2. General objective (Blue Print)
• Traffic Engineering studies:
– spot speed studies,
– volume studies,
– travel time and delay studies
– parking studies and road traffic safety.
• Fundamental principles of traffic flow:
– traffic flow elements, and
– flow-density relationships.
3. General objective (Blue Print)
• Highway capacity:
– level of service,
– capacity of highways,
– and intersections
• Traffic control devices and systems:
– traffic signs,
– pavement markings and islands,
– and traffic signals.
4. 1) One of the major contributions using the fluid-flow analogy for describing traffic streams
in quantitate terms was developed by
a) Greenshields
b) Greenberg
c) Underwood
d) Under shields
2) An expert who hypothesized that there is a linear relationship existed between speed and
density of traffic stream
a) Greenshields
b) Greenberg
c) Underwood
d) Under shields
3) One of the following is not fundamental characteristics of traffic flow
a) traffic doesn’t flow at a uniform rate through the hours, day, season and year
b) the position of each vehicle in a traffic stream is independently controlled
c) the characteristics of a traffic stream depend on its composition
d) traffic flow is a stochastic process
e) None of the above
Sample Questions
5. 1) The harmonic mean of the speeds of vehicles passing a point on a highway during an
interval of time
a) Time mean speed
b) Space mean speed
c) Time headway
d) Space headway
e) None of the above
2) Which one of the following is used as a measure of effectiveness in defining level of service
of multilane highways?
a) Speed
b) Flow
c) Density
d) Travel time
e) All of the above
3) In the capacity analysis of a facility the assumed terrain type as a base condition is:
a) Mountainous
b) Rolling
c) Flat
d) Escarpment
Sample Questions
6. 1) Which one is correct in the analysis of LoS of Two-lane highway segment
a) Free flow speed (FFS) > average travel speed (ATS) > Base free flow speed (BFFS)
b) BFFS > FFS >ATS
c) ATS >FFS >BFFS
d) ATS > BFFS > FFS
e) None of the above
2) How many level of service types can be defined to characterize operational conditions of
any transportation facility within a traffic stream
a) 5
b) 4
c) 3
d) 6
e) 2
3) In the capacity analysis of a facility the assumed vehicle type as a base condition is:
a) Bus
b) Truck
c) Recreational vehicle
d) Small car
e) None of the above
Sample Questions
7. 1) Which one is correct about Capacity of any facility
a) It is independent of the directional distribution of traffic
b) It is conducted for a facility having uniform traffic, roadway, and control conditions
c) Actual volume is frequently higher than capacity when congestion exists
d) The capacity of trunk roads in Ethiopia is the same from location to location.
e) None of the above
2) The Greenberg model is used for which type of traffic condition?
a) Dense
b) Light
c) Uncongested
d) Unrestricted
3) a and bWhich of the following is a model that is commonly used by the macroscopic
approach?
a) Macroscopic Simulation Models
b) Mesoscopic Simulation Models
c) Greenshields model
d) Travel Demand Models
e) All of the above
Sample Questions
8. Traffic flow elements
• Traffic stream parameters fall into two broad categories:
– Macroscopic parameters
• describe the traffic stream as a whole
• The three principal Macroscopic parameters are:
– Volume or Rate of flow
– Speed
– density
– Microscopic parameters
• describe the behavior of individual vehicles or pairs of vehicleswith
in the traffic stream
• It includes:
– The speed of individual vehicles
– headway
• Two principal categories of traffic facilities:
– Uninterrupted flow
– Interrupted flow
– Spacing
13. Mathematical Relationships(macroscopic
models) Describing Traffic Flow
• Greenshields Model
– Greenshields carried out one of the earliest recorded
works in which he studied the relationship between
speed and density.
– He hypothesized that a linear relationship existed
between speed and density which he expressed as
16. Mathematical Relationships(macroscopic
models) Describing Traffic Flow
• Greenberg Model.
– Several researchers have used the analogy of fluid
flow to develop macroscopic relationships for
traffic flow.
– One of the major contributions using the fluid-flow
analogy was developed by Greenberg in the form
17.
18.
19. Model Application
• Use of these macroscopic models depends on whether they
satisfy the boundary criteria of the fundamental diagram of
traffic flow at the region that describes the traffic conditions.
• For example, the Greenshields model satisfies the boundary
conditions when the density k is approaching zero as well as
when the density is approaching the jam density kj.
• The Greenshields model therefore can be used for light or dense
traffic.
• The Greenberg model, on the other hand, satisfies the boundary
conditions when the density is approaching the jam density, but it
does not satisfy the boundary conditions when k is approaching
zero.
• The Greenberg model is therefore useful only for dense traffic
conditions
20. Dynamic traffic studies
• involve the collection of data under
operational conditions and
• include studies of:
– speed,
– traffic volume,
– travel time and delay,
– parking, and
– crashes.
21. Sample Questions
1)Traffic volume expressed in terms of Passenger Car Unit (PCU) may
be used for except :
a) Capacity analysis
b) Level of Service analysis
c) Structural design of a road
d) Intersection design of a road
e) None of the above
1) Spot speed studies are conducted to ______
a) estimate distribution of speeds of vehicles in traffic at a particular
location
b)estimate distribution of traffic density at a particular location
c) survey various locations based on speed
d)survey various locations based on traffic density
e) All of the above
22. TrafficVolume Study is defined as the survey of number of vehicles
and pedestrians crossing
section of road per unit during any selected period.
Purpose TrafficVolume Study
Establish relative importance of any road.
Structural design ofroads.
Planning and design of new streets.
Design of intersections and other control devices
Planning, design and regulation of traffic.
Establish properties and schedules for traffic improvements.
Traffic volume study is carried out for vehicles and pedestrians
separately or might be combined.
It is carried out at number of selected positions along the road called
as traffic count stations. 2
2
23. It is usually expressed
in terms of Passenger
Car Unit (PCU) and
measured to calculate
Level of Service of the
road and related
attributes like
congestion, carrying
capacity, V/C Ratio,
identification of peak
hour or extended
peak hour etc.
• It is a vehicle unit used for
expressing highway
capacity.
• One car is considered as a
single unit, cycle,
motorcycle is considered as
half car unit.
• Bus, truck causes a lot of
inconvenience because of its
large size and is considered
equivalent to 3 cars or 3 PCU.
2
3
24. TrafficVolume Count can be done by various
methods depending upon various factors like
manpower available, budget,
technology/instrument available,
magnitude of traffic data required or to be
collected which will then determine quality and
type of vehicle classification to be adopted.
Traffic counting falls in two main categories, namely:
manual count and
automatic count.
2
4
25. In order to predict traffic flow volumes that can be expected
on the road network during specific periods, knowledge
of the fact is required that traffic volumes changes
considerably at each point in time.
There are three important cyclical variations:
Hourly pattern: the way traffic flow characteristic varies throughout
the day and night;
Daily Pattern:The day-to-day variation throughout the week
Monthly and yearly Pattern:The season-to-season variation
throughout the year.
5
5
26. VOLUMECHARACTERISTICS
2
6
Traffic volumestudies are usuallyconducted when
certain volume characteristics are needed, some
ofwhichfollow:
Average Annual Daily Traffic (AADT)
the averageofthe 24-hr counts collectedeverydayin the year.
used in severaltraffic and transportation analysis.
computation ofaccident rate
developmentofimprovement and maintenance program
evaluationofthe economicfeasibilityofhighway projects
27. VOLUMECHARACTERISTICS
2
7
Average Daily Traffic (ADT)
the average of 24-hr counts collected over a number of days greater than 1but
less than a year.
ADTsmaybe used for
planningofhighway activities
measurment of current demand
evalution of existing trafficflow
Peak Hour Volume (PHV)
the maximum number ofvehiclesthat pass a point on a highwayduring a period of
60 consecutiveminutes.
PHVsare used for
functional classificationof highways
design ofthe geometric characteristics ofahighway,for example,number of
lanes,intersection signalization and channelization
capacity analysis
development ofparkingregulations
28. VOLUMECHARACTERISTICS
2
8
Vehicle Classification (VC)
records volumewith respect ofthe type ofvehicles,for example,
passenger cars, trucks etc....
VCisusedin
designofgeometric characteristics (turning radii,grade, lane)
capacityanalysis,with respect to passenger car equivalentsof truck
structural design ofhighwaypavement,bridges and soforth
Vehicle Miles ofTravel (VMT)
a measure oftravel alonga section ofroad.
it is the product ofthe traffic volume(that is,averageweekday
volumeorADT)and the length ofroadwayin milesto whichthe
volumeisapplicable.
29. Speed characteristics determined from spot speed study may
be used to:
establish parameters for traffic operation and control, such as
speed zones, speed limits (85th percentile speed is commonly
used as the speed limit on aroad), and passing restrictions.
evaluate the effectiveness of traffic control devices, such as
variable messagesigns at work zone.
monitor the effectofspeed enforcementprogram
evaluateand or determine the adequacyofhighwaygeometric
characteristics such as radii of horizontal curve and length
of vertical curve.
evaluatethe effectofspeed on highway safety
determine speedtrends 2
9
30. Locations for Spot Speed Studies
Represent different traffic conditions on a
highway for basic data collection.
Mid-blocks of urban highways and straight,
level sections of rural highways for speedtrend
analyses.
Any location may be used for solution
of a specific traffic engineering
problem.
3
0
31. Locations for Spot Speed Studies Should be
selected to achieve the following:
Unbiased data
Drivers be unaware
Equipment concealedfrom the driver,
Observers inconspicuous.
3
1
32. Time of Day and Duration of Spot
Speed Studies
depends on the purpose of the
study.
recommended when traffic is free-
flowing,
during off-peakhours.
typically:
the duration is at least 1 hour and
the sample size is at least 30
vehicles.
3
2
33. Median speed
speed at the middle valuein a series ofspot speeds
Modal speed
speed valuethat occurs most frequantly
The ith-percentile spot speed
spot speed value below which i-percent of the vehicles travel;
for example, 85th- percentile spot speed is the speed below
which 85 percent of the vehicles travel and above which 15
percent ofthe vehicles travel
Pace
the range ofspeed – usuallytaken as 10
Standard deviationof speeds
measure ofthe spread ofthe individual speeds. 7
0
35. Introduction
• One of the most critical needs in traffic engineering is a
clear understanding of how much traffic a given facility
can accommodate and under what operating conditions.
• These important issues are addressed in highway
capacity and level-of-service analysis.
• Capacity analysis involves:
– the quantitative evaluation of the capability of a road section
to carry traffic,
– and it uses a set of procedures to determine the maximum
flow of traffic that a given section of highway will carry
under prevailing roadway, traffic and control conditions.
36. Cont’d
• The base conditions include:
– lane widths greater than or equal to 3.6 m,
– clear shoulders wider than or equal to 1.8 m,
– no no-passing zones on the highway,
– all passenger cars in the traffic stream,
– no impediments to through traffic due to traffic
control or turning vehicles, and
– level terrain.
– 50/50 directional split of traffic
37.
38. The Level-Of-Service Concept
• Six levels of service
are defined for each
type of facility for
which analysis
procedures are
available
• Levels-of –Service are
basically step-
functions, each
representing a range
of operating
conditions.
39.
40. Procedures for determining LOS on
two-lane highways
General Procedures
• Input
- Geometric data
- Demand volume
- Field measured speed (SFM)
or base free-flow speed (BFFS)
• Compute free-flow speed
• Compute flow rates
• Compute average travel speed
• Compute percent time spent
following
• Determine level of service
Adjustment factors
• Base free-flow speed adjustment
- Lane width
- Shoulder width
- Access point density
• Field measured speed adjustment
- Volume
- Heavy vehicle
• Volume adjustment for average
speed
- Peak-hour factor
- Heavy vehicle
- Grade
41.
42. FACTORS AFFECTING CAPACITY
AND LEVEL OF SERVICE
• BASE CONDITIONS
– Base conditions assume good weather, good pavement conditions, users
familiar with the facility, and no incidents impeding traffic flow.
– Examples
• lane widths of 3.6 m and level terrain
• only passenger cars in the traffic stream (no heavy vehicles)
• no pedestrians
In most capacity analyses, prevailing conditions differ from the base conditions so, need
adjustment factor.
• ROADWAY CONDITIONS
• TRAFFIC CONDITIONS
– vehicle type
– lane distribution and directional distribution.
• CONTROL CONDITIONS
– traffic signal.
– Stop signs and yield signs
• TECHNOLOGY
57. Sample questions
1. Component of road furniture which identify streets for the unfamiliar,
especially benefiting visitors, postal workers and the emergency services.
a. Benches
b. Traffic barriers
c. Traffic lights
d. Traffic signs
e. None of the above
2. A manual which explains about the principal standard governing the
application, design, and placement of TCD (Traffic Control Device)
a. ERA manual
b. AACRA manual
c. AASHTO manual
d. MUTCD manual
e. All of the above
3. Which one of the following cannot be considered as the components of
road furniture
a. Benches
b. Traffic barriers
c. Traffic lights
d. Traffic signs
e. None of the above
58. 4. The most easily visible characteristic of a traffic control device
a. Shape
b. Colors
c. Pattern
d. Legend
e. All of the above
5. For which of the following locations you may not recommend installation of
delineators
a. locations where the alignment might be confusing or unexpected
b. at lane reduction transitions and curves
c. on long continuous sections of highway
d. through short stretches where there are changes in horizontal alignment
e. None of the above
6. The two most important mandatory traffic signs are
a. speed limit signs and alignment signs
b. warning signs and regulatory signs
c. Stop sign and yield sign
d. Guidance sign and informatory signs
e. All of the above
7. Which one of the following is the most efficient traffic signal system.
a. simultaneous system
b. alternate system
c. simple progressive system
d. flexible progressive system
e. All of the above
59. Introduction
• Street furniture also called road furniture
– is a collective term for objects and pieces of
equipment installed along streets and roads for
various purposes.
• It includes benches, traffic barriers, bollards,
post boxes, phone boxes, streetlamps, traffic
lights, traffic signs, bus stops, tram stops, taxi
stands, public lavatories, fountains, watering
troughs, memorials, public sculptures, and
waste receptacles.
61. Cont.…
• The design and placement of furniture should
take into account
– aesthetics,
– visual identity,
– function,
– pedestrian mobility
– and road safety.
62. Introduction to Traffic Control
Devices
• Traffic control devices are the media by which
traffic engineers communicate with drivers.
• The three broad categories of TCDs are:-
– Traffic Marking
– Traffic Signs
– Traffic Signals
• MUTCDThe principal standard governing the
application, design, and placement of TCD
• One of the principal objectives of MUTCD is to
establish uniformity in the use, placement, and
design of TCDs.
63. Introduction to Traffic Control
Devices
• The MUTCD addresses three critical aspects
of TCDs.
– Detailed standards for the physical design of the
device (shape, size, colors, legend types & sizes…)
– Detailed standards and guidelines on where
devices should be located
– Warrants or conditions that justify the use of
particular device
64. Introduction to Traffic Control
Devices
• Colors:
– The most easily visible characteristic of a device
– The principal colors are red, yellow, green, orange, black, blue, and
brown/white.
• Shape:
– The next element to be discerned by the driver
• Pattern:
– Used in traffic marking (double solid, solid, dashed, and broken
lines
• Legend:
– The last element of a device
– Must be simple and short do not divert driver’s attention
– Signals and markings convey info through use of color, shape and
pattern, however signs use specific legend.
E.g.. Stop sign shape(octagon), color(red), legend (stop)
65. 1. Road marking
• They fall into three broad categories:
– Longitudinal Markings
– Transverse Markings
– Object Markers and Delineators
• Longitudinal and transverse markings are
applied to the roadway surface using a variety
of materials, the most common of which are
Paint and thermoplastic (a naturally reflective
material).
66. 1.1 Longitudinal Markings
• Broken lines are permissive in character and allows
crossing with discretion,
• Solid lines are restrictive in character and does not
allow crossing except for entry or exit from a side
road or premises or to avoid a stationary obstruction
• Double solid lines indicate severity in restrictions
and should not be crossed except in case of
emergency.
• Types of longitudinal markings: centre line, traffic
lanes, no passing zone, warning lines, border or edge
lines, bus lane markings, cycle lane markings.
67. 1. 2. Transverse Marking
• It is a marking with a component that cuts across a portion
or all of the traveled way.
• When used, all transverse markings are white.
• Transverse markings include
– shoulder markings,
– word and symbol markings,
– stop lines,
– yield lines,
– crosswalk lines,
– speed measurement markings,
– speed hump markings,
– parking space markings (contain transverse & longitudinal)
68. 68
Transverse Markings…
• Pedestrian crossings are provided at places where vehicular
and pedestrian traffic conflict is severe.
•At intersections, the
pedestrian crossings
should be preceded by a
stop line at a distance of
2 to 3m for un-signalized
intersections and at a
distance of 1 metre for
signalized intersections.
69. 1.3 Object Markers and Delineators
• Delineators are particularly beneficial
– at locations where the alignment might be confusing
or unexpected, such as at lane reduction transitions
and curves.
– at night and during adverse weather.
– on long continuous sections of highway or
– through short stretches where there are changes in
horizontal alignment
• Delineators are considered guidance devices
rather than warning devices.
70. 2. Traffic Sign
• The functions of signs are to provide
– Regulations give notice of traffic laws or regulations.
a. prohibitory signs
b. mandatory signs
– Warnings give notice of a situation that might not be
readily apparent.
– guidance for road users show route designations,
destinations, directions, distances, services, points of
interest, and other geographical, recreational, or cultural
information.
• Both words and symbols are used to convey the
messages.
• Signs are not typically used to confirm rules of the
road.
71. 2.1 Traffic signs (warning signs)
• The colour convention of signs is that the legend
will be black in colour with a white background.
The shape used is upward triangular or diamond
with red borders
Right hand curve sign, sign for narrow road, sign
indicating railway track ahead.
72. 2.2 Traffic signs (regulatory
signs)
• prohibitory signs
– are part of regulatory signs
– are intended to inform the highway users of traffic
laws or regulations.
– give definite negative instructions prohibiting the
motorist from making particular manoeuvres.
– they are usually circular with black and white
color.
74. 2.2 Traffic signs (regulatory signs)
• mandatory signs
– are part of regulatory signs
– are intended to convey definite positive
instructions when it is desired that motorists takes
some positive action.
– the two most important mandatory signs are
• stop signs
• yield or give way signs
78. 3. Traffic signals
• term definitions
– cycle:- the period of time required for one complete
sequence of signal indications.
– phase:- a part of the signal cycle allocated at a traffic
movement or a combination of traffic movements.
– interval:- any of the division of the signal cycle during
which signal indications do not change.
– the engineer has to design the signal with the sequence and
duration on individual phases to serve all approaching
traffic at a desired level of service.
– the level of service is measured by the vehicle delay.
– the queue length:- the number of vehicle backed up and the
probability of a vehicle entering the intersection during the
first green phase after arrival.
79. 3. Traffic signals
• types of traffic signals
– the signals are classified into the following types:
i. traffic control signals
a. fixed – time signals
b. manual operated signals
c. traffic actuated (automatic) signals
ii. pedestrian signals
iii. special traffic signals
80. 3. Traffic signals
• types of traffic signal system
– there are four general types of co-ordination of
signals for road network
• simultaneous system
• alternate system
• simple progressive system
• flexible progressive system
81. Signal Timing Design
• It involves finding the appropriate duration for all of
the various signal indications.
• The basic timing elements within each phase include
– green interval
– effective green time
– yellow or amber interval
– all-red interval, the
– intergreen interval
– pedestrian WALK interval, and
– pedestrian crossing interval.
82. Signal Timing Design
• The green interval:
– the period of the phase during which the green signal is
illuminated.
• The yellow or amber interval:
– the portion of the phase during which the yellow light is
illuminated.
• The effective green time:
– contained within the green interval and the amber interval.
• The effective green time, for a phase:
– the time during which vehicles are actually discharging through
the intersection.
• The all-red interval:
– the period following the yellow interval in which all of the
intersection's signals are red.
83. Signal Timing Design
• Intergreen interval:
– the interval between the end of green for one phase and
the beginning of green for another phase.
– the sum of the yellow and all-red intervals.
• Pedestrian WALK interval:
– the portion of time during which the pedestrian signal
says WALK.
• Pedestrian crossing time:
– the time required for a pedestrian to cross the
intersection. .
84. Signal Timing Design
• Pre-Design Data Collection:
– Know roadway conditions surrounding the
intersection.
• This includes the number of lanes, the width of the lanes,
the width of the intersection, the width of the shoulders,
and more.
– collect information regarding the composition of the
traffic, such as the percentage of busses and the
percentage of trucks within the traffic stream.
• know the peak hour volumes and peak fifteen-minute
volumes for all of the various movements.
85. Signal Timing Design
• The Design Process (Webster's method ):
1. Decide on a phasing plan.
2. Calculate the length of the intergreen period for each phase of your
cycle.
3. Calculate the minimum green time for each phase based on the
pedestrian crossing time.
4. Calculate or measure the saturation flow rate for each approach or
lane.
5. Calculate the design flow rate for each approach or lane using the
peak hour volume and peak hour factor.
6. Find the critical movements or lanes, and calculate the critical flow
ratios.
7. Calculate the optimum cycle length.
8. Allocate the available green time using the critical flow ratios from
step six.
9. Calculate the capacity of the intersection approaches or lanes.
10. Check the capacities/design flow rates and green intervals/minimum
green intervals. Adjust your cycle timing scheme if necessary.
86. • The total time required for the pedestrian
movements (T) is the sum of the WALK
allowance (Z) and the time required for a
person to traverse the crosswalk (R).
– R = (width of intersection) / (pedestrian Walking
speeds )
– T = Z + R
