Intro Traffic CE20103 [Compatibility Mode]
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Transcript of Intro Traffic CE20103 [Compatibility Mode]
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8/3/2019 Intro Traffic CE20103 [Compatibility Mode]
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Indian Institute of Technology, Kharagpur
Transportation Engineering
Dr. Bhargab Maitra
epar men o v ng neer ngIndian Institute of Technology Kharagpur
Email: [email protected]
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Indian Institute of Technology, Kharagpur
Introduction
which deals with the safe and efficient movementof eo le and oods on streets and hi hwa s
Defined by ITE as that phase of transportationen ineerin which deals with lannin eometricdesign and traffic operations on roads, streetsand highways, their networks, terminals, abutting
an s an re a ons ps w o er mo es otransportation
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Person Movement or Vehicle Movement
Real concern: Movin eo le and oods.
Movement of vehicle is just a way ofaccomplishing this
Useful to appreciate mode of transport and type of
roadway used for moving people and goods
- Effect of mode type
-- Effect of mix of traffic
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Goods Movement and Person Movement
are problematic elements?
Transportation of raw material and finished
r
Goods movement and person movement: Both are
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Mix of Vehicle in Person Movement
In the context of traffic en ineerin the focus is
on movements on streets and highways (excludingrail, air, water transportation, etc.)
Within and between cities and town people
normally move in a mix of- r va e ve c e
- Bus
-- Bicycle, etc.
eterogeneous tra c env ronment preva ng n
developing countries
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Components of Traffic System
Vehicles
or no control
Roadways
Control devices
Traffic Engineers have more
control
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Road Users
Human elements separate traffic engineering from
most other engineering: drivers, passengers,pedestrians, bicyclists, etc.
Several critical characteristics of road users are
quantifiable and can be taken into account in
- Perception and reaction time
- Visual acuity (Static and Dynamic)
- Other driver characteristics like hearing andpsyc o og ca actors. es gn s ou account
for driver characteristics
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- Pedestrian Characteristics: Traffic engineeringis not limited to consideration of motorists and
.
users of highway system like pedestrians.
Pedestrian signals wherever necessary
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Vehicles
Hi hwa s stems accommodate a wide variet of
sizes and types of vehicleDesi n vehicles
Selected motor vehicle: weight, dimensions ando eratin characteristics
Design vehicles are used to determine a variety ofeometric features of hi hwa such as lane
width, extra widening on curves, minimumcorner radius, clearance height, etc.
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Acceleration performance of vehicles
than passenger cars
types of vehicle is a major cause of inefficiency in
mixed traffic streams
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Braking performance of vehicles
performance characteristic of vehicles is brakingor deceleration
Time and distance required to stop a vehicle is a
primary consideration in almost every aspects oftra c system es gn an operat on
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Roadways
Functional classification
Highway facilities are classified by the relativem n f hr h r ffi m v m n n l n
access service they provide
- Cross section elements
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- Vertical alignment
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Traffic Control Devices
Communication of traffic laws and regulations to
drivers by means of control device- Road markings
- Traffic signs
- Traffic signals As control devices are the only measures of
transmitting operational rules to drivers, they must
e c ear, eas y nterprete an comman ng oattention
egu a ory aspec s o ra c con ro mus e
enforced
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Traffic streams: Individual drivers and vehicles
Traffic Stream Characteristics
interact in unique ways with each other and withelements of roadway environment
Traffic stream in quantitative term (key parametersand their measurements): understand the inherent
Analysis, evaluation and improvement: keyr m r n m r m n n n rm l
ranges of behavior
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Traffic Facilitiesa) Uninterrupted-flow Facilities
No external factors to cause periodicinterruptions to the traffic stream: Traffic signals,STOP or YIELD signs, uncontrolled access, etc.
Such facilities include freeways and other limitedaccess roads, long sections of rural highwaysbetween signalized intersections, etc.
ream c arac er s cs epen on n v uavehicles, geometric and general environment of
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b)Interrupted-flow Facilities
devices like traffic signals, STOP or YIELD signs
enters as a significant parameter affecting flow
Constant sto in and restartin of traffic streams
Flow occurs in platoons: A group of vehiclesmovin alon a facilit to ether with si nificant
gaps between two successive groups
Dispersion of platoon: An important consideration
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Traffic Stream Parameters
b) Traffic Volume/Flow Macrosco ic measures
c) Density
,to the traffic stream as a whole
ea way- Microscopic measureApplicable to individual pairs of vehicles within ara c s ream
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a) Speed Distance traveled in unit time: may vary widely
v u v u
geometric features, traffic condition, time, place,
b) Traffic volume / Flow
roadway during unit time. Traffic volume isexpressed as vehicle/h or vehicle/day
c) Density (K)Number of vehicle occu in a unit len th ofroadway at a given instant, usually expressed asvehicles per km
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d) Headway
S ace headwa s :Distance between fronts of
successive vehicles in metersTime headway (h): Time interval between thepassage of the fronts of successive vehicles at a
specified point. It is measured in seconds. It is
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Passenger Car Equivalency (PCE)
Highway Capacity Manual (HCM) defines PCE as
The number of passenger cars that are displacedby a single heavy vehicle of a particular type under",
PCE is also defined as the number of passenger
vehicle of a given type under a prevailing roadway,traffic and control condition
PCE: Static or Dynamic?
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Factors affecting PCE
, , ,
braking characteristics etc.
vehicles: function of speed, driver characteristics,
etc. Traffic composition, speed distribution, volume to
capacity ratio etc.
Roadway characteristics: gradient, curves, accesscontrol, rural or urban road, presence of
, , .
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Traffic control and regulation: one way traffic,speed limit, different traffic control devices, etc.
Typical PCE values for Indian Rural Road
nv ronmenta an c mat c con t on
Vehicle Type PCE
Passenger car, tempo, auto 1.0Bus, truck, agricultural tractor-trailer unit 3.0
Motor cycle, scooter, cycle 0.5
Cycle rickshaw 1.5
Horse drawn vehicles 4.0
Small bullock cart 6.0
Large bullock cart 8.0