te_5th sem 2007
TRANSCRIPT
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TRANSPORTATION ENGINEERING
TRAFFIC
ENGINEERING
PUBLIC
TRANSPORTATION
TRANSPORT
PLANNING
TRANSPORT
ECONOMICS
PAVEMENT
ENGINEERING
FUNCTIONAL CLASSIFICATION
ROADWAYS RAILWAYS WATERWAYS AIRWAYS
MODAL CLASSIFICATION
PUBLIC
CAR
ROADS
SIGNALS
PARKING LOTS
PUBLIC
TRAIN DRIVER
LOCO & COACHES
RAIL TRACKS
SIGNALS
STATIONS
PASSENGERS
CAPTAIN
SHIP
SHIPPING LINES
COAST GUARD
PORTS
PASSENGERS
PILOTS
AIRCRAFT
AIR ROUTS
AIR TRAFFIC CONTROL
AIR PORT
PASSENGERS
DRIVER
VEHICLE
WAY
CONTROL
TERMINAL
USER
ELEMENTAL CLASSES
FIGURE: CLASSIFICATION SCHEME USED FOR TRANSPORTATION ENGINEERING
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ROAD DEVELOPMENT IN INDIA
• In 25 – 35 B.C : MAHENJEDARO & HORAPPA• In 4TH Century B.C : ARYAN PERIOD
• In 5TH Century B.C : IMPERIAL GUPTA
• In 16TH – 18TH Century: MUGHAL EMPIRE
– Development of first class system of communication through a welldeveloped road system
– Major Routes were:• Patna – Kabul
• Delhi – Surat
• Delhi – Golconda
• Golconda – Bijapur • Bijapur – Ujjain
• Surat – Masulipatam
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• MODERN PERIOD
Under British Rule till the end of the 19th Century
First major reform in public road construction inaugurated during leadership of Lord
William Bentinck from 1828
A better era was followed during the rule of Lord Dalhousie (1848 – 56); PWD established
Road Development Committee (1927)
Under Mr. M. R. Jayakar, MLA, as chairman
The Road development committee known as Jayakar Committee
Set up November, 1927
Final report was published in November, 1928.
Recommendations
Road development should get National importance
Central Road Fund to be set up to generate revenue by additional
taxation on motor fuel, vehicle taxation, license fees for vehicles on hire A semi-official technical body should be formed
A research organization should be instituted to carry out research and
development work and to be available for consultations.
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Summery
Most of the recommendations of the Jayakar Committee were accepted by the
Govt.
Implementation
C.R.F – 1929
IRC - 1934 (semi official technical body)
CRRI- 1950 (a research organization)
Motor Vehicles Act – 1939 (revised in 1988)
Nagpur Road CongressChief Engineers of all States and Provinces were called by the Govt. of India tomeet at Nagpur in December, 1943 to discuss planning of post war road
development.
Known as 1st 20 years Road Development Plan in India (1943 – 1963)
Recommendations of Nagpur Road Plan
Road was classified in to four classes
1. National Highways: Traverse several provinces or states,
National Importance for Strategic, administrative and other
purpose
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2. State Highways: would be other main roads of states
3. District Roads: would take traffic from the main roads to the
interior of each district or similar unit- MDR, ODR
4. Village Road: which essentially farm tracks, to be designed,constructed and maintained under the authority of the State
Highways Department
Construction of NH – Central Govt.
Plan Period 20 years (1943-1963), target road length 16 km per 100 sq.
km. of agricultural area, planed decision were taken based on
agricultural and non-agricultural area.
Star and Grid pattern of road network considered
grid length for agricultural area – 16 km
grid length for non-agricultural area – 64 km
Bombay Road Plan ( 1961-1981) : 2nd 20 year road plan
Lucknow Road plan (1981- 2001) : 3rd 20 year road plan
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Present Road Development work in India
Function of National Highways Authority of India (NHAI) The National Highways Authority of India was constituted by an act of
Parliament, the National Highways Authority of India Act, 1988, It is responsible for the development, maintenance and management of National
Highways in India.
The NHAI is mandated to implement National Highways DevelopmentProject (NHDP)
India's Largest ever highways project- World class roads with uninterrupted traffic flow- Major initiative for capacity enhancement of National Highways- Four/Six Laning of around 13,146 Km- Total Cost Rs. 54,000 crores
In addition to implementation of National Highways Development Projects, the NHAIis also responsible for implementing some projects on National Highways other thanNHDP.NHAI is now responsible for implementing on National Highways of length
around 10,000 Km.
Up gradation of Rural Road Pradhan Mantri Gram Sadak Yojona
Based on Habitation of the Village
Core-network to be developed to connect the village through all weather road
Monitoring agency set up – State Technical Agency
Formulation and Planning – National Rural Road Development Agency Setup
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Indian ROAD NETWORKS
Indian road network of 33.4 lakh Km.is secondlargest in the world and consists of :
Types of Road network Length (in Km.)
EXPRESSWAYS 200
NATIONAL HIGHWAYS 66,590
STATE HIGHWAYS 1,28,000
MAJOR DISTRICT ROADS 4,70,000
RURAL AND OTHER ROADS 26,50,000
TOTAL LENGTH 33.4 LAKHS (APPROX.)
Status of National Highways as on
30
th
November, 2006
SingleLane/Intermed
iate lane
35%
Double Lane 55%
Four or morelanes
10%
About 65% of freight and 80% passenger traffic is carried by theroads
National Highways constitute only about 2% of the road networkbut carry about 40% of the total road traffic.
The growth of vehicles observed at an average pace of 10.16%per annum over the last five years.
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Figure: National Highways Development Projects in India
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“Transportation Engineering”
Transportation Engineering is the application of scientific process (like observation,
analysis and deduction) to the planning, design, operation and management of
transportation facilities.
Transportation Engineering is also multidisciplinary and require knowledge from
specialized fields such as psychology, economics, ecology and environment, sociology,
management, optimization, graph theory, probability theory, statistics, computer
simulation and other area of civil engineering (such as structural and geothecnical ).
Role of Transportation Engineering
The Institute of Transportation Engineers (1987) defines transportation engineering
as”the application of technological and scientific principles to the planning, functionaldesign, operation and management of facilities for any mode of transportation in order to
provide for the safe, rapid,comfortable, convenient, economical and environmentally
compatible movement of people and goods”.
Traffic Engineering, a branch of transportation engineering, is described as “thatphase of transportation engineering which deals with planning, geometric design, and
traffic operations of roads, streets and highways, their networks, terminals, abutting
lands and relationship with other modes of transportation”.
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Necessity of Highway Planning
Highway planning is a basic need for highway development. Particularly planning
is of great importance when the funds available are limited whereas the total requirement is
much higher.
Objective
To plan a road network for efficient and safe traffic operation, but at minimum cost.
To arrive at the road system and lengths of different categories of roads which could be
constructed within the available resources during the plan period under consideration.
To fix up date wise priorities for development of each road link based on utility as the
main criterion for phasing the road development program.
To plan for future requirements and improvements of roads in view of anticipated
development.
To work out financing system.
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Planning Surveys
Highway planning phases are:
Assessment of road length requirement for an area ( it may be a district, state
or the whole country)
Preparation of master plan showing phasing of plan in annual and or five year
plans
For assessing the road length requirement, field surveys are to be carried out to
collect the data required for determining the length of the road system.
The field (data) surveys thus required for collecting the factual data may be called as
planning surveys or fact finding surveys.
The planning surveys consists of the following studies:
A. Economic Studies
B. Financial Studies
C. Traffic or road user Studies
D. Engineering Studies
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A. Economic Studies
Population and its distribution in village, town or district or other locality with the
area classified groups
Population growth trend
Agricultural and Industrial products and their listing in classified groups, area wise
Future trend of agricultural and industrial development
Existing facilities with respect to communication, recreation and education etc.
Per capita income
B. Financial Studies
Essential to study the varies financial aspects like sources of income and the
manner in which funds for the project may be mobilized.
The Details are
Sources of income and revenue from taxation on road project
Living standard
Resources at local level, toll taxes, vehicle registration and fines – BOT
Future trends in financial aspects
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C. Traffic and Road Use Studies
All existing traffic details such as volume, flow pattern etc. to be collected before any
improvement could be planned.
Traffic survey should be carried out in the whole area and on selected routes andlocations and also by dividing the total route into homogeneous sections in order to
collect the following particulars.
Traffic Volume in Vehicle/day (ADT), annual average daily traffic (AADT), Peak hour
traffic and design hourly traffic volume.
Origin Destination Studies
Traffic Flow Patterns at junctions
Mass transportation facilities
Accidents, their causes, cost analysis
Future growth trend in traffic volume and goods traffic
Growth of passenger trips and the trend in the choice of mode
Axle load survey to find the axle load spectrum
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D. Engineering Studies
The engineering studies includes the followings
Topographic Survey – to create topographic Map for final alignment designSoil survey – soil investigation requires for design of pavement components etc.
Location and classification of existing roads
Road life studies
Traffic studies
Road Condition Survey – to evaluate the present structural condition of the road
Condition of bridge and culvert etc.
Special problems in drainage, construction and maintenance of road
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Classification of Rural Road – (IRC 73: 1980)
National Highway - NH
State Highway - SH
Major District Road - MDR
Other District Road - ODR
Village Road – VR
Classification of Urban Road – (IRC 86: 1983)
Arterial Road
Sub-arterial Road
Collector Street
Local Street
Road Patterns
o Rectangular or block pattern
o Radial or star and block pattern
o Radial or star and circular pattern
o Radial or star and grid pattern
o Hexagonal pattern
o Minimum travel pattern
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Highway Alignment
Layout of the Central Line of the highway on the ground is known as alignment
Horizontal alignment : Include Straight and horizontal curve
Vertical alignment : Gradient and vertical curve
Basic requirement of an ideal alignment
Short – Shortest between two terminals
Easy – Construction and maintenance of the highway must be easy
Safe – Should be safe against construction and maintenance, natural slope
stability, traffic operation with geometric features
Economical – Final cost should be minimum with respect to initial cost.
Methods of alignment survey
New Alignment – GIS method
Existing Alignment – Conventional method
Engineering Survey for Highway Location
Map Studies
Reconnaissance survey
Preliminary survey
Detail survey
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Detail survey
Establishing the Central Line of the proposed route
Establishing Bench Mark at suitable point
Detail survey of topography, soil investigation, leveling work etc.
Preparation of Drawing and Report
Key Map
Index Map
Preliminary Map
Detail plan and longitudinal profile
Detailed Cross-section
Land acquisition plans
Drawings of detail Cross drainage and other retaining structures
Drawings of road intersections
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HIGHWAY GEMETRIC DESIGN
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Highway Geometric Design
• Highway Geometric Design is an aspect of highway design dealing with thevisible dimensions of a roadway
• Proper designing of the layout of a road is important from two aspects:
It facilitates smooth flow of traffic and
It improves safety
These improvements derived from:
I. Good geometric design of direction changes in road
II. Good geometric design of slope changes in roads
III. Good delineation of desirable vehicular paths at confusing locations such as
intersections
Layout design of road sections joining two roads with different directions is
referred to as geometric design of horizontal curves
Layout design of road sections joining two roads with different gradients (or
slope) is referred to as geometric design of vertical curves
Layout design of road section for the purpose of proper delineation of vehicular
paths is referred to as channelization design
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Task of Geometric Design of highway
Cross Sectional Elements
Sight Distances
Horizontal AlignmentVertical Alignment
Intersection
Typical road cross-sectionFormation width
Carriageway
Right-of-way (ROW)
Roadway
G.L
Shoulder
Road Boundary
Building Line
Control Line
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Terrain Classification
Sl. No. Terrain Classification Percent Cross-slope of the country
1 Level/Plain 0 to 10
2 Rolling 10 to 253 Mountainous 25 to 60
4 Steep Greater than 60
The classification of the terrain is done by means of the cross-slope of the country.
Plain & Rolling Terrain Mountainous & Steep Terrain
For NH and SH
Single Lane 12.0 m. 6.25 m.
Two Lane 12.0 m. 8.80 m.
MDR
Single Lane 9.0 m. 4.75 m.
Two Lane 9.0 m. 4.75 m.
Road Way Width as per IRC
The minimum roadway width on single lane bridge is 4.25 m.
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Class of
Road
Plain and Rolling Terrain Mountainous Terrain
Rural Area Urban Area Rural Area Urban area
Normal Range Normal Range Normal Exceptional Normal Exceptional
NH
& SH
45 m (30 – 60) m 30 m (30 – 60) m 24 m 18 m 20 m 18 m
MDR 25 m (25 – 30)m 20 m (15 – 25) m 18 m 15 m 15 m 12 m
ODR 15 m (15 – 25) m 15 m (15 – 20) m 15 m 12 m 12 m 9 m
Right-of-way (ROW) width for different classes of Roads in India
Carriage way width
The width of the pavement is the carriage way width (Ref: IRC : 86-1983)
Class of Road Carriage way width (m)
Single Lane 3.75
Two lanes without raised kerbs 7.0
Two Lanes with raised kerbs 7.5
Intermediate Carriage way 5.5
Multilane Pavements 3.5 per Lane
The maximum width of vehicle as per IRC specification is 2.44 m.
Ref: IRC: 52 - 1981
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Shoulder
The shoulder is that part or portion of the roadway contiguous with traveled
way and is intended for accommodation of stopped vehicles, emergency use and
lateral support of base and surface course.
For Two lane rural roads shoulder width is 2.5 meter.Curbs (Kerbs)
A curb is a vertical or slopping member along
the edge of a pavement or shoulder strengthening or
protecting the edge and clearly defining the edge to
vehicle operators
Camber or cross-slope
Camber, also known as cross-slope facilitates drainage of a pavement laterally.
The amount of camber depends upon the smoothness of the surface and intensity of
rainfall
Fig. Vertical barrier curb
Types of Surface Camber in Percentage (rainfall heavy to light)
1. Cement Concrete or high type bituminous 2 to 1.7
2. Thin bituminous surfacing 2.5 to 2
3. Water bound macadam 3 to 2.5
4. Earth 4 to 3
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Sight Distances
• The clear visible distance available
• The sight distance requirements
# Stopping Sight Distance (SSD)# Overtaking Sight Distance (OSD)
# Intermediate Sight Distance
For operating a motor vehicle safely and efficiently, it is of utmost importance that drivers
have the capability of seeing clearly ahead. Therefore, sight distance of sufficient length
must be provided so that the drivers can operate and control their vehicle safely. Sight
distance – length of roadway ahead visible to the driver – can be discussed in four
important situations
1. The distances required by the motor vehicle to stop
2. The distances needed at complex location
3. The distances required for passing and overtaking vehicles, applicable to twolane highways
4. The criteria for measuring these distances for use in design
IRC recommended that the height of the driver’s eye is 1.2 m and height of the object is
0.15m above the road surface
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Sight Distances
Stopping Sight Distance (SSD)
Stopping sight distance is the distance required by a driver of a vehicle traveling at
given speed to bring his/her vehicle to a stop after an object on the highwaybecomes visible. It is made up of two components
i) the distance traveled during perception and break reaction time; and
ii) the distance travelled during the time the breaks are under application till the
vehicles comes to a stop
Perception time is the time which elapses between the instant the driver perceivesthe object on the carriageway and the instant that the realizes that breaking of the
vehicle is needed
The time lag or the brief interval between the perception of danger and the effective
application of the breaks is called break reaction time
As per IRC a value of 2.5 seconds is considered for perception time and break
reaction time taken together
Stopping Sight Distance = Distance travelled during perception and beak reaction
time + breaking distance (distance in which a moving
vehicle comes to a stop after the application of brakes)
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Stopping Sight Distance (SSD) = 278Vt + V2/(254f)
Where, V = Design Speed km/hr.
t = Perception and break reaction time
= 2.5 second
f = Coefficient of longitudinal friction between the
tyre and the pavement
SSD = in meter
The co-efficient of friction is assumed to vary from 0.40 at 20 kmph to 0.35 at 100 kmph
Effect of longitudinal grade
Stopping Sight Distance (SSD) = 278Vt + V2/254 (f + 0.1G)
G = gradient in percentage
positive sign may used for ascending gradient
negative sign may be taken for descending gradient
For single lane two-way traffic,
SSD = 2 [278Vt + V2/(254f )]Note: Correction for grade should not be applied on undivided roads with two-way traffic
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Speed
(Km/hr)
Safe Stopping Sight
distance (m)
20 20
25 25
30 30
40 45
50 60
60 80
65 90
80 120
100 180
Table: Stopping Sight Distance as per IRC
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Overtaking Sight Distance (OSD)
d1= represents the distance travelled during the perception and reaction time and
during the initial acceleration to the point of encroachment on the right lane
d2 = represents the actual distance covered by the overtaking vehicles during the
overtaking manoeuver
d3 = represents the distance between the overtaking vehicles at the end of its
manoeuver and the opposing vehicle, is known as clearance length
d4 = represents the distance travelled by an opposing vehicle at the design speed
while the overtaking manoeuver is taking place
d1 d2 d3 d4
Figure : Elements of Overtaking Sight Distance for two-lane highway
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d1 = vb t
s = (0.2 vb + 6)
d2 = (vb T + 2s)
d3 = vT
d4 = 2/3 (d2)
OSD = (d1 + d2 + d3 + d4)
= (d1 + 5/3d2 + d3 )
Therefore
OSD = 0.278 vb t +5/3(0.278vb T + 2s)+0.278VT
Where, vb = speed of overtaken vehicle, kmph
t = reaction time, sec,
V = speed of overtaking vehicle or design speed, kmph
T = √14.4s/A,sec = time taken for overtaking operations = spacing of vehicles = (0.2 vb + 6)
A = acceleration, kmph/sec
If the speed of overtaken vehicle vb is not given, the speed of overtaken
vehicle may be assumed as vb = (V – 16) kmph
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Minimum overtaking distance
For two-way traffic = (d1 + d2 + d3 + d4)
For one-way traffic = (d1 + d2)
On divided highway with four or more lanes, IRC suggests that normal OSD
is not necessarily be provided, only sight distance may be ensured which
should be more than the required SSD, which is absolute minimum sight
distance
OVERTAKING ZONE
The zones where the overtaking opportunity is available, zones which are
meant for overtaking.
The minimum length of overtaking zone:
For two-way traffic = 3 (d1 + d2 + d3 + d4)For one-way traffic = 3(d1 + d2)
The desirable length of overtaking zone is five times of the overtaking sight
distance
Speed Intermediate Sight
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Table: Overtaking Sight Distance as Per
IRC
Speed (Km/hr)Safe overtaking Sight
distance (m)
40 165
50 235
60 300
65 340
80 470
100 640
Table: Intermediate Sight Distance
Speed
(Km/hr)
Intermediate Sight
distance (m)
20 40
25 50
30 60
40 90
50 120
60 160
65 180
80 240
100 360
For the section of road where the overtaking sight distance can not be provided, as a
second preference, intermediate value between the safe SSD and safe OSD is
recommended
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Set-Back distance at obstructions of horizontal curve
The Value of Set-back distance M = S2 /8R
(for cases where the required sight distance is wholly within the curved road)
Figure: Elements of Set-Back distance at obstructions of horizontal curve
S
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R
mn
S
Sight Obstruction
SIGHT LINE
Fig. Visibility of Horizontal curve
R = radius of curve
S = Sight distance
m = minimum set- back distance
n = distance between centre line of
carriageway and centre line ofinside lane
Centre line of
carriage wayCentre line of
inside lane
Ref: IRC : 73-1980
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CALCULATION OF SET-BACK DISTANCE
The set-back distance is calculated from the following equation
m = R – (R-n) Cos
Where = [S / 2(R-n)] radians;
m = the minimum set-back distance to sight obstruction in meters
(measured from centre line of the road);
R = radius of centre line of the road in meters;
n = distance between the centre line of the road and the centre line of
the inside lane in meters; and
S = sight distance in meters
In the above equation, sight distance is measured along the middle of inner lane.
On single-lane roads, sight distance is measured along centre line of the roadand ‘n’ is taken as zero
Set-back distance for overtaking or intermediate sight distance can be computed
similarly but the clearance required is usually too large to be economically
feasible except on very flat curve
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Horizontal Alignment
Design of horizontal alignment consists of the following aspects such as
Design Speed
Horizontal CurveSuper elevation
Widening of pavement on horizontal curve
Horizontal Transition Curve
Design Speed
Design speed is a speed determined for design and correlation of the physical
features of a highway that influence vehicle operation. It is the maximum safe
speed that can be maintained over a specified section of a highway when
conditions are so favourable that the design features of the highway govern. The
design speed must be correlated with the terrain conditions as well as the
classification of highways.
The 95th and 98th percentile speed are frequently chosen at the Design Speed
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Horizontal Curve
A horizontal highway curve is a curve in plan to provide change in direction to the
central line of a road
The horizontal curve consists of
Horizontal Circular Curve
Horizontal Transition Curve
COMBINED CIRCULAR AND TRANSITION CURVE
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Superelevation
When a vehicle is moving on a curved path, it is subjected to an outward force,
commonly known as the centrifugal forces. In order to resist this forces, it is the usual
practice to super-elevate the roadway cross-section
The expression for super-elevation,
e + f = V2/ 127R,
V = Km/hr
R = Radius of the curve, m
e = super elevation, max value is 0.07 for plain and rolling terrain, for hill road notbounded by snow, max value is 0.10
f = Co-efficient of lateral friction, max value is 0.15
Coefficient of lateral friction depends on:
o Vehicle Speed
o Type and condition of road surface
o Type and condition of tyre
IRC suggested max value of f is 0.15
AASHTO suggested a max value of 0.16 for speed 50 kmph and min value of 0.08
for 120 kmph
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Equivalent Super elevation
Considering co-efficient of lateral friction = 0,
e = V2/127R,
In this condition pressure under both the wheel (inner and outer) will be same
As per the Indian practice, super-elevation is calculated on the assumption that it should
counteract the centrifugal force developed at three-fourth of design speed. Thus
e = (0.75V)2/127R
= V2/225R
Calculation for Super elevation
Step 01: Calculate the super elevation for 75% of design speed neglecting friction
Step 02: If calculated value of e is less than 0.07 for plain and rolling terrain, the value so
obtained is provided,If the value of e exceeds 0.07 then provide max super elevation of 0.07 and go
to step 03
Step 03: Check the co-efficient of friction developed for the max value of e (e=0.07) at
the full value of design speed, f = (V2/127R – 0.07)
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if the value of f comes less than 0.15 the super elevation of 0.07 is safe for the design
speed
If not, calculate the restricted speed as given in step 04
Step 04: As an alternate to step 04 the allowable speed at the curve is calculated byconsidering the design co-efficient of lateral friction and the max value of e
e + f = 0.07 + 0.15 = V2/127R
Note:
Appropriate warning sign and speed limit regulation sign are installed to
restrict and regulate the speed at such curves where the safe allowable
speed is less than the design speed
For highways the curve should be designed without any speed restriction
Therefore the curve should be re-aligned for the curve maintained design
speed.
Radaii curves for which no super-elevation is required
The normal camber can be provided for the section where the super elevation
calculated is less than the camber
R = V2/225 e
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Practical Values of the super-elevation rate
The value of the super-elevation rate that can be used is dependent on many factors:
o The frequency of snowfall (in cold countries)
o The type of terrain
o The type of area (urban or rural)
o Frequency of slow moving vehicles
Considering the factors various codes suggested different maximum levels of super-elevation rate
Consider a stopped vehicle on the curveas shown in the fig, for its equilibrium
condition the following inequality will
satisfy,
mg sin θ ≤ f s, max × mg cos θ
tan θ ≤ f s, maxe < f s, max
f s, max is the maximum co-efficient of
side friction
AASHTO suggested, for low speed,
maximum friction value close to 0.3,
where as IRC suggest a value of 0.15
Fig. Free body diagram of a static
vehicle on a circular horizontal curve
mg sin θ
f s × mg cos θ
mg cos θ
mg
θ
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Practical Values of the super-elevation rate
AASHTO suggested, for low speed, maximum friction value close to 0.3
IRC suggests a value of side friction as 0.15, which is independent of speed. Thisindicates that the maximum value of e, (i.e. emax), that can be used is at least as high
as 0.15.
However the practical maximum limits of e, as suggested by IRC and AASHTO, are
much lower than this value.
AASHTO suggests using e values less than 0.1 with several other lower limiting values
which depend on the terrain and environmental factors.
IRC (IRC: 73 – 1980, IRC:86 -1983) suggests the following maximum limits on e
values:
For plain and rolling terrain and snow bound areas – 0.07
For hilly terrains (without snow) – 0.1
For urban roads with frequent intersection – 0.4
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ATTAINMENT OF SUPERELEVATION ON CIRCULAR CURVE
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Widening of pavement on horizontal curve
On horizontal curves, especially when they are not of large radii, it is common to
widen the pavement slightly more than the normal width. That is some extra width
has been introduced at the horizontal curve. This method is referred as extra
widening of pavement.
Causes:
The vehicle has rigid wheel base and only front wheels can turn, the rear
wheel do not follow the same path as that of the front wheels.
When the vehicle operating the speed higher than the design speed, the
super-elevation and the friction of the pavement can not fully counteract thecentrifugal force effect. In that case some transverse skidding may occur.
Therefore in that situation extra widening is necessary.
While overtaking at horizontal curve there is the tendency of the driver to
maintain a greater lateral clearance between two vehicles than on straight
path for ensuring safety.The extra width of the pavement on horizontal curve is depend upon
1. Length of the wheel base of the vehicle
2. Radius of horizontal curve negotiating
3. Psychological factor depending on speed and radius of curve
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The extra widening of pavement on horizontal curves is divided into two parts:
Mechanical widening – W m Psychological widening – W ps
Mechanical widening
The widening required to account for the off-tracking due to the rigidity of wheel
base is referred as mechanical widening ( W m ) and can be calculated as given
below:
W m = l 2 / 2R
Where, l = Length of wheel base, m.
R = Radius of horizontal curve, m
The mechanical widening calculated above is required for one vehicle negotiating a
horizontal curve along one traffic lane.Hence in a road having ‘n’ traffic lanes, as ‘n’ vehicles can travel simultaneously, the
total mechanical widening required is given below:
W m = n l 2 / 2R
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Table: Extra width of pavement at horizontal curve
Radius of curve (m)Extra width in meter
Single lane Two - laneUp to 20 0.9 1.5
20 to 40 0.6 1.5
41 to 60 0.6 1.2
61 to 100 Nil 0.9
101 to 300 Nil 0.6
Above 300 Nil Nil
For multi-lane roads, the extra widening is calculated by adding half the extra
width of two lane roads to each lane of multilane road
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Method of introducing extra widening on horizontal circular curve
The widening is introduced gradually from the beginning of the transition curve with
an uniform rate till the full value of designed extra width is reached at the end of thetransition curve where full value of super-elevation is also provided
The full value of designed extra width is continued throughout the circular curve and
decreased along the transition curve
Normally the extra width is equally distributed i.e., We /2 each on inner and outer sides of the curve
On sharp curves of hill roads the extra widening in full may be provided on inside of
the curve
On horizontal circular curve without transition curves, two-thirds of the designed extra
width is provided at the end of the straight section, i.e., before the start of the circular
curve and the remaining one-third is provided on the circular curve
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Horizontal Transition Curve
NEED FOR TRANSITION CURVE (Introduction)
When a vehicle traveling on a straight course enters a curve of finite radius it is
suddenly subjected to the centrifugal force which causes jerk/shock and sway. In
order to avoid this it is customary to provide a transition curve at the beginning of
the circular curve having a radius equal to infinity at the end of the straight and
gradually reducing the radius to the radius of the circular curve where the curve
begins. Incidentally, the transition portion is also used for the gradual application of
the super elevation and the curve widening
OBJECTIVE OF PROVIDING TRANSITION CURVE
1. Gradually introducing the centrifugal force effect
2. For easy streeting of driver on the curve with safety & comfort
3. To provide super-elevation gradually
TYPES OF TRANSITION CURVE
# Spiral OR Clothoid
# Lemniscates
# Cubic parabola
111
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111
Normally Transition curve are of Spiral or Clothoid
IRC recommends the use of spiral as transition curve in horizontal alignment as
the
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Design standards for vertical curves establish their minimum lengths for
specific circumstances. For highways, minimum length of vertical curve may
be based on sight distance, on comfort standards involving vertical
acceleration, or appearance criteria
Vertical curves are normally parabolas centered about the point of
intersection (P.I.) of vertical tangents they join
The parabola is selected as the vertical curve so that the rate of change of
grade, which is the second derivative of curve, will be constant with
distance.
H Hh
Length of summit curve
OSD
SSD
N = (n1 + n2)
+n1 -n2
Fig. Length of summit curve
P.I.
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Length of summ it curve for stopping s ight distance (SSD)
Two cases are to be considered in deciding the length:
1. When the length of curve is greater than the sight distance (L > SSD)
2. When the length of curve is less than the sight distance (L < SSD)
When L > SSD
The general equation for length L of the parabolic curve is
L =
Where,
L = Length of summit curve, m
S = Stopping sight distance, m
N = Deviation angle, equal to algebraic difference in grades
H = Height of eye level of driver above roadway surface, 1.2 m.
h = Height of object above the pavement surface, 0.15 m.
2)2h2H(
2 NS
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When L < SSD
The general equation for length L of the parabolic curve is
L = 2S -
Where,
L = Length of summit curve, m
S = Stopping sight distance, m
N = Deviation angle, equal to algebraic difference in grades
H = Height of eye level of driver above roadway surface, 1.2 m.
h = Height of object above the pavement surface, 0.15 m.
N
2)2h2H(
Length of summ it curve for safe overtaking s ight d istance (OSD)
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Length of summ it curve for safe overtaking s ight d istance (OSD)
or Intermediate sight dis tance
Two cases are to be considered in deciding the length:
1. When the length of curve is greater than the overtaking sight distance or
Intermediate sight distance (L > S)
2. When the length of curve is less than the overtaking sight distance or
Intermediate sight distance (L < S)
When L > S
L = NS2/ 8H ; substituting h = H
When L < S
L = 2S – 8H/N
Example of typical vertical alignment
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Example of typical vertical alignment
I.P.
I.P.Up hill
straight linegradient (+ve)
Crest/Summit
curve (Parabola)
Downhill
straight line
gradient (-ve)
Sag/Valley curve(Parabola)
Up hill
straight linegradient (+ve)
Fig. Typical vertical alignment
Valley curve
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Valley curve
The length of valley curve is designed based on two important consideration
1. Impact free movement of vehicles at design speed or comfort criteria
of the passenger
2. Availability of SSD under head lights of vehicles for night driving
The best shape of valley curve is a transition curve for gradually
introducing and increasing the centrifugal acceleration or radial
acceleration change acting downward as the allowable rate of change
of centrifugal acceleration govern the design of valley curve
Allowable rate of change of centrifugal/radial acceleration is 0.6 m/s3
Generally Cubic parabola is preferred for vertical valley curve
Length of valley curve
The length of valley curve is design based on two criteria
I. The allowable rate of change of centrifugal/radial acceleration is
0.6 m/s3 that is comfort criteria and
II. The head light sight distance of the vehicle for night driving
The higher of the two value is adopted for design
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The valley curve is made with full transition curve (no circular in between), two similar transition curve of equal length
In fig. Total length of valley curve is L, and length of two similar transition curve is LS = L/2
having minimum radius R at common point on the curve, K
1. Th e len gth o f v alley c urv e fo r c om fo rt c on dit io n is
L = 2 LS = 0.38 (NV3)1/2
Consideration : value of rate of change of centrifugal acceleration is taken as 0.6 m/s3
Where,
N = Deviation angle, equal to algebraic difference in grades
V = Design Speed, kmph
-n1 +n2
Length of valley curve, L
N
L/2 L/2
Fig. Length of valley curve
K
2 Length of valley curve for head light s ight d istance of the vehic le
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2. Length of valley curve for head light sight distance of the vehic le
This can be determined from the two condition
a. When the total length of valley curve L is greater than the stoppingsight distance (equal to head light sight distance of vehicle), L>SSD
b. When L is less than SSD, LSSD
L =)tan22( 1
2
S h
NS
h1 h1
S
N
S tan
Fig. Head light sight distancewhen L > S
Where,
Average Height of the head light, h1 = 0.75
The beam angle = 10
L = Total length of valley curve, m
Where,
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b. When L
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Problem#01
An ascending gradient of 1 in 50 meets a
descending gradient of 1 in 80. Determine
the length of summit curve for a design
speed 80 kmph. Assume all other data
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Problem#02
A valley curve is formed by a descending gradient of 1 in40 which meets an ascending gradient of 1 in 30.
Design the total length of valley curve if the design
speed is 80 kmph so as to fulfill both comfort condition
and head light sight distance for night driving, after calculating the SSD required
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TRAFFIC ENGINEERING
Definition
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Definition
Traffic Engineering, a branch of transportation engineering, is
described as “that phase of transportation engineering which deals with
planning, geometric design, and traffic operations of roads, streets and
highways, their networks, terminals, abutting lands and relationship
with other modes of transportation”.
The study of Traffic Engineering is sub-divided in to the following groupsTraffic Characteristics
Traffic Studies and analysis
Traffic operation – control and regulation
Planning and analysis
Geometric design
Administration and management
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Traffic Characteristics
o Road User Characteristics
o Vehicle Characteristics
Traffic Studies and analysis
Traffic Volume study
Speed Studies
Origin and destination (OD) study
Traffic Flow characteristics
Traffic capacity study
Parking study
Accident study
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Traffic operation – control and regulation
Traffic Planning and analysis
Geometric design
Administration and management
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Traffic Characteristics
Road User Characteristics
Physical Mental Psychological Environmental
Vision,
hearing
Knowledge,
Skill, etc.
Perception, Intellection,
Emotion, and Volition
(PIEVE time)
Atmospheric condition,
locality, traffic
streams
Vehicular Characteristics
Vehicle
Dimensions
Gross vehicle
weight andaxle weight
Power of
vehicle
Speed of
vehicle
Breaking
characteristics
Maximum dimensions of Road Vehicles
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Maximum dimensions of Road Vehicles
Dimension of
vehicle
Details
Maximum Dimensions, m
(excluding front & rear
bumper)
Width All vehicles 2.50
Height
a) Single-decked vehicle for normal
application b) Double-decked vehicle
3.80
4.75
Length
a) Single-unit truck with two or more
axles
b) Single unit bus with two or more
axlesc) Semi-trailer tractor combinations
d) Tractor and trailer combinations
11.00
12.00
16.0018.00
Ref: Dimensions and Weights of Road Design Vehicles, IRC:3 – 1983, Indian
Roads Congress, New Delhi, 1983
Traffic Studies and analysis
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Traffic Studies and analysis
Traffic Volume study
Objective
1. To select the priority for improvement and expansion of trafficfacilities
2. This study helps in planning and design of traffic control
methodology
3. Classified traffic volume count study ( IRC recommends 7days 24
hours for mid block and 16 hours for junction, for rural roads) is
needed for structural design of pavement, finding the capacity of
the roadway etc
4. Turning movement count is used to design the intersection, fixing
the traffic signal timing etc.
5. Pedestrian traffic volume study is used for design side walks or
foot path, pedestrian signal timing, foot over bridge etc.Methods
1. Mechanical counters
2. Manual Methods
Presentation of Traffic Volume Data
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Presentation of Traffic Volume Data
Average Daily Traffic (ADT)
It is the average volume of traffic counted for 7 days 24 hours or 3 days 24
hours (Ref: IRC 64; IRC: 109)
Annual Average Daily Traffic (AADT)
It can be calculated from the traffic survey conducted throughout the year of all
season or by multiplying the ADT with Seasonali ty Facto r
Charts showing hourly, daily and seasonal variation of traffic
Composition of different types of traffic
Flow volume diagrams at an intersection
Thirtieth highest hourly volume Design hourly volume
It is the hourly volume that will be exceeded only 29 times in a year and all
other hourly volume of the year will be less than this value, For Indian
condition design hourly volume (DHV) of 8 to 10% AADT has been suggested
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TRAFFIC COMPOSITION A NATIONAL HIGHWAY
Car / Jeep /Van
17.9%
2 Axle Truck14.6%
Multi Axle Truck
10.3%Bus
7.4%
Cycle Rickshaw2.8%
2 Wheelers
12.2%
Other Fast
0.1%
Bicycle
29.2%
3 Wheelers
5.3%
Agricultural Tractor
0.1%
Other Slow0.0%
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0 20 40 60 80 100 120
10
20
30
40
50
Number of Hours in one year with Traffic Volume Exceeding that shown
H o u
r l yT r af f i cV ol um e– p er c en t of ADT
3 0 T HHI GHE S
T H O UR
Stream flow fundamentals
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Stream flow fundamentals
Definition
Flow: Flow (q) is defined as the number of vehicles passing a specified
point or short section in a given period of time in a single lane. It isexpressed as vehicles/hour/lane
Free-flow speed (uf ) : It is that speed which exists when flows approaches
zero under free-flow condition.
Optimum speed (uO ) : It is that speed which exists under maximum flow
condition.
Density (k) : It is defined as number of vehicles occupying a section of roadway
in a single lane. It is expressed as vehicles/km./lane
Jam density (k j ) : It is that density that occurs when both flow and speed
approaches zero
Optimum density (k O ) : It is occurred under maximum flow condition
Speed, flow and density relationship
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k j
uf
Density
(veh/km)
Speed(km/h)
Flow (veh/hr)
Speed
(km/hr)
q m
u o
uo = Speed at maximum flow qm
Which is half of free-flow speed uf
k j = jam density
km = density at maximum flow qm
uf Speed-density
relationship
Speed-flow
relationship
Flow
(veh/hr/lane)
Density
(veh/km/lane)
k jko
q m
ko
u o
Flow-density
relationship
Speed studies
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p
Spot Speed
It is the instantaneous speed of a vehicle at a specified location
Time-mean speedIt is the average of the speed measurements at one point in space over a
period of the time. It is the average of a number of spot speed
measurements.
Space-mean speed
It is the average of the speed measurements at an instant of time over a
space