traffic engineering · 2018. 12. 2. · note: (365 day / 7 days a week) = 52.14 52.14 * 5 (weekday)...

Civil Engineering Department TRAFFIC ENGINEERING Third Year 2018

Lecturer: Dr. Mohammed Bally Mahdi 0

TRAFFIC ENGINEERING

Third year 2018

Dr. MOHAMMED BALLY MAHDI

[email protected]

AL-Muthanna University College of Engineering

Civil Engineering



TRAFFIC ENGINEERNG References:

1. Traffic and Highway Engineering, Nicholas J. Garber. Fourth Edition. 2. Traffic Engineering, Roger P. Roess. Fourth Edition. 3. Introduction to Transportation Engineering, Fd.Hobbs. (2002). 4. Traffic Engineering-An Introduction, Gorden R.Wells.

INTRODUCTION TO TRAFFIC ENGINEERING Transportation is the movement of humans and goods from one location to

another. Modes of transport include air, rail, road, water, cable, pipeline and

space. The field can be divided into infrastructure, vehicles and operations.

Transport is important because it enables trade between people, which is essential

for the development of civilizations.

Lectures introduction:

The traffic engineering lectures cover the fundamentals of planning, design, and

operation of traffic movements. We will discuss the various topics including road

vehicles performance, geometric design of highways, traffic flow, highway

capacity analysis and design of intersections.

Purpose of the lectures:

The objective of the traffic engineering lectures for students is to develop a basic

understanding of the principles of highway engineering and traffic analysis. The

students should be able to apply these concepts and principles to analyze various

traffic characteristics and problems.



Definitions of:

1. Transportation Engineering: Is the application of technology and scientific

principles to the planning, design, operation, maintenance and

management of systems and facilities for any mode of surface

transportation in order to provide for the safe, rapid, comfortable,

convenient, economical, and environmentally compatible movement of

people and goods.

ألي والمرافق النظم وإدارة وصیانة وتشغیل وتصمیم لتخطیط العلمیة والمبادئ التكنولوجیا تطبیق ھو

للناس بیئیا ومتوافقة واقتصادیة، ومریحة وسریعة آمنة حركة توفیر أجل من البري النقل یلةوس

.والبضائع

2. Traffic Engineering: Is that phase of transportation engineering that deals

with the safe and efficient planning, geometric design and traffic

operations of roads, streets and highways, their networks, terminals,

abutting lands and relationships with other motorized and non-motorized

modes of transportation.

وعملیات الھندسي والتصمیم والفعال اآلمن التخطیط مع تتعامل التي النقل ھندسة من المرحلة تلك ھي

المتاخمة األراضي یخص فیما والمحطات، وشبكاتھا، السریعة، والطرق والشوارع الطرق من المرور

.األخرى اآللیة وغیر اآللیة النقل وسائط انواع مع والعالقات

Traffic System Components

Five critical components interact in a traffic system:

1. Road users: مستخدمي الطریق (drivers, pedestrian, bicyclists and passengers)

2. Vehicles: المركبات (private and commercial)

3. Streets and highways. السریعة والطرق الشوارع

4. Traffic control devices. المرور حركة سیطرة أجھزة

5. The general environment. العامة البیئة

General objectives:



The definitions of transportation and traffic engineering high-light the following

objectives:

1. Safety. السالمة

2. Speed. السرعة

3. Comfort. الراحة

4. Convenience. المالثمة

5. Economy. االقتصادي

6. Environmental compatibility. التوافق البیئي

Elements of Traffic Engineering

1. Traffic studies and characteristics.

2. Performance evaluation.

3. Facility design.

4. Traffic control.

5. Traffic operations.

6. Transportation systems management.

7. Integration of intelligent transportation system (ITS) technologies.



Highway Classification:

A) Physical Classification. (Geometric design)

B) Functional Classification. (Service)

A) Physical Classification

1. 2-lane highway: having two lanes cross section with one lane on each direction.

Typical Cross Section for Two-Lane Highways

2. Multilane highway: a highway with two lanes at least in each direction

and it may be divided by physical median or undivided (signs).

Typical Cross Section for Multilane Highways (half section)



B) Functional Classification.

Highways are classified according to their functions in terms of the service they

provide into:

1- Principal arterials: This system of highways serves the major activity

centers of the urban area and consists mainly of the highest-traffic-volume

corridors. (Design speed ≥ 120 km/h)

2- Minor Arterial System: Streets and highways that interconnect with the

urban primary arterials are classified as urban minor arterials. (Design speed

100 km/h).

3- Collector Street System: The main purpose of streets within this system is to

collect traffic from local streets in residential areas or in CBDs and convey it to

the arterial system (Design speed =80 km/h).

4- Local Street System: The primary purposes of these streets are to provide

access to abutting land and to the collector streets (Design speed = 20-40 km/h)



Traffic studies and characteristics

A. Traffic studies: Traffic Stream Parameters: 1) Volume 2) ADT 3) AADT 4) Rate of flow 5) Capacity 6) PHF 7) Speed and Travel time 8) Density and Occupancy 9) Spacing and Headway B. Characteristics: 1) Driver 2) Pedestrian 3) Vehicle 4) Road

TRAFFIC STREAM PARAMETERS

1) Volume:

It is the number of vehicles passing a given point during a specified period of time, or the number of vehicles that pass over a given section of a lane or a roadway during a specified period of time.



Traffic volume studies

Traffic volume studies are conducted to collect data on the number of vehicles and/or pedestrians that pass a point on a highway facility during a specified time period. Traffic volume studies are usually conducted when certain volume characteristics are needed and traffic volume can be expressed in terms of:-

1) Average daily traffic (ADT): معدل المرور الیومي

Is the average of 24-hour counts collected over a number of days greater than one but less than a year. commonly abbreviated as ADT. ADTs may be used for:

a) Planning of highway activities. b) Measurement of the current demand. c) Evaluation of existing traffic flow.

تلك الفترة معدل المرور الیومي: یحسب بقسمة عدد المركبات في فترة معینة على عدد األیام في

Note: Daily volume are given for entire road way (both directions), otherwise specified. For example: 10000 vpd in both directions.

2) Average annual daily traffic (AADT): معدل المرور الیومي السنوي

Is the average of 24-hour counts collected every day of the year. AADTs are used in several traffic and transportation analyses for: a. Estimation of highway user revenues b. Computation of crash rates in terms of number of crashes per 100 million vehicle miles. c. Establishment of traffic volume trends. d. Evaluation of the economic feasibility of highway projects. e. Development of freeway and major arterial street systems. f. Development of improvement and maintenance programs.

ADT = ( )

AADT =



3) Average weekday traffic (AWT): معدل المرور األسبوعي

4) Average annual weekday traffic (AAWT): معدل المرور األسبوعي السنوي

Note: (365 day / 7 days a week) = 52.14

52.14 * 5 (weekday) = 260

Average annual daily traffic (AADT)

Aver

age

annu

al d

aily

traf

fic (A

ADT)

AAWT =

AWT =



Average daily traffic (ADT)



1) Rate of flow (flow Rate) q:

The equivalent hourly rate at which vehicles pass over a given point or

section of a lane or roadway during a given time interval of less than 1h,

usually 15 min.

Peak flow rates and hourly volumes produce the peak-hour factor (PHF).

2) Peak hour factor (PHF):

The ratio of total hourly volume to the peak flow rate (the maximum

rate of flow) within the hour, computed by the following Equation:

In practical terms, the PHF generally varies between a low of 0.7 for

rural and developed areas to 0.98 in dense urban areas.

For standard 15 minute analysis period, this becomes:

Where:

PHF = Peak hour factor

V= Hourly volume, (veh)

V max 15 = Maximum 15 minute volume within the hour, veh

Example:

q = Maximum rate of flow x number of intervals per 1 hour

= ( ) ( )

=∗



3) Capacity:

It represents the maximum number of vehicles that can pass a given point

during a period of time under prevailing condition, commonly expressed

as (pcuphpl).

Example: traffic volume data has been collected for 15 min time intervals as shown below. Find the average spacing for this traffic flow with average speed as 80 km/h. Time 7:30 – 7:45 7:45 – 8:00 8:00 – 8:15 8:15 – 8:30 Volume 250 350 300 200 Solution: Volume = 250+350+300+200 = 1100 veh Flow rate (q) = peak volume * number of intervals per 1 hour = 350 * 4 = 1400 veh/hr Density = q/s

= 1400/ 80 = 17.5 veh/km

Spacing = 1000/17.5 = 57.14 m

=∗

= 0.875



4) Speed and Travel time:

Speed : Is defined as a rate of motion in distance per unit time.

Travel time: Is the time taken to traverse a defined section of roadway. Speed and

travel time are inversely related:

Where: S = Speed , km/h or m/s d = Distance traversed. km or m t = Time to traverse distance d , h or s

5) Density (D):

Is defined as the number of vehicles traveling over a unit length of highway at an

instant in time, generally expressed as vehicles per kilometer or vehicles per

kilometer per lane.

From the definition of

the density:

Direct measurement of density in the field is difficult; therefore, density can be

computed from the average travel speed and flow rate using the following

relationship:

Where: D = Density , veh/km or veh/km/ln q = Rate of flow (traffic flow), veh/h or veh/h/ln S = Average speed, km/h

S =

(ℎ) =

. ℎ ℎ ℎ ( )

D(veh/km) =



Relationships among Speed, Flow and Density

6) Spacing and Headway

Spacing: The distance (in meters) between successive vehicles in a traffic stream,

as measured from front bumper to front bumper.

Headway: The time (in

seconds) between successive vehicles, as their front bumpers pass a given point.

The average headway in a lane is directly related to the rate of flow:

Where: q = Rate of flow (traffic flow), veh/h or veh/h/ln ha = Average headway in the lane, s

n

iia hn

h1

1

ahq 3600

traffic engineering · 2018. 12. 2. · note: (365 day / 7 days a week) = 52.14 52.14 * 5 (weekday)...

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