Major disciplines of transportation

Transportation engineering can be broadly consisting of the the four major

parts:

 Transportation Planning
 Geometric Design
 Pavement Design
 Traffic Engineering

NATIONAL HIGHWAY

They are main highways running through the length and breadth of India
connecting major ports , Foreign highways, capitals of large states and
large industrial and tourist centers including roads required For strategic
movements.

• It was recommended by Jayakar committee that the National highways

should be the frame on which the Entire road communication should be
based.

They are constructed and maintained by CPWD.

The total length of National highway in the country is 58,112 Kms, and
constitute about 2% of total road networks of India and carry 40% of total
traffic.

STATE HIGHWAY

• 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

• They also serve as main arteries to and from district roads.

They are maintaining by STATE GOVERNMENT

• Total length of all SH in the country is 1,37,119 Kms.

MAJOR DISTRICT ROAD

• 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.

OTHER DISTRICTS ROAD

• Roads serving rural areas of production and providing them with outlet
to market centers or other important roads like MDR or SH.

It is used in mostly local connectivity.

VILLAGE ROAD

• They are roads connecting villages or group of villages with each other
or to the nearest road of a

FREEWAYS:- Freeways are access controlled divided highways. Most

freeways are four lanes, two lanes Each direction, but many freeways
widen to incorporate more lanes as they enter urban areas. Access Is
controlled through the use of interchanges, and the type of interchange
depends upon the kind of Intersecting road way (rural roads, another
freeway etc.)

EXPRESSWAYS : They are superior type of highways and are designed

for high speeds ( 120 km/hr is common), High traffic volume and safety.
They are generally provided with grade separations at intersections.
Parking, loading and unloading of goods and pedestrian traffic is not
allowed on expressways.

HIGHWAY ALIGNMENT

The position or the layout of the central line of the highway on the ground
is called the alignment. horizontal alignment includes straight and curved
paths. vertical alignment includes level and gradients. alignment decision
is important because a bad alignment will enhance the construction,
maintenance and vehicle operating cost. once an alignment is fixed and
constructed, it is not easy to change it due to increase in cost of adjoining
land and construction of costly structures by the roadside.

INTRODUCTION TO GEOMETRIC DESIGN

The geometric design of highways deals with the dimensions and layout of
visible features of the highway. The emphasis of the geometric design is to
address the requirement of the driver and the vehicle such as Safety,
comfort, efficiency, etc. The features normally considered are the cross
section elements, sight distance Consideration, horizontal curvature,
gradients, and intersection. The design of these features is to a great
Extend influenced by driver behavior and psychology, vehicle
characteristics, traffic characteristics such as speed And volume.

FACTORS AFFECTING GEOMETRIC DESIGN

1. Design speed
2. Topography
3. Other factored
 Vehicle
 Human
 Traffic
 Environment

INTRODUCTION TO PAVEMENT DESIGN

Requirements of a pavement

 Sufficient thickness to distribute the wheel load stresses to a safe

value on the sub-grade soil
 Structurally strong to withstand all types of stresses imposed upon it
 Adequate coefficient of friction to prevent skidding of vehicles
 Smooth surface to provide comfort to road users even at high speed
 Produce least noise from moving vehicles
 Dust proof surface so that traffic safety is not impaired by reducing
visibility.
 Impervious surface, so that sub-grade soil is well protected
 Long design life with low maintenance cost

 Types of pavements
Rigid pavements

Rigid pavements have sufficient flexural strength to transmit the wheel

load stresses to a wider area below. A typical cross section of the rigid
pavement is shown in Figure 19:3. Compared to flexible pavement, rigid
Pavements are placed either directly on the prepared sub-grade or on a
single layer of granular or stabilized Material. Since there is only one layer
of material between the concrete and the sub-grade, this layer can be
Called as base or sub-base course.

3 number of layer and thickness is less as compared to flexible

pavement

Types of Rigid Pavements

1. Jointed plain concrete pavement (JPCP)
JPCP is the most commonly used type of rigid pavement. It consists
of long slabs of concrete with transverse and longitudinal joints.
Transverse joints are typically spaced at regular intervals to control
cracking caused by the natural expansion and contraction of the
concrete due to temperature changes. Longitudinal joints are placed
at the edges of the pavement and provide lateral support to the
slabs. JPCP is cost-effective and relatively easy to construct.
2. Jointed reinforced concrete pavement (JRCP)
JRCP is similar to JPCP but includes steel reinforcement within the
concrete slabs. The reinforcement helps to control cracking and
improve the overall strength of the pavement. It is often used in
areas where heavy truck traffic or high wheel loads are anticipated.
3. Continuous reinforced concrete pavement (CRCP)
CRCP is a type of rigid pavement that does not contain any
transverse joints. Instead, it has continuous steel reinforcement
throughout the entire pavement section. The absence of transverse
joints eliminates the need for joint maintenance and reduces the
potential for faulting and pumping. CRCP is commonly used for
highways and roads with heavy traffic loads.
4. Pre-stressed concrete pavement (PCP).

DESIGN OF JOINTS

Expansion joints The purpose of the expansion joint is to allow the

expansion of the pavement due to rise in temperature with Respect to
construction temperature. The design consideration are:

 Provided along the longitudinal direction,

 design involves finding the joint spacing for a given expansion joint
thickness (say 2.5 cm specified by IRC) subjected to some maximum
spacing (say 140 as per IRC)

Contraction joints The purpose of the contraction joint is to allow the

contraction of the slab due to fall in slab temperature below The
construction temperature. The design considerations are
Dowel bars The purpose of the dowel bar is to effectively transfer the
load between two concrete slabs and to keep the two Slabs in same
height. The dowel bars are provided in the direction of the traffic
(longitudinal).

Their primary function is to provide a mechanical connection between

slabs without restricting horizontal movement.

 Mild steel rounded bars

 bonded on one side and free on other side

Tie bars in contrast to dowel bars, tie bars are not load transfer devices,
but serve as a means to tie two slabs. hence tie bars must be deformed or
hooked and must be firmly anchored into the concrete to function
properly. they are smaller than dowel bars and placed at large intervals.
they are provided across longitudinal joints.

FLEXIBLE PAVEMENTS

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 19:1). The wheel load acting on the pavement will be
Distributed to a wider area, and the stress decreases with the depth.

Taking advantage of this 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.

Flexible pavements are constructed using bituminous materials. These

can be either in the form of surface treatments(such as bituminous
surface treatments generally found on low volume roads) or, asphalt
concrete surface courses (generally used on high volume roads such as
national highways).

The major flexible pavement failures are fatigue cracking, rutting, and
thermal cracking. the fatigue cracking of flexible pavement is due to
horizontal tensile strain at the bottom of the asphaltic concrete. the failure
criterion relates allowable number of load repetitions to tensile strain and
this relation can be determined in the laboratory fatigue test on asphaltic
concrete specimens

Types of Flexible Pavements

Conventional layered 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.

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.

 PAVEMENT MATERIALS: AGGREGATES

Shape of aggregates which happen to fall in a particular size range may

have rounded, cubical, angular, flaky or elongated particles. it is evident
that the flaky and elongated particles will have less strength and
durability when compared with cubical, angular or rounded
particles of the same aggregate. hence too flaky and too much
elongated aggregates should be avoided as far as possible.

Desirable properties

1) Strength
2) Hardness
3) Toughness
4) Shape and size
5) Durability

Aggregate tests

1) Crushing test
2) Abrasion test
3) Impact test
4) Soundness test
5) Shape test
6) Specific gravity and water absorption test
7) Bitumen adhesion test

Bituminous materials or asphalts are extensively used for roadway

construction, primarily because of their excellent binding characteristics
and water proofing properties and relatively low cost. bituminous
materials consists of bitumen which is a black or dark coloured solid or
viscous cementations’ substances consists chiefly high molecular weight
hydrocarbons derived from distillation of petroleum or natural asphalt, has
adhesive properties, and is soluble in carbon disulphide.

Bitumen is the residue or by-product when the crude petrolium is refined.

a wide variety of refinery processes, such as the straight distillation
process, solvent extraction process etc. may be used to produce bitumen
of different consistency and other desirable properties. depending on the
sources and characteristics of the crude oils and on the properties of
bitumen required, more than one processing method may be employed.

Soil Types The wide range of soil types available as highway construction
materials have made it obligatory on the part of the highway engineer to
identify and classify different soils. a survey of locally available materials
and soil types conducted in india revealed wide variety of soil types,
gravel, moorum and naturally occurring soft aggregates, which can be
used in road construction. broadly, the soil types can be categorised as
laterite soil, moorum / red soil, desert sands, alluvial soil, clay including
black cotton soil.

Gravel: These are coarse materials with particle size under 2.36 mm with
little or no fines contributing to cohesion of materials.

TRAFFIC AND LOADING

Equivalent Single Wheel Load (ESWL)

Equivalent Single Axle Load

WBM (WATER BOUND MACADAM):

Water Bound Macadam (WBM) is a type of road construction

material that consists of crushed stone or aggregate bound
together with water and finer material, such as screenings or
stone dust.

 Construction: Aggregates (stone or crushed stone) are laid, then

screened material (finely crushed stone) is added, followed by water
which acts as the binder. These materials are then compacted into a
single layer or multiple layers.
 Materials: Primarily uses crushed stone aggregates and water as
the binder.
 Durability: Generally considered less durable than WMM, as the
binding relies on water evaporation and compaction.
 Cost: Can be less expensive than WMM, especially in areas with
readily available crushed stone and water.
 Open to Traffic: May take longer to dry and open to traffic
compared to WMM.

DRY ROLLING, APPLICATION OF SCREENING, WET ROLLING, AND

APPLICATION OF FILLER

The Water Bound Macadam (WBM) construction process involves several

steps:

Step 1: Preparation of Base

 *Clearing and grubbing*: Clear the area of vegetation, debris, and

other obstacles.
  *Grading*: Grade the base to the required level and camber.

Step 2: Spreading of Aggregate

 *Spreading*: Spread the aggregate material evenly over the

prepared base.
 *Thickness*: Ensure the aggregate layer is of the required thickness.

Step 3: Rolling

 *Rolling*: Compact the aggregate layer using a roller to achieve the

desired density.
 *Multiple passes*: Make multiple passes with the roller to ensure
adequate compaction.

Step 4: Application of Screenings

 *Spreading screenings*: Spread screenings or stone dust over the

compacted aggregate layer.
 *Brooming*: Use brooms to spread the screenings evenly and fill the
voids.

Step 5: Watering and Rolling

 *Watering*: Apply water to the surface to help the screenings

penetrate the aggregate layer.
 *Rolling*: Continue rolling to compact the layer and achieve the
desired density.

Step 6: Final Compaction

 *Final rolling*: Perform final rolling to achieve the desired surface

finish and density.
 *Inspection*: Inspect the surface for any defects or irregularities.

Step 7: Maintenance

 *Regular maintenance*: Regularly inspect and maintain the WBM

surface to prevent deterioration.
 *Repair*: Repair any defects or damage promptly to ensure the
longevity of the WBM surface.

WMM (WATER MIX MACADAM):

1. *Mixing*: Mix aggregates, binder (e.g., bitumen emulsion or cement),

and water in a controlled environment.
2. *Laying*: Lay the WMM mix on a prepared surface using a paver or
grader.
3. *Compaction*: Compact the WMM layer using rollers to achieve the
desired density.
4. *Curing*: Allow the WMM layer to cure, either naturally or with the
application of water or other treatments.
Applications:
1. *Road construction*: WMM is used as a base course or binder course in
road construction.
2. *Highway construction*: WMM provides a strong and durable base for
highways.
Benefits:
1. *Improved strength*: WMM offers better strength and stability
compared to traditional macadam.
2. *Better durability*: WMM is more resistant to water and traffic loads.

3. *Reduced maintenance*: WMM requires less maintenance compared to

other materials.

 Light reflection
 White roads have good visibility at night, but caused glare during
day time.
 Black roads has no glare during day, but has poor visibility at night
 Concrete roads has better visibility and less glare

 Camber

Camber or cant is the cross slope provided to raise middle of the road
surface in the transverse direction to Drain off rain water from road
surface. The objectives of providing camber are:

 Surface protection especially for gravel and bituminous roads

 Sub-grade protection by proper drainage
 Quick drying of pavement which in turn increases safety

Width of carriage way

Width of the carriage way or the width of the pavement depends on the
width of the traffic lane and number of lanes. width of a traffic lane
depends on the width of the vehicle and the clearance. side clearance
improves operating speed and safety. the maximum permissible width of a
vehicle is 2.44 and the desirable side clearance for single lane traffic is
0.68 m. this require minimum of lane width of 3.75 m for a single lane
road (figure 12:2a). however, the side clearance required is about 0.53 m,
on either side and 1.06 m in the center. therefore, a two lane road require
minimum of 3.5 meter for each lane (figure 12:2b). the desirable carriage
way width recommended by irc is given in table 12:2

CERBS:-
A road kerb, also known as a curb in American English, is a raised
edge or barrier typically found along the edge of a road or
sidewalk. Its primary purpose is to prevent vehicles from veering
off the road and into adjacent areas like sidewalks or footpaths,
enhancing road safety. Kerbs also help define the boundary
between the road and other areas, contributing to visual clarity
and organization.
ROAD MARGINS

The portion of the road beyond the carriageway and on the roadway can
be generally called road margin. Various elements that form the road
margins are given below.

1) SHOULDERS

Shoulders are provided along the road edge and is intended for
accommodation of stopped vehicles, serve as an emergency lane for
vehicles and provide lateral support for base and surface courses. The
shoulder should be strong enough to bear the weight of a fully loaded
truck even in wet conditions. The shoulder width should be adequate for
giving working space around a stopped vehicle. It is desirable to have a
width of 4.6 m for the shoulders. A minimum width of 2.5 m is
recommended for 2-lane rural highways in India.

2) PARKING LANES

Parking lanes are provided in urban lanes for side parking. parallel parking
is preferred because it is safe for the vehicles moving in the road. the
parking lane should have a minimum of 3.0 m width in the case of parallel
parking.

3) BUS-BAYS

Bus bays are provided by recessing the kerbs for bus stops. They are
provided so that they do not obstruct the movement of vehicles in the
carriage way. They should be at least 75 meters away from the
intersection so that the traffic near the intersections is not affected by the
bus-bay.

4) FOOTPATH
5) CYCLE TRACK

6) RIGHT OF WAY:-
SIGHT DISTANCE

Sight distance refers to the length of roadway a driver can see ahead, and
it’s crucial for safe driving and road design. There are three main types of
sight distance: stopping sight distance, passing sight distance, and
intersection sight distance

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.

1. Stopping Sight Distance (SSD): This is the minimum distance a

driver needs to see an object on the road and safely come to a stop before
hitting it. It’s essential for preventing collisions with stationary objects or
other vehicles. Lag distance is the distance the vehicle traveled during the
reaction time t and is given by vt, where v is the velocity in m/sec2

2. Passing Sight Distance (PSD): This is the distance a driver needs to

see along the road to safely overtake another vehicle. It’s crucial for two-
lane roads where passing maneuvers are common.

3. Intersection Sight Distance (ISD): This is the distance a

driver needs to see to safely enter or cross an intersection. It's
important for drivers to make informed decisions about crossing
or merging traffic.
4. Headlight Sight Distance (HSSD): This refers to the distance visible
to drivers at night under the illumination of headlights.

TYPES OF TRAFFIC SIGNS

 MANDATORY/REGULATORY /PROHIBITORY SIGNS

Mandatory Signs: These signs, also known as regulatory signs, require

drivers to obey them, often specifying actions that must be taken or
prohibited. They are typically circular with a white background and a red
border. Common examples include speed limit signs, “No Entry”, “Give
Way”, and “Horn Prohibited” signs.

COLOUR:- RED BORDER, WHILE BACKGROUND, BLACK SYMBOL

 INFORMATORY SIGNS:

Informatory Signs: These signs provide general information to drivers

about the road and its features, such as distances to destinations, services
along the way, or important landmarks. They can be rectangular or square
and use text and symbols to convey the information. Examples include
directional signs, place identification signs, and service station indicators.

1. Shape Rectangular and square

2. Colour:- Blue

 WARNING SIGNS/ CAUTIONARY SIGNS

Warning signs or cautionary signs give information to the driver about the
impending road condition. They Advice the driver to obey the rules. These
signs are meant for the own safety of drivers. They call for extra Vigilance
from the part of drivers.

1. Shape :- Triangular in shape

2. Colour :- COLOUR:- RED BORDER, WHILE BACKGROUND,
BLACK SYMBOL
ROAD MARKINGS

The road markings are defined as lines, patterns, words or other devices,
except signs, set into applied or attached to the carriageway or kerbs or to
objects within or adjacent to the carriageway, for controlling, warning,
guiding and informing the users. the road markings are classified as
longitudinal markings, transverse markings, object markings, word
messages, marking for parkings, marking at hazardous locations etc.

 Longitudinal markings:- they are marked along the direction of

traffic on the roadway surface, for the purpose of indicating to the
driver, his proper position on the roadway. some of the guiding
principles in longitudinal markings may also be discussed.
1. Yellow line :- Restriction Line
2. White line:- Guide line
  Transverse Markings:
 Stop Lines: Thick white lines painted across the road at
intersections, indicating where vehicles should stop.
 Crosswalks: Markings for pedestrians to cross the road safely.
 Give Way Lines: Lines indicating where vehicles must yield the
right of way.
 Chevron Markings: Lines used to warn of road width reductions or
potential hazards.

Block markings on roads are transverse markings, often

appearing as blocks, used to indicate specific actions or locations
for traffic control, such as zebra crossings, speed bump markings,
or “Give Way” symbols.

Hazard markings on roads are visual cues, like chevron and

diagonal stripes, used to alert drivers about potential dangers
and guide them through complex traffic situations. These
markings, often yellow or white, help manage merging, diverging,
and redirection of traffic, ensuring smoother and safer road
travel.
 TRAFFIC INTERSECTIONS
At grade intersection control
1. Diamond interchange
2. Rotary/Round about

Channalized intersection

1. Trumpet interchange
2. Cloverleaf interchange