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8/30/2012
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Traffic Engg andTraffic Engg and Safety
CE-444
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TRAFFIC ENGINEERING & SAFETY
Credit Hours 2 + 1 = 3 (16 weeks)
T t l P i d (32 48) 80Total Periods : (32+48) = 80
Text Book1. Priciples of Highway Engineering and Traffic
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p f g y g g ffAnalysis by Fred L. Mannering, W.P.Kilareski,and S.S.Washburn
2. “Introduction to Traffic Engineering, a manual fordata Collection and analysis” by Thomas R Currin.
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Course Outline Introduction (4)• Typical Transportation/Traffic Issues and Solutions
• Introduction to Traditional Traffic Studies• Introduction to Traditional Traffic Studies
• Modes of Transport
• Traffic Engineering Elements
• Traffic Surveys
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Course Outline Traffic Flow Characteristics (10)(1) Nature of Traffic Flow
(2) Parameters Connected With Traffic Flow( )
(3) Interrupted and Uninterrupted Traffic
(3) Analysis of Speed Flow and Density Relationship
(4) Traffic Stream Characteristics and Models: Flow, Speed, Density
(5) Queuing Theory, Queuing Models and Analysis
(6) Traffic Volume Studies
(7) Highway Level of Service Analysis
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Course Outline Traffic Signals (10)• Basic Concepts of Traffic Signals and Signalized Intersection
• Types Traffic Signals yp g
• Signal Design, Phasing and Timing Plan
• Queuing Theory, Queuing Models and Analysis for Traffic Signals
• Delays at Isolated Traffic Signals
• Level of Service Analysis for Signalized Intersections
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Course Outline Traffic Safety (08)• Introduction
• Traffic Safety Measuresy
• Basics of Highway Safety management
• Highway Safety Analysis
• Traffic Safety Audits and Identification Of Hazardous Location
• Safety Considerations in Highway Design
• Highway Safety Countermeasures
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Course Outline Practicals (48)• Spot speed study
• Turning movement counts / vehicle countsg
• Vehicle delay study
• Saturation flow study
• PHF Study
• Parking study
• Vehicle occupancy study
• Level of Service Analysis for Signalized Intersections
• Highway Level of Service Analysis
• Use of Traffic Analysis and Simulation Software “SYNCHRO”
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Course Outline Term Project
(Weightage; 50 to 60 % of Practical i.e. 1 cr hr) Students are asked to select a topic of their own interestp
within the scope of this course.
Students are required to submit a project report and presenttheir projects at the end of the course.
The term project may include any case study oridentification of a real time traffic or safety problem andrecommended solution.recommended solution.
Due importance is given to learning the procedure tocarryout research and case reporting (preparation of aproject report).
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Grade Distribution
Total - 100Fi l E 34% Final Exam - 34%
Sessional - 66%Assignment - 5% of Sessional
Quiz - 10% of Sessional
Class Test - 35% of Sessional
Practical - 50% of SessionalTerm Project - 50-60% of Practical
Lab Work/Field Exercises - 40–50% of Practical
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Thought of the Day
• Always try your best and be contented on• Always try your best and be contented onwhatever comes to you, because it is thewill of Allah.
• Always believe that whatever ishappening to you in this life is the bestfrom HIM.
• It is only HE who knows the BEST andHE knows ALL.
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Points for Consideration
• Be attentive• Be attentive
• Do not hesitate to ask questions
• Make notes of what is being taught in theclass
• Always bring calculators• Always bring calculators
• Always bring the book/notes
• Follow the rules/instructions
• Always try to be positive11
Present Transportation Issuesand Trends
• What are the current transportation issues?• What are the current transportation issues?– Man-inflicted disasters (security)– Large number of crashes and their severity– Congestion in urban areas– Contribution to environmental pollution
• Where are the solutions?– Security– Congestion management – Safety management – Multimodalism– Intelligent Transportation Systems 12
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Present Transportation Issuesand Trends
• What are the current transportation issues?• What are the current transportation issues?– Man-inflicted disasters (security)– Large number of crashes and their severity– Congestion in urban areas– Contribution to environmental pollution
• Where are the solutions?– Security management– Congestion management – Safety management – Multimodalism– Intelligent Transportation Systems 13
Traffic and safety studies needed for effective congestion and safety management:congestion and safety management:
Traffic generation, Parking demand, Capacity and quality of traffic, Control and geometry improvements,
d h d d id ifi iRoad hazard and countermeasures identification
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What Answers Are Sought?
• Current highway and parking use• Current traffic characteristics• Current traffic characteristics• Current traffic and parking quality• Current highway safety• How to improve current traffic conditions • Impact of new highway projects/improvementsp g y p j p• Impact of a new land development• Future traffic conditions
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Scale of the Studies
• Single facilities (intersection, roadSingle facilities (intersection, road section)
• Arterial streets
• Corridors (several parallel roads)
L l ( t f th t k)• Local areas (part of the network)
• Entire systems (city, province,district)
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Traditional Traffic Studies
• Volume studies• Volume studies• Speed studies• Travel time studies• Delay studies• Density studiesy• Headway and spacing studies• Accident studies
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Special Traffic Studies and Analyses
• Traffic impact studies and analyses• Safety analyses• Safety analyses
– Identification of hazardous locations– Identification of hazard sources– Identification of countermeasures
• Corridor studies• Parking studiesg• Congestion analyses• Pedestrian studies• Before-and-after studies
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Transportation System
• A transportation system is an infrastructure• A transportation system is an infrastructurethat serves to move people and goodsefficiently. The transportation systemconsists of fixed facilities, flow entities, anda control component.
• Efficient
safe, rapid, comfortable, convenient, economical, environmentally compatible. 19
Transportation System
Major transportation subsystemsMajor transportation subsystems
• Land transportation: highway, rail
• Air transportation: domestic, international
• Water transportation; coastal, rivers
Pi li il t• Pipelines: oil, gas, water
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Highway Transportation System
• Fixed facilities: d b id i t ti i t hroads, bridges, intersections, interchanges, s
ervice stations, etc.
• Flow entities: passenger cars, buses, trucks, pedestrians, etc.
• Control component: highwayControl component: highway administration, local transportation agencies (signs, markings, signals)
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Traffic Engineering
• Traffic engineering is that phase of• Traffic engineering is that phase oftransportation engineering which deals withthe planning, geometric design and trafficoperations of roads, streets, and highways,their networks, terminals, and relationshipsbetween different modes of transportation
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Traffic Engineering Traffic studies are carried out to:
Provide a basis for planning and designing traffic Provide a basis for planning and designing traffic
facilities, including the selection of geometric
standards, economic analysis, and the determination
of priorities; assist traffic operation by determining
the need for traffic control devices such as
signs, traffic control signals, pavement
markings, and school and pedestrian crossings
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Traffic Engineering• Traffic Engineering covers a broad range of engineering
application with common focus: the nation’s system ofhighways and streets.
• Often defined as the nation’s “lifeblood circulation system”
– Infrastructure supports the vast majority of people and goods.
– Including economy and the environment, assurance f bli f d iof public safety and security.
– Basic mobility of all societal functions.
– Basic access to the most remote regions.
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Objectives
• Traffic Engineering
“D l i h h S f d Effi i t– “Deals with the Safe and Efficient movementof people and goods on streets and highways”
– Other Objectives• Speed
• Comfort
i• Convenience
• Economy
• Environmental compatibility
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Objectives• Safety:
– The principal goal of the traffic engineeri h i i f f fremains the provision of a safe system for
highway traffic
• Speed: – While speed of travel is very much desired, it is
limited by transportation technology, humancharacteristics and the needs to provide safetycharacteristics, and the needs to provide safety
• Comfort: – Comfort involves the physical characteristics of
vehicles and roadways, and is influenced by ourperception 26
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Objectives
• Environmental compatibility:
– Harmony with the environment is a complex
issue that has become more important over time
– All transportation systems have some negative
impacts on the environmentimpacts on the environment
– All produce air and noise pollution in some
forms, and all utilize valuable land resources27
Road Functions
Mobility
Accessibility28
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• MobilityAbilit t t l t diff t d ti ti
Mobility and Accessibility
– Ability to travel to many different destinations
– Provided by Freeways, Motorways…..
• Accessibility– Ability to gain access to a particular site or area
– Provided by Local StreetsProvided by Local Streets
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Hierarchical Rural
Structure of Road
Networks
Urban
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Mobility vs. Accessibility
Road Class Road Function
Freeways/Motorways Through movement exclusively
Arterials Through movement primary and some land access
Collectors Traffic movement to higher rank roads, access to abutting properties
Local Roads Access to abutting land and local traffic movement
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Mobility vs. Accessibility
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Mobility vs. Transportation Mode
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Mobility vs. Transportation Mode
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Traffic Engineering
Person and Vehicle Movement
How many people may be moved in vehicles of different types How many people may be moved in vehicles of different types
on different types of facilities:
Goods Movement /Freight
Trucks
Vital to Economy
Must be incorporated into Transportation system plans
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Components of Traffic System
Road Users
Drivers
Pedestrians Pedestrians
Bicyclists
Passengers
Vehicles
Private
Commercial Commercial
Street and Highways
Traffic Control Devices
General Environment
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Modes to Transportation
• Urban People Transportation• Urban People-Transportation– Automobile
– Taxi/For-Hire Vehicles
– Bus Transit
– Rail
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Modes to Transportation
• Intercity People Transportation• Intercity People-Transportation– Automobile
– Intercity Bus
– Railroad
– Air
– Water
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Modes to Transportation
• Urban & Intercity Freight Transportation• Urban & Intercity Freight Transportation– Long-Haul Trucks
– Local Trucks
– Railroads
– Water
– Air Freight
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Elements of Traffic Engineering
• Traffic Studies• Traffic Studies
• Facility Design
• Traffic Control
• Traffic Operations
P f E l ti• Performance Evaluation
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Elements of Traffic Engineering• Traffic Studies
I l i d tif i i– Involve measuring and quantifying variousaspect of highway traffic. Studies focus on datacollection and analysis that is used tocharacterize traffic, including (but not limitedto) traffic volumes and demands, speed andtravel time delay accidents origins andtravel time, delay, accidents, origins anddestinations, modal use, and other variables(e.g. safety).
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Elements of Traffic Engineering
• Facility design• Facility design – Involves traffic engineers in the functional and
geometric design of highways and other trafficfacilities.
– Traffic engineers are not involved in thestr ct ral design of high a facilities b tstructural design of highway facilities butshould have some appreciation for structuralcharacteristics of their facilities.
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Elements of Traffic Engineering• Traffic Control
– is a central function of traffic engineers andinvolves the establishment of traffic regulationsand their communication to the driver throughthe use of traffic control devices, such assigns, markings, and signals.
ffi O i• Traffic Operations– Involves measures that influence overall
operation of traffic facilities, such as one-waystreet system, transit operation, and surveillanceand network control systems. 43
Elements of Traffic Engineering• Performance Evaluation
– Is a mean by which traffic engineers can ratethe operating characteristics of individual
ti f f iliti d f iliti h lsections of facilities and facilities as a whole.– Such evaluation relies on measures of
performance quality and is often stated in termsof “levels of service.”
– Levels of service (LOS) are letter grades, fromA to F, describing how well a facility isoperation using specified performance criteriaoperation using specified performance criteria.(A –Excellent; F- undesirable).
– As part of performance evaluation, the capacityof highway facilities must be determined.
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Elements of Traffic Engineering
• Traffic Systems Management (TSM): – involves virtually all aspects of traffic
engineering in a focus on optimizing systemcapacity and operations.
– Specific aspects of TSM include high-occupancy vehicle priority systems, car-poolingprograms, pricing strategies to manage demand,and similar functions.
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Elements of Traffic Engineering• Integration of intelligent transportation
system technologies (ITS):– It refers to the application of modern
tele-communication technology to the operationand control of transportation system.
– Such systems include but not limited toautomated toll-collection systems (E-toll),vehicle-tracking systems, in vehicle GPS andmapping systems, automated enforcement oftraffic lights and speed laws, Variable MessageSigns, etc.
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Who Are Traffic Engineers’ Clients?
• Policy makers• Highway administration
– State/Province– District– CityCity
• Citizens groups • Land developers• Business owners
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Challenges for a Traffic Engineer
• Urban congestion has been a major issue for many
years.
• Given the transportation demand cycle, it is not
always possible to solve congestion problems through
expansion of capacity.
• Traffic engineers therefore are involved in the
development of programs and strategies to mange
demand in both time and space and to discourage
growth where necessary.
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Challenges for a Traffic Engineer
• Growth management is a major current issue. Wheredevelopment will cause substantial deterioration in thepquality of traffic service, either such development willbe disallowed or the developer will be responsible forgeneral highway and traffic improvements thatmitigate these negative impacts.
• Such policies are more easily dealt with in goodeconomic times. When the economy is sluggish, theissue will often be a clash between the desire to reducecongestion and the desire to encourage developmentas a means of increasing the tax base.
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Traffic Flow Characteristics
Basic Concepts
Flow Rate
Spacing
Headway
Speed
Density
Relationships 50
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Flow Rate (q)
The number of vehicles (n) passing some designated roadway
point in a given time interval (t).
q = n / t
Units are typically vehicles / hour
V l Fl t li d Fl i t f hi lVolume: Flow rate generalized . Flow in terms of vehicles per
hour is called volume.
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• Types of Traffic Flows
– Interrupted flow: Traffic flow is interrupted byfixed elements signals railway crossings etc Itfixed elements, signals, railway crossings etc. Itcauses delay.
– Uninterrupted flow: In which flow remainsuninterrupted through out its course, i.e.,freeways, motorway. Roadway geomerty andinteraction between the vehicles cause majorinteraction between the vehicles cause majorinfluence on vehicular movements.
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Spacing
The distance (ft) between successive vehicles in a ( )
traffic stream, as measured from front bumper to front
bumper
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Headway (h)
The time between successive vehicles, as their front ,
bumpers pass a given point.
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Speed
Time mean speed (spot speed)
Arithmetic mean of all instantaneous vehicle speed at a Arithmetic mean of all instantaneous vehicle speed at a
given “spot” on a roadway section
Space mean speed (u)
The mean travel speed of vehicles traversing a roadway
segment of a known distance (d).
Determined on the basis of time to traverse a known/pre-
defined distance.55
Time Mean/Spot Speed
dt
dxv
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Travel Speed/Space Mean Speed
12
12
tt
xxv
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Density (k)
The number of vehicles (n) occupying a given length (l) of
a lane or roadway at a particular instant
Unit of density is vehicles per unit length of road, e.g.vehicles per mile (vpm).
k = n/l
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Microscopic Characteristicsx
First Vehicle Trajectory
S H d
Dis
tanc
e Space Headway s
Time Headway h
d
Time t
Second Vehicle Trajectory
Spot Speed U
Traffic Stream Measures
Microscopic
Time headway and spacing .
Define characteristics specific to pair of vehicles in thestream
Macroscopic
Flow, speed (space mean speed) and density.
Describe the traffic stream as a whole
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Capacity
• Maximum hourly rate of vehicles or persons that can reasonably
be expected to pass a point, or traverse a uniform section of lane
or roadway, during a specified time period under prevailing
conditions (traffic and roadway)
• Different for different facilities (freeway multilane 2 lane rural• Different for different facilities (freeway, multilane, 2-lane rural,
signals)
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Mobility vs. Transportation ModeCapacity
capacity in veh/h =
capacity in veh/h/lane x number of lanes
capacity in persons/h =capacity in persons/h
capacity in veh/h x average vehicle occupancy
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Mobility vs. Transportation ModeCapacity
Persons/hrVehicles/hrFacility6,000 x 1.7 = 10,2002,000 x 3 = 6,000Three-lane urban freeway
2,400 x 1.7 = 4,080800 x 3 = 2,400Three-lane urban arterial
100 x 80 = 8 000One lane of buses 100 x 80 8,000100 x 1 =100
One lane of buses
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Factors Reduce Capacity of Highway
• Alignment
• Commercial Vehicles
• Lane Width
• Grade
• Pedestrians
• Weather Conditions
• Parked Vehicles 64
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Definitions
• Count – number of vehicles/travelers passing a highway spot in a countingpassing a highway spot in a counting period
• Volume – number of vehicles/travelers passing a highway spot per unit time
• Capacity – maximum volume of vehicles/travelers
• Demand – volume not influenced by highway capacity
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Definitions
• Congested flow: A traffic flow condition causedby a downstream bottleneckby a downstream bottleneck.
• Over Saturation: A traffic condition in whichthe arrival flow rate exceeds capacity.
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Definitions
DemandCapacity
VolumeCongestionT
raff
ic I
nten
sity
Time67
Traffic Stream Parameters Traffic Stream Parameters
Average annual daily traffic (AADT). The average 24-hour volume at a given location over a full 365-day year.
Average daily traffic (ADT) The average 24-hour Average daily traffic (ADT). The average 24-hourvolume at a given location over a defined time period lessthan one year.
Average Weekday Traffic (AWT)
Average Annual Weekday Traffic (AAWT)
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AADT EstimationTrends Method
AA
DT
1997 1998 1999 2000 2001 2002 2003 2004 Year69
AADT EstimationGrowth Rate (Factor) Method
Future Volume = Past Volume · (1 + Growth Rate)N
where N = Future Year – Past Year
Example: 1,200 veh/day in 2000, 3% growth rate
Volume in 2004 = 1,200 · (1 + 0.03)2004-2000 = 1,350 veh/day
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“Peak Hour” Volume Hourly Volumes
Daily volumes, while useful for planning purposes,
cannot be used alone for design or operational analysis
purposes. Volume varies considerably over the 24 hours
of the day, with periods of maximum flow occurring
during morning or evening rush hours.
The single hour of the day that has the highest hourly The single hour of the day that has the highest hourly
volume is reffered to as “Peak Hour”. The traffic
volume within this hour is of greatest interest for design
and operational usage.71
“Peak Hour” Volume
The Peak Hour volume is generally stated as a directional
volume (i.e each direction of flow is counted separately).
Highways and controls must be designed to adequately serve
the peak hour traffic volume in the peak direction of flow.
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Directional Distribution• It is equally important to know and collect the data in both the
directions of a carriage way.
• As peak hours seldom occurs simultaneously in both
directions.
• Usually during peak hours the traffic volume in one direction
is 2/3 of the traffic volume in both directions.
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Traffic Stream Parameters Directional Design Hour Volume (DDHV)
AADT’s are converted to a peak-hour volume in the peak
direction of flow. This is referred to as DDHV.
DDHV= AADT*K*D
K= Proportion of daily traffic occuring during the peak hour
(often during the 30th peak hour of the year).
D= Proportion of peak hour traffic traveling in the peak
direction of flowdirection of flow.
Factors K & D are based upon local or regional
characteristics at existing locations.
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30th Highest Hourly Volume• It is uneconomical to attach too much importance to the
exceptionally high peaks of traffic volume which occur ononly a few occasions throughout the year.
• So particularly we never design a carriage way to be• So, particularly we never design a carriage way to becongestion free every hour through out the year.
• In practice the traffic volume varies from hour to hour.
• This volume tends to be stable for a given road and is thevolume for which the ratio of benefit and expenditure (cost)is near the maximum.
• Roads are designed to carry this volume.
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Traffic Stream Parameters Peak Hour Factor (PHF)
The relationship between hourly volume and the maximumrate of flow within the hour is defined as PHF asrate of flow within the hour is defined as PHF as
PHF = hourly volume / max rate of flow
For standard 15 min analysis period,
PHF = V / 4*Vm15
PHF generally varies between 0.7 (for rural) -0.98 (denseurban areas). Can be used to estimate a max flow rate withinan hr based on the full hr-volume.
Max rate of flow within the hr, v=V (hourly vol) / PHF
(v & V in veh / h)
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Peak Hour Factor
Estimation of PHF
PHF = Hourly Count/(4xHighest 15-min Count)
PHF = Hourly Count/(12xHighest 5-min Count)
Use of PHF
Peak Volume Rate = Hourly vol /PHF
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PEAK HOUR AND PEAK HOUR FACTOR-EXAMPLE
Time Flow/5 Min9:00 9:05 1009:05 9:10 809:10 9:15 909:15 9:20 1009:20 9:25 1009:25 9:30 100
250
300
PHF
9:25 9:30 1009:30 9:35 1009:35 9:40 2009:40 9:45 2449:45 9:50 2509:50 9:55 220
9:55 10:00 20010:00 10:05 10010:05 10:10 10010:10 10:15 10010:15 10:20 10010 20 10 25 90
50
100
150
200
Veh
Cou
nt
10:20 10:25 9010:25 10:30 8710:30 10:35 8510:35 10:40 8510:40 10:45 8310:45 10:50 8010:50 10:55 7810:55 11:00 69
0
Time
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PEAK HOUR AND PEAK HOUR FACTOR-EXAMPLE
• Largest 12 consecutive 5 min periods (60 Min) From 9:15 to 10:15
• PEAK HOUR VOLUME = 1814 vph
• Largest 15 min volume within the peak hour is =• Largest 15 min volume within the peak hour is = 244+250+220 = 714 vehicles
• Max Flow Rate = 4 x 714 = 2856 vph
• Peak hour factor =PHF= peak hour volume/max flow rate
• =1814/2856 =0.64
• PHF is a measure of peaking (variation) within one hour.p g ( )
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PEAK HOUR AND PEAK HOUR FACTOR-EXAMPLE
• Largest 12 consecutive 5 min periods (60 Min) From 9:15 to 10:15
• PEAK HOUR VOLUME = 1814 vph
• Largest 5 min volume within the peak hour is 250 vehicles• Largest 5 min volume within the peak hour is 250 vehicles
• Max Flow Rate ( 250/5)*60=3000 vph
• Peak hour factor =PHF= peak hour volume/max flow rate
• =1814/3000 =0.60
• PHF is a measure of peaking (variation) within one hour.
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