Transportation EngineeringLecture 1: Introduction

Dr. Bidisha Ghoshbghosh@tcd.ie

Lecture 1 219/04/23

Syllabus

Traffic Engineering

Transport & Environment

Transport & Energy

Lecture 1 319/04/23

Reference Material

Some of the material for this lecture is taken from http://www.ctre.iastate.edu/, course CE 453 Lecture 7

Lecture 1

Transportation EngineeringThe definition by Institute of Transportation Engineers (ITE) :

Transportation engineering is the application of technology and scientific principles to the planning, functional design, 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.

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Lecture 1

Traffic Engineering•Transport or transportation is the movement of people and goods from one location to another.

•Transportation is necessary as there is a spatial distribution of activities & resources.

•Spatial characteristics generate demand for transport.

•To fulfil the demand there are different modes of transport.

•Most predominant is road transport.

Traffic engineering is that phase of transportation engineering which deals with the planning, geometric design and traffic operations of roads, streets, and highways, their networks, terminals, abutting lands, and relationships with other modes of transportation.

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Lecture 1

Primary Objectives:1. The principal objective of traffic

engineering is to provide a safe system for road traffic including pedestrians and bicycles.

2. Provision of efficient management & operations of road transport network

3. Other objectives can be:

– Sustainability– Environmental impacts – Comfort & convenience of the

user – Economy

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Lecture 1 719/04/23

Traffic SystemComponents:

1. Cars, Buses, Trucks, Taxis --- Vehicular Traffic

2. Motorway, Highway, Urban Arterial, Rural roads --- Road Conditions

3. Young, Drunk, Experienced, Learner’s License --- Driver Characteristics

4. Rainy, Sunny, Foggy, Night-time conditions --- Environmental Conditions

5. Signalised/Unsignalised --- Control Devices

Lecture 1

Vehicle CharacteristicsDimension

–For road design it is important to have design vehicles having dimensions representative of actual fleet

Acceleration performance–The weight-to-power ratios vary significantly for vehicles

Braking Performance–Depends on a tire conditions & type, road surface type & condition, and the slope/grade of the road–Important to calculate safe stopping distance

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Vehicle CharacteristicsBraking Performance

Friction is a function of pavement condition (wet, icy), tire, and roadway surface

Grade is expressed as a decimal.

Frication + grade together determines the deceleration

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braking distance (meters)

initial vehicle speed (kmph)

final vehicle speed (kmph)

friction between tyre and road

grade

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Vehicle CharacteristicsSight DistancesDistance a driver can see ahead at any specific time

Must allow sufficient distance for a driver to perceive/react and stop, swerve etc when necessary

Different types of sight distances,• Stopping• Decision• Passing• Intersection

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Lecture 1

Safe Stopping Distances Stopping sight distance (SSD)It is the length of roadway that should be visible ahead of you, in order to ensure that you will be able to stop if there is an object in your path.  It is composed of two distances,

–Distance traveled during perception/reaction time –Distance required to brake the vehicle

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Vehicle CharacteristicsDecision Sight DistanceWhen situation is unexpected or driver must make unusual maneuvers or under difficult-to-perceive situations. It does not depend on stopping but on manoeuvring safely and efficiently.

Passing Sight DistanceIt is the length of roadway that the driver of the passing vehicle must be able to see initially, in order to make a passing manoeuvre safely.

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Lecture 1

Driver Characteristics 1Variable driver typesAge, gender, physical condition (people with disability, alcohol, etc.), mental capabilities, skill (self perception of the skill level !!), attitude

Overall it can be considered that there is a wide range of users of the road transport facilities

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Lecture 1

How to address variability in driver characteristics?

Most traffic engineering designs are based on a single characteristics value that can safely accommodate majority of driving population.

An 85th percentile value is chosen for most user related parameters (say, braking reaction time, walking speed etc.)

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Lecture 1

Perception/Reaction Time

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Driver Characteristics 2

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PIEV

•PerceptionSees or hears situation (sees deer)

•IdentificationIdentify situation (realizes deer is in road)

•EmotionDecides on course of action (swerve, stop, change lanes, etc)

•Reaction (volition)Acts (time to start events in motion but not actually do action)

Foot begins to hit brake, not actual deceleration

Lecture 1

Perception/Reaction TimeRange: 0.5 to 7 seconds

•Environment: Urban vs. Rural/Night vs. Day/Wet vs. Dry•Age•Physical Condition: Fatigue/Drugs/Alcohol•Distractions

•medical condition

•visual acuity

•ability to see (lighting conditions, presence of fog, snow, etc)

•complexity of situation (more complex = more time)

•complexity of necessary response

•expected versus unexpected situation (traffic light turning red vs. dog darting into road)

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Driver Characteristics 3

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• 85th percentile driver’s reaction time

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Driver Characteristics 4

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•Visual Acuity: Ability to see fine detailsStatic (stationary objects such as

letters) Dynamic (ability to detect moving

objects)

•Depth perception

•Glare recovery

•Peripheral vision

– Key criteria in determining placement of traffic signs

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Driver Characteristics 5

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Road CharacteristicsGeometric characteristics of road

–Horizontal alignment–Vertical alignment–Other geometric elements (water drainage etc.)–Highway Design (no. of lanes etc.)

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Lecture 1

Traffic ControlTraffic Control DevicesTo be effective, a device must,

1. Fulfil a specific purpose2. Command attention3. Convey a clear simple meaning4. Command respect of road users5. Give adequate time for proper response

Broad Category of Traffic Control Devices,– Traffic Marking– Traffic Signs – Traffic Signals

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Lecture 1

Traffic Control DevicesTraffic Markings,

– Longitudinal Markings– Transverse Markings – Object Markings and delineators– Word/ Symbol Markings, – Intersection Markings

Traffic Signs,– Regulatory Signs– Warning Signs– Guide Signs

Traffic Signal Control (covered in details in SS year)

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