources of embankment
and pavement materials

107. 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.

108. Before a highway alignment is finalised in
highway project, the engineering survey are to be
carried out. The various stages of engineering
surveys are
➢ Map study (Provisional alignment
Identification)
➢ Reconnaissance survey
➢ Preliminary survey
➢ Final location and detailed surveys
Engineering Surveys for Highway locations

109. MAP STUDY
• From the map alternative routes can be suggested
in the office, if the topographic map of that area is
available.
• The probable alignment can be located on the map
from the fallowing details available on the map.
➢Avoiding valleys, ponds or lake
➢Avoiding bend of river
➢If road has to cross a row of hills, possibility of
crossing through mountain pass.
• Map study gives a guidance of the routes to be
further surveyed in the field

110. RECONNAISSANCE SURVEY
• To confirm features indicated on map.
• To examine the general character of the area in field
for deciding the most feasible routes for detailed
studies.
• A survey party may inspect along the proposed
alternative routes of the map in the field with very
simple instrument like abney level, tangent clinometer,
barometer etc…. To collect additional details.
• Details to be collected from alternative routes during
this
survey are,
➢Valleys, ponds, lakes, marshy land, hill,
permanent structure and other obstruction.
➢Value of gradient, length of gradient and radius of
curve.

111. RECONNAISSANCE SURVEY cont..
➢ Number and type of cross drainage structures.
➢High Flood Level (HFL)
➢Soil Characteristics.
➢Geological features.
➢source of construction materials- stone quarries,
water sources.
• Prepare a report on merits and demerits of different
alternative routs.
• As a result a few alternate alignments may be chosen
for further study based on practical considerations
observed at the site.

112. Preliminary survey
Objective of preliminary survey are:
• To survey the various alternative alignments proposed
after the reconnaissance and to collect all the
necessary physical information and detail of
topography, drainage and soil.
• To compare the different proposals in view
of the requirements of the good alignment.
• To estimate quantity of earthwork materials and other
construction aspect and to workout the cost of the
alternate proposals.
Methods of preliminary survey:
a) Conventional approach-survey party carries out
surveys using the required field equipment, taking
measurement, collecting topographical and other

113. Preliminary survey cont…
• Longitudinal and cross sectional profile.
: 100 – 200m
: 50m
: 30m
➢ Plain Terrain`
➢ Rolling Terrain
➢ Hilly Terrain
• Other studies
➢ Drainage, Hydrological survey, soil survey, Traffic and
Material survey.
b) Modern rapid approach-
By Aerial survey taking the required aerial photographs for
obtaining the necessary topographic and other maps
including details of soil and geology.
• Finalise the best alignment from all considerations by
comparative analysis of alternative routes.

114. Final location and detailed survey
• The alignment finalised at the design office after the
preliminary survey is to be first located on the field by
establishing the centre line.
Location survey:
• Transferring the alignment on to ground.
• This is done by transit theodolite.
• Major and minor control points are established on the
ground and centre pegs are driven, checking the
geometric design requirements.
• Centre line stacks are driven at suitable intervals, say 50m
interval in plane and rolling terrains and 20m in hilly
terrain.

115. Final location and detailed survey cont..
Detailed survey:
• Temporary bench marks are fixed at intervals of about
250m and at all drainage and under pass structure.
• Earthwork calculations and drainage details are to be
workout from the level books.
• Cross sectional levels are taken at intervals of 50-100m
in Plane terrain, 50-75m in Rolling terrain, 50m in built-
up area, 20m in Hill terrain.
• Detail soil survey is to be carried out.
• CBR value of the soils along the alignment may be
determined for design of pavement.
• The data during detailed survey should be elaborate and
complete for preparing detailed plans, design and
estimates of project.

116. Drawing and Report
▪ Key map
▪ Index map
▪ Preliminary survey plans
▪ Detailed plan and longitudinal section
▪ Detailed cross section
▪ Land acquisition plans
▪ Drawings of cross drainage and other retaining
structures
▪ Drawings of road intersections
▪ Land plans showing quarries etc

117. New highway project
• Map study
• Reconnaissance survey
• Preliminary survey
• Location of final alignment
• Detailed survey
• Material survey
• Geometric and structural design
• Earth work
• Pavement construction
• Construction controls

118. Bibliography
• Khanna, S. K., & Justo, C. E. G. Highway
engineering. Nem Chand & Bros.
• IRC Codes.
• Khanna, S. K., & Justo, C. E. G. “Highway
engineering”. Nem Chand & Bros.
• IRC Codes.