traffic engineering study TES
Content
8/30/2012
Traffic Engg and Safety CE-444
1
TRAFFIC ENGINEERING & SAFETY
Credit Hours 2 + 1 = 3 (16 weeks) Total P i d (32 48) T t l Periods : (32+48) = 80
Text Book
1. Priciples of Highway Engineering and Traffic p f g y g g ff Analysis by Fred L. Mannering, W.P.Kilareski, and S.S.Washburn 2. “Introduction to Traffic Engineering, a manual for data Collection and analysis” by Thomas R Currin. 2
1
8/30/2012
Course Outline
Introduction
• • • • •
(4)
Typical Transportation/Traffic Issues and Solutions Introduction to Traditional Traffic Studies Modes of Transport Traffic Engineering Elements Traffic Surveys
3
Course Outline
Traffic Flow Characteristics
(1) ( ) (2) (3) (3) (4) (5) (6) (7)
(10)
Nature of Traffic Flow Parameters Connected With Traffic Flow Interrupted and Uninterrupted Traffic Analysis of Speed Flow and Density Relationship Traffic Stream Characteristics and Models: Flow, Speed, Density Queuing Theory, Queuing Models and Analysis Traffic Volume Studies Highway Level of Service Analysis
4
2
8/30/2012
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
5
Course Outline
Traffic Safety
•
(08)
• • • • • •
Introduction y Traffic Safety Measures Basics of Highway Safety management Highway Safety Analysis Traffic Safety Audits and Identification Of Hazardous Location Safety Considerations in Highway Design Highway Safety Countermeasures
6
3
8/30/2012
Course Outline
Practicals
• • • • • • • • • •
(48)
Spot speed study Turning movement counts / vehicle counts g 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”
7
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 interest p within the scope of this course. Students are required to submit a project report and present their projects at the end of the course. The term project may include any case study or identification of a real time traffic or safety problem and recommended solution. Due importance is given to learning the procedure to carryout research and case reporting (preparation of a project report).
8
4
8/30/2012
Grade Distribution
Total 100
34% 66%
5% of Sessional 10% of Sessional 35% of Sessional 50% of Sessional
50-60% of Practical 40–50% of Practical
Fi l E Final Exam Sessional Assignment Quiz Class Test Practical
Term Project Lab Work/Field Exercises -
9
Thought of the Day
• Always try your best and be contented on whatever comes to you, because it is the will of Allah. • Always believe that whatever is happening to you in this life is the best from HIM. • It is only HE who knows the BEST and HE knows ALL.
10
5
8/30/2012
Points for Consideration
• Be attentive • Do not hesitate to ask questions • Make notes of what is being taught in the class • Always bring calculators • Always bring the book/notes • Follow the rules/instructions • Always try to be positive 11
Present Transportation Issues and Trends
• 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 Security Congestion management Safety management Multimodalism Intelligent Transportation Systems
• Where are the solutions?
12
6
8/30/2012
Present Transportation Issues and Trends
• 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 Security management Congestion management Safety management Multimodalism Intelligent Transportation Systems
• Where are the solutions?
13
Traffic and safety studies needed for effective congestion and safety management:
Traffic generation, Parking demand, Capacity and quality of traffic, Control and geometry improvements, Road hazard and countermeasures identification dh d d id ifi i
14
7
8/30/2012
What Answers Are Sought?
• • • • • • • • Current highway and parking use Current traffic characteristics Current traffic and parking quality Current highway safety How to improve current traffic conditions p g y projects/improvements p Impact of new highway p j Impact of a new land development Future traffic conditions
15
Scale of the Studies
• Single facilities (intersection, road section) • Arterial streets • Corridors (several parallel roads) • L l areas (part of the network) Local ( t f th t k) • Entire systems (city, province,district)
16
8
8/30/2012
Traditional Traffic Studies
• • • • • • • Volume studies Speed studies Travel time studies Delay studies y Density studies Headway and spacing studies Accident studies
17
Special Traffic Studies and Analyses
• Traffic impact studies and analyses • Safety analyses
– Identification of hazardous locations – Identification of hazard sources – Identification of countermeasures
• • • • •
Corridor studies g Parking studies Congestion analyses Pedestrian studies Before-and-after studies
18
9
8/30/2012
Transportation System
• A transportation system is an infrastructure that serves to move people and goods efficiently. The transportation system consists of fixed facilities, flow entities, and a control component. • Efficient safe, rapid, comfortable, convenient, econo 19 mical, environmentally compatible.
Transportation System
Major transportation subsystems • Land transportation: highway, rail • Air transportation: domestic, international • Water transportation; coastal, rivers • Pi li Pipelines: oil, gas, water il t
20
10
8/30/2012
Highway Transportation System
• Fixed facilities: roads, bridges, intersections, interchanges, s d b id i t ti i t h ervice stations, etc. • Flow entities: passenger cars, buses, trucks, pedestrians, etc. • Control component: highway administration, local transportation agencies (signs, markings, signals)
21
Traffic Engineering
• 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, and relationships between different modes of transportation
22
11
8/30/2012
Traffic Engineering
Traffic studies are carried out to: 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
23
Traffic Engineering
• Traffic Engineering covers a broad range of engineering application with common focus: the nation’s system of highways 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 of public safety and security. f bli f d i – Basic mobility of all societal functions. – Basic access to the most remote regions.
24
12
8/30/2012
Objectives
• Traffic Engineering – “D l with the S f and Effi i t movement “Deals i h h Safe d Efficient
of people and goods on streets and highways” – Other Objectives
• • • • • Speed Comfort Convenience i Economy Environmental compatibility
25
Objectives
• Safety:
– The principal goal of the traffic engineer remains the provision of a safe system f i h ii f f for highway traffic
• Speed:
– While speed of travel is very much desired, it is limited by transportation technology, human characteristics, characteristics and the needs to provide safety
• Comfort:
– Comfort involves the physical characteristics of vehicles and roadways, and is influenced by our perception 26
13
8/30/2012
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 environment – All produce air and noise pollution in some forms, and all utilize valuable land resources
27
Road Functions
Mobility
Accessibility
28
14
8/30/2012
Mobility and Accessibility
• Mobility
– Abilit to travel to many different destinations Ability t t lt diff t d ti ti – Provided by Freeways, Motorways…..
• Accessibility
– Ability to gain access to a particular site or area – Provided by Local Streets
29
Hierarchical Structure of Road Networks
Rural
Urban
30
15
8/30/2012
Mobility vs. Accessibility
Road Class
Freeways/Motorways Arterials Collectors Local Roads
Road Function
Through movement exclusively Through movement primary and some land access Traffic movement to higher rank roads, access to abutting properties Access to abutting land and local traffic movement
31
Mobility vs. Accessibility
32
16
8/30/2012
Mobility vs. Transportation Mode
33
Mobility vs. Transportation Mode
34
17
8/30/2012
Traffic Engineering
Person and Vehicle Movement 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
35
Components of Traffic System
Road Users Drivers Pedestrians Bicyclists Passengers Vehicles Private Commercial Street and Highways Traffic Control Devices General Environment
36
18
8/30/2012
Modes to Transportation
• Urban People Transportation People-Transportation
– – – – Automobile Taxi/For-Hire Vehicles Bus Transit Rail
37
Modes to Transportation
• Intercity People Transportation People-Transportation
– – – – – Automobile Intercity Bus Railroad Air Water
38
19
8/30/2012
Modes to Transportation
• Urban & Intercity Freight Transportation
– – – – – Long-Haul Trucks Local Trucks Railroads Water Air Freight
39
Elements of Traffic Engineering
• • • • • Traffic Studies Facility Design Traffic Control Traffic Operations Performance E l ti P f Evaluation
40
20
8/30/2012
Elements of Traffic Engineering
• Traffic Studies
–I Involve measuring and quantifying various l i d tif i i aspect of highway traffic. Studies focus on data collection and analysis that is used to characterize traffic, including (but not limited to) traffic volumes and demands, speed and travel time delay accidents origins and time, delay, accidents, destinations, modal use, and other variables (e.g. safety).
41
Elements of Traffic Engineering
• Facility design
– Involves traffic engineers in the functional and geometric design of highways and other traffic facilities. – Traffic engineers are not involved in the structural str ct ral design of high a facilities b t highway but should have some appreciation for structural characteristics of their facilities.
42
21
8/30/2012
Elements of Traffic Engineering
• Traffic Control
– is a central function of traffic engineers and involves the establishment of traffic regulations and their communication to the driver through the use of traffic control devices, such as signs, markings, and signals.
• Traffic Operations ffi O i
– Involves measures that influence overall operation of traffic facilities, such as one-way street system, transit operation, and surveillance 43 and network control systems.
Elements of Traffic Engineering
• Performance Evaluation
– Is a mean by which traffic engineers can rate the operating characteristics of individual sections of f iliti and f iliti as a whole. ti f facilities d facilities h l – Such evaluation relies on measures of performance quality and is often stated in terms of “levels of service.” – Levels of service (LOS) are letter grades, from A to F, describing how well a facility is operation using specified performance criteria criteria. (A –Excellent; F- undesirable). – As part of performance evaluation, the capacity of highway facilities must be determined.
44
22
8/30/2012
Elements of Traffic Engineering
• Traffic Systems Management (TSM):
– involves virtually all aspects of traffic engineering in a focus on optimizing system capacity and operations. – Specific aspects of TSM include highoccupancy vehicle priority systems, car-pooling programs, pricing strategies to manage demand, and similar functions.
45
Elements of Traffic Engineering
• Integration of intelligent transportation system technologies (ITS):
– It refers to the application of modern tele-communication technology to the operation and control of transportation system. – Such systems include but not limited to automated toll-collection systems (E-toll), vehicle-tracking systems, in vehicle GPS and mapping systems, automated enforcement of traffic lights and speed laws, Variable Message Signs, etc.
46
23
8/30/2012
Who Are Traffic Engineers’ Clients?
• Policy makers • Highway administration
– State/Province – District – City
• Citizens groups • Land developers • Business owners
47
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.
48
24
8/30/2012
Challenges for a Traffic Engineer
• Growth management is a major current issue. Where development will cause substantial deterioration in the p quality of traffic service, either such development will be disallowed or the developer will be responsible for general highway and traffic improvements that mitigate these negative impacts. • Such policies are more easily dealt with in good economic times. When the economy is sluggish, the issue will often be a clash between the desire to reduce congestion and the desire to encourage development as a means of increasing the tax base.
49
Traffic Flow Characteristics
Basic Concepts Flow Rate Spacing Headway Speed Density Relationships
50
25
8/30/2012
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 Volume: Fl V l Flow rate generalized . Fl t li d Flow i t in terms of vehicles per f hi l hour is called volume.
51
• Types of Traffic Flows – Interrupted flow: Traffic flow is interrupted by fixed elements signals railway crossings etc It elements, signals, etc. causes delay. – Uninterrupted flow: In which flow remains uninterrupted through out its course, i.e., freeways, motorway. Roadway geomerty and interaction between the vehicles cause major influence on vehicular movements.
52
26
8/30/2012
Spacing
The distance (ft) between successive vehicles in a ( ) traffic stream, as measured from front bumper to front bumper
53
Headway (h)
The time between successive vehicles, as their front , bumpers pass a given point.
54
27
8/30/2012
Speed
Time mean speed (spot speed)
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/predefined distance.
55
Time Mean/Spot Speed
v
dx dt
56
28
8/30/2012
Travel Speed/Space Mean Speed
v
x2 x1 t 2 t1
57
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
58
29
8/30/2012
Microscopic Characteristics
Distance x First Vehicle Trajectory Space H d S Headway s
Time Headway h Spot Speed U d Second Vehicle Trajectory Time t
Traffic Stream Measures
Microscopic
Time headway and spacing .
Define characteristics specific to pair of vehicles in the stream
Macroscopic
Flow, speed (space mean speed) and density. Describe the traffic stream as a whole
60
30
8/30/2012
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 (freeway, multilane, 2-lane rural, signals)
61
Mobility vs. Transportation Mode
Capacity capacity in veh/h = capacity in veh/h/lane x number of lanes capacity in persons/h = capacity in veh/h x average vehicle occupancy
62
31
8/30/2012
Mobility vs. Transportation Mode
Capacity Facility
Three-lane urban freeway Three-lane urban arterial One lane of buses
Vehicles/hr
2,000 x 3 = 6,000 800 x 3 = 2,400 100 x 1 =100
Persons/hr
6,000 x 1.7 = 10,200 2,400 x 1.7 = 4,080 100 x 80 = 8 000 8,000
63
Factors Reduce Capacity of Highway
• Alignment • Commercial Vehicles • Lane Width • Grade • Pedestrians • Weather Conditions • Parked Vehicles
64
32
8/30/2012
Definitions
• Count – number of vehicles/travelers passing 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
65
Definitions
• Congested flow: A traffic flow condition caused by a downstream bottleneck bottleneck. • Over Saturation: A traffic condition in which the arrival flow rate exceeds capacity.
66
33
8/30/2012
Definitions
Traffic Intensity Capacity Demand
Congestion
Volume
Time
67
Traffic Stream Parameters
Average annual daily traffic (AADT). The average 24hour volume at a given location over a full 365-day year. Average daily traffic (ADT) The average 24-hour (ADT). volume at a given location over a defined time period less than one year. Average Weekday Traffic (AWT) Average Annual Weekday Traffic (AAWT)
68
34
8/30/2012
AADT Estimation Trends Method
AADT 1997 1998 1999 2000 2001 2002 2003 2004 Year
69
AADT Estimation
Growth 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 = 70 1,200 · (1 + 0.03)2004-2000 = 1,350 veh/day
35
8/30/2012
“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 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.
72
36
8/30/2012
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.
73
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 flow flow. Factors K & D are based upon local or regional characteristics at existing locations.
74
37
8/30/2012
30th Highest Hourly Volume
• It is uneconomical to attach too much importance to the exceptionally high peaks of traffic volume which occur on only a few occasions throughout the year. • So particularly we never design a carriage way to be So, congestion 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 the volume for which the ratio of benefit and expenditure (cost) is near the maximum. • Roads are designed to carry this volume.
75
Traffic Stream Parameters
Peak Hour Factor (PHF) The relationship between hourly volume and the maximum rate 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 (dense urban areas). Can be used to estimate a max flow rate within an hr based on the full hr-volume. Max rate of flow within the hr, v=V (hourly vol) / PHF (v & V in veh / h)
76
38
8/30/2012
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
77
PEAK HOUR AND PEAK HOUR FACTOR-EXAMPLE
Time Flow/5 Min 9:00 9:05 100 9:05 9:10 80 9:10 9:15 90 9:15 9:20 100 9:20 9:25 100 9:25 9:30 100 9:30 9:35 100 9:35 9:40 200 9:40 9:45 244 9:45 9:50 250 9:50 9:55 220 9:55 10:00 200 10:00 10:05 100 10:05 10:10 100 10:10 10:15 100 10:15 10:20 100 10:20 10 25 10 20 10:25 90 10:25 10:30 87 10:30 10:35 85 10:35 10:40 85 10:40 10:45 83 10:45 10:50 80 10:50 10:55 78 10:55 11:00 69
PHF
300
250
Veh Count
200
150
100
50
0
Time
78
39
8/30/2012
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 = 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 ( p g (variation) within one hour. )
79
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 • 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.
80
40
Traffic Engg and Safety CE-444
1
TRAFFIC ENGINEERING & SAFETY
Credit Hours 2 + 1 = 3 (16 weeks) Total P i d (32 48) T t l Periods : (32+48) = 80
Text Book
1. Priciples of Highway Engineering and Traffic p f g y g g ff Analysis by Fred L. Mannering, W.P.Kilareski, and S.S.Washburn 2. “Introduction to Traffic Engineering, a manual for data Collection and analysis” by Thomas R Currin. 2
1
8/30/2012
Course Outline
Introduction
• • • • •
(4)
Typical Transportation/Traffic Issues and Solutions Introduction to Traditional Traffic Studies Modes of Transport Traffic Engineering Elements Traffic Surveys
3
Course Outline
Traffic Flow Characteristics
(1) ( ) (2) (3) (3) (4) (5) (6) (7)
(10)
Nature of Traffic Flow Parameters Connected With Traffic Flow Interrupted and Uninterrupted Traffic Analysis of Speed Flow and Density Relationship Traffic Stream Characteristics and Models: Flow, Speed, Density Queuing Theory, Queuing Models and Analysis Traffic Volume Studies Highway Level of Service Analysis
4
2
8/30/2012
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
5
Course Outline
Traffic Safety
•
(08)
• • • • • •
Introduction y Traffic Safety Measures Basics of Highway Safety management Highway Safety Analysis Traffic Safety Audits and Identification Of Hazardous Location Safety Considerations in Highway Design Highway Safety Countermeasures
6
3
8/30/2012
Course Outline
Practicals
• • • • • • • • • •
(48)
Spot speed study Turning movement counts / vehicle counts g 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”
7
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 interest p within the scope of this course. Students are required to submit a project report and present their projects at the end of the course. The term project may include any case study or identification of a real time traffic or safety problem and recommended solution. Due importance is given to learning the procedure to carryout research and case reporting (preparation of a project report).
8
4
8/30/2012
Grade Distribution
Total 100
34% 66%
5% of Sessional 10% of Sessional 35% of Sessional 50% of Sessional
50-60% of Practical 40–50% of Practical
Fi l E Final Exam Sessional Assignment Quiz Class Test Practical
Term Project Lab Work/Field Exercises -
9
Thought of the Day
• Always try your best and be contented on whatever comes to you, because it is the will of Allah. • Always believe that whatever is happening to you in this life is the best from HIM. • It is only HE who knows the BEST and HE knows ALL.
10
5
8/30/2012
Points for Consideration
• Be attentive • Do not hesitate to ask questions • Make notes of what is being taught in the class • Always bring calculators • Always bring the book/notes • Follow the rules/instructions • Always try to be positive 11
Present Transportation Issues and Trends
• 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 Security Congestion management Safety management Multimodalism Intelligent Transportation Systems
• Where are the solutions?
12
6
8/30/2012
Present Transportation Issues and Trends
• 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 Security management Congestion management Safety management Multimodalism Intelligent Transportation Systems
• Where are the solutions?
13
Traffic and safety studies needed for effective congestion and safety management:
Traffic generation, Parking demand, Capacity and quality of traffic, Control and geometry improvements, Road hazard and countermeasures identification dh d d id ifi i
14
7
8/30/2012
What Answers Are Sought?
• • • • • • • • Current highway and parking use Current traffic characteristics Current traffic and parking quality Current highway safety How to improve current traffic conditions p g y projects/improvements p Impact of new highway p j Impact of a new land development Future traffic conditions
15
Scale of the Studies
• Single facilities (intersection, road section) • Arterial streets • Corridors (several parallel roads) • L l areas (part of the network) Local ( t f th t k) • Entire systems (city, province,district)
16
8
8/30/2012
Traditional Traffic Studies
• • • • • • • Volume studies Speed studies Travel time studies Delay studies y Density studies Headway and spacing studies Accident studies
17
Special Traffic Studies and Analyses
• Traffic impact studies and analyses • Safety analyses
– Identification of hazardous locations – Identification of hazard sources – Identification of countermeasures
• • • • •
Corridor studies g Parking studies Congestion analyses Pedestrian studies Before-and-after studies
18
9
8/30/2012
Transportation System
• A transportation system is an infrastructure that serves to move people and goods efficiently. The transportation system consists of fixed facilities, flow entities, and a control component. • Efficient safe, rapid, comfortable, convenient, econo 19 mical, environmentally compatible.
Transportation System
Major transportation subsystems • Land transportation: highway, rail • Air transportation: domestic, international • Water transportation; coastal, rivers • Pi li Pipelines: oil, gas, water il t
20
10
8/30/2012
Highway Transportation System
• Fixed facilities: roads, bridges, intersections, interchanges, s d b id i t ti i t h ervice stations, etc. • Flow entities: passenger cars, buses, trucks, pedestrians, etc. • Control component: highway administration, local transportation agencies (signs, markings, signals)
21
Traffic Engineering
• 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, and relationships between different modes of transportation
22
11
8/30/2012
Traffic Engineering
Traffic studies are carried out to: 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
23
Traffic Engineering
• Traffic Engineering covers a broad range of engineering application with common focus: the nation’s system of highways 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 of public safety and security. f bli f d i – Basic mobility of all societal functions. – Basic access to the most remote regions.
24
12
8/30/2012
Objectives
• Traffic Engineering – “D l with the S f and Effi i t movement “Deals i h h Safe d Efficient
of people and goods on streets and highways” – Other Objectives
• • • • • Speed Comfort Convenience i Economy Environmental compatibility
25
Objectives
• Safety:
– The principal goal of the traffic engineer remains the provision of a safe system f i h ii f f for highway traffic
• Speed:
– While speed of travel is very much desired, it is limited by transportation technology, human characteristics, characteristics and the needs to provide safety
• Comfort:
– Comfort involves the physical characteristics of vehicles and roadways, and is influenced by our perception 26
13
8/30/2012
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 environment – All produce air and noise pollution in some forms, and all utilize valuable land resources
27
Road Functions
Mobility
Accessibility
28
14
8/30/2012
Mobility and Accessibility
• Mobility
– Abilit to travel to many different destinations Ability t t lt diff t d ti ti – Provided by Freeways, Motorways…..
• Accessibility
– Ability to gain access to a particular site or area – Provided by Local Streets
29
Hierarchical Structure of Road Networks
Rural
Urban
30
15
8/30/2012
Mobility vs. Accessibility
Road Class
Freeways/Motorways Arterials Collectors Local Roads
Road Function
Through movement exclusively Through movement primary and some land access Traffic movement to higher rank roads, access to abutting properties Access to abutting land and local traffic movement
31
Mobility vs. Accessibility
32
16
8/30/2012
Mobility vs. Transportation Mode
33
Mobility vs. Transportation Mode
34
17
8/30/2012
Traffic Engineering
Person and Vehicle Movement 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
35
Components of Traffic System
Road Users Drivers Pedestrians Bicyclists Passengers Vehicles Private Commercial Street and Highways Traffic Control Devices General Environment
36
18
8/30/2012
Modes to Transportation
• Urban People Transportation People-Transportation
– – – – Automobile Taxi/For-Hire Vehicles Bus Transit Rail
37
Modes to Transportation
• Intercity People Transportation People-Transportation
– – – – – Automobile Intercity Bus Railroad Air Water
38
19
8/30/2012
Modes to Transportation
• Urban & Intercity Freight Transportation
– – – – – Long-Haul Trucks Local Trucks Railroads Water Air Freight
39
Elements of Traffic Engineering
• • • • • Traffic Studies Facility Design Traffic Control Traffic Operations Performance E l ti P f Evaluation
40
20
8/30/2012
Elements of Traffic Engineering
• Traffic Studies
–I Involve measuring and quantifying various l i d tif i i aspect of highway traffic. Studies focus on data collection and analysis that is used to characterize traffic, including (but not limited to) traffic volumes and demands, speed and travel time delay accidents origins and time, delay, accidents, destinations, modal use, and other variables (e.g. safety).
41
Elements of Traffic Engineering
• Facility design
– Involves traffic engineers in the functional and geometric design of highways and other traffic facilities. – Traffic engineers are not involved in the structural str ct ral design of high a facilities b t highway but should have some appreciation for structural characteristics of their facilities.
42
21
8/30/2012
Elements of Traffic Engineering
• Traffic Control
– is a central function of traffic engineers and involves the establishment of traffic regulations and their communication to the driver through the use of traffic control devices, such as signs, markings, and signals.
• Traffic Operations ffi O i
– Involves measures that influence overall operation of traffic facilities, such as one-way street system, transit operation, and surveillance 43 and network control systems.
Elements of Traffic Engineering
• Performance Evaluation
– Is a mean by which traffic engineers can rate the operating characteristics of individual sections of f iliti and f iliti as a whole. ti f facilities d facilities h l – Such evaluation relies on measures of performance quality and is often stated in terms of “levels of service.” – Levels of service (LOS) are letter grades, from A to F, describing how well a facility is operation using specified performance criteria criteria. (A –Excellent; F- undesirable). – As part of performance evaluation, the capacity of highway facilities must be determined.
44
22
8/30/2012
Elements of Traffic Engineering
• Traffic Systems Management (TSM):
– involves virtually all aspects of traffic engineering in a focus on optimizing system capacity and operations. – Specific aspects of TSM include highoccupancy vehicle priority systems, car-pooling programs, pricing strategies to manage demand, and similar functions.
45
Elements of Traffic Engineering
• Integration of intelligent transportation system technologies (ITS):
– It refers to the application of modern tele-communication technology to the operation and control of transportation system. – Such systems include but not limited to automated toll-collection systems (E-toll), vehicle-tracking systems, in vehicle GPS and mapping systems, automated enforcement of traffic lights and speed laws, Variable Message Signs, etc.
46
23
8/30/2012
Who Are Traffic Engineers’ Clients?
• Policy makers • Highway administration
– State/Province – District – City
• Citizens groups • Land developers • Business owners
47
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.
48
24
8/30/2012
Challenges for a Traffic Engineer
• Growth management is a major current issue. Where development will cause substantial deterioration in the p quality of traffic service, either such development will be disallowed or the developer will be responsible for general highway and traffic improvements that mitigate these negative impacts. • Such policies are more easily dealt with in good economic times. When the economy is sluggish, the issue will often be a clash between the desire to reduce congestion and the desire to encourage development as a means of increasing the tax base.
49
Traffic Flow Characteristics
Basic Concepts Flow Rate Spacing Headway Speed Density Relationships
50
25
8/30/2012
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 Volume: Fl V l Flow rate generalized . Fl t li d Flow i t in terms of vehicles per f hi l hour is called volume.
51
• Types of Traffic Flows – Interrupted flow: Traffic flow is interrupted by fixed elements signals railway crossings etc It elements, signals, etc. causes delay. – Uninterrupted flow: In which flow remains uninterrupted through out its course, i.e., freeways, motorway. Roadway geomerty and interaction between the vehicles cause major influence on vehicular movements.
52
26
8/30/2012
Spacing
The distance (ft) between successive vehicles in a ( ) traffic stream, as measured from front bumper to front bumper
53
Headway (h)
The time between successive vehicles, as their front , bumpers pass a given point.
54
27
8/30/2012
Speed
Time mean speed (spot speed)
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/predefined distance.
55
Time Mean/Spot Speed
v
dx dt
56
28
8/30/2012
Travel Speed/Space Mean Speed
v
x2 x1 t 2 t1
57
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
58
29
8/30/2012
Microscopic Characteristics
Distance x First Vehicle Trajectory Space H d S Headway s
Time Headway h Spot Speed U d Second Vehicle Trajectory Time t
Traffic Stream Measures
Microscopic
Time headway and spacing .
Define characteristics specific to pair of vehicles in the stream
Macroscopic
Flow, speed (space mean speed) and density. Describe the traffic stream as a whole
60
30
8/30/2012
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 (freeway, multilane, 2-lane rural, signals)
61
Mobility vs. Transportation Mode
Capacity capacity in veh/h = capacity in veh/h/lane x number of lanes capacity in persons/h = capacity in veh/h x average vehicle occupancy
62
31
8/30/2012
Mobility vs. Transportation Mode
Capacity Facility
Three-lane urban freeway Three-lane urban arterial One lane of buses
Vehicles/hr
2,000 x 3 = 6,000 800 x 3 = 2,400 100 x 1 =100
Persons/hr
6,000 x 1.7 = 10,200 2,400 x 1.7 = 4,080 100 x 80 = 8 000 8,000
63
Factors Reduce Capacity of Highway
• Alignment • Commercial Vehicles • Lane Width • Grade • Pedestrians • Weather Conditions • Parked Vehicles
64
32
8/30/2012
Definitions
• Count – number of vehicles/travelers passing 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
65
Definitions
• Congested flow: A traffic flow condition caused by a downstream bottleneck bottleneck. • Over Saturation: A traffic condition in which the arrival flow rate exceeds capacity.
66
33
8/30/2012
Definitions
Traffic Intensity Capacity Demand
Congestion
Volume
Time
67
Traffic Stream Parameters
Average annual daily traffic (AADT). The average 24hour volume at a given location over a full 365-day year. Average daily traffic (ADT) The average 24-hour (ADT). volume at a given location over a defined time period less than one year. Average Weekday Traffic (AWT) Average Annual Weekday Traffic (AAWT)
68
34
8/30/2012
AADT Estimation Trends Method
AADT 1997 1998 1999 2000 2001 2002 2003 2004 Year
69
AADT Estimation
Growth 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 = 70 1,200 · (1 + 0.03)2004-2000 = 1,350 veh/day
35
8/30/2012
“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 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.
72
36
8/30/2012
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.
73
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 flow flow. Factors K & D are based upon local or regional characteristics at existing locations.
74
37
8/30/2012
30th Highest Hourly Volume
• It is uneconomical to attach too much importance to the exceptionally high peaks of traffic volume which occur on only a few occasions throughout the year. • So particularly we never design a carriage way to be So, congestion 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 the volume for which the ratio of benefit and expenditure (cost) is near the maximum. • Roads are designed to carry this volume.
75
Traffic Stream Parameters
Peak Hour Factor (PHF) The relationship between hourly volume and the maximum rate 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 (dense urban areas). Can be used to estimate a max flow rate within an hr based on the full hr-volume. Max rate of flow within the hr, v=V (hourly vol) / PHF (v & V in veh / h)
76
38
8/30/2012
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
77
PEAK HOUR AND PEAK HOUR FACTOR-EXAMPLE
Time Flow/5 Min 9:00 9:05 100 9:05 9:10 80 9:10 9:15 90 9:15 9:20 100 9:20 9:25 100 9:25 9:30 100 9:30 9:35 100 9:35 9:40 200 9:40 9:45 244 9:45 9:50 250 9:50 9:55 220 9:55 10:00 200 10:00 10:05 100 10:05 10:10 100 10:10 10:15 100 10:15 10:20 100 10:20 10 25 10 20 10:25 90 10:25 10:30 87 10:30 10:35 85 10:35 10:40 85 10:40 10:45 83 10:45 10:50 80 10:50 10:55 78 10:55 11:00 69
PHF
300
250
Veh Count
200
150
100
50
0
Time
78
39
8/30/2012
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 = 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 ( p g (variation) within one hour. )
79
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 • 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.
80
40
