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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.
419/04/23
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.
519/04/23
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
619/04/23
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
819/04/23
Lecture 1
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
919/04/23
2 2
braking distance (meters)
initial vehicle speed (kmph)
final vehicle speed (kmph)
friction between tyre and road
grade
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Lecture 1
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
1019/04/23
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
1119/04/23
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Lecture 1
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.
1219/04/23
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
1319/04/23
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Age Groups
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.)
1419/04/23
Lecture 1
Perception/Reaction Time
1519/04/23
Driver Characteristics 2
15
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)
1619/04/23
Driver Characteristics 3
Lecture 1
•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
1819/04/23
Driver Characteristics 5
Lecture 1
Road CharacteristicsGeometric characteristics of road
–Horizontal alignment–Vertical alignment–Other geometric elements (water drainage etc.)–Highway Design (no. of lanes etc.)
1919/04/23
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
2019/04/23
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)
2119/04/23