intro traffic ce20103 [compatibility mode]

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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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

-

- 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

intro traffic ce20103 [compatibility mode]

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