Transcript Lecture 7 - جامعة فلسطين

Faculty of Applied Engineering and Urban Planning
Civil Engineering Department
1st Semester 2009/2010
ECGD 4121 – Transportation Engineering I
Lecture 7
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Studies of Traffic Engineering
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Content
• Speed Studies
• Volume Studies
• Travel Time & Delay Studies
• Parking Studies
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Speed Studies
Basic Methods:
• Pneumatic road tube
• Inductive loop detectors
• Video detectors
• Others
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Speed Studies
Speed characteristics expressed using:
• Average speed (arithmetic mean)
• Median speed
• Modal speed
• ith percentile spot speed (85th, 95th)
• Standard deviation
• Basic statistic analyses
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Data Sources
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Data Sources
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Data Sources
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Data Analyses
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Data Analyses
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Data Analyses
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Data Analyses
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Data Analyses
Volume characteristics expressed using:
• Average Annual Daily Traffic (AADT)
• Average Daily Traffic (ADT)
• Peak Hour Volume (PHV)
• Vehicle Miles of Travel (VMT)
• Vehicle Classification (VC)
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Data Analyses
Average Annual Daily Traffic (AADT)
• Vehicles per day (VPD) in both directions
• Expressed as average of 24 hours counts
for 365 days (1 year)
• Used for determining and assigning traffic
trends, feasibility studies, etc
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Data Analyses
Average Daily Traffic (ADT)
• Vehicles per day (VPD) in both directions
• Expressed as average of 24 hours counts for a
number of days less than 1 year
• Used for planning, measurement of current
demand, evaluate traffic flow
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Data Analyses
Peak Hour Factor
Peak Hour Volume
(4)(Volumeduring 15 minuteswithin peak hour)
PHF 
PHV
(4)(PV15 )
Design Hourly Volume  DHV 
PHV
PHF
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Data Analyses
Example: The afternoon peak hour traffic flow
data for westbound traffic on a major road are:
4:45pm-5:00pm
400 vehicles
5:00pm-5:15pm
700 vehicles
5:15pm-5:30pm
600 vehicles
5:30pm-5:45pm
400 vehicles
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Data Analyses
Data Analyses:
• PHV = 400 + 700 + 600 + 400 = 2100 vehicles
• PV15 = 700 vehicles
• PHF = 2100/(4)(700) = 0.75
• DHV = 2100/0.75 = 2800 vehicles
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Traffic Volume Counting
Methods of Counting:
• Manual methods
• Automatic methods
 Surface detectors such as pneumatic road
tubes
 Subsurface detectors such as magnetic or
electric contact devices
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Traffic Volume Counting
Types of Counts:
• Cordon counts
• Screen line counts
• Intersection counts
• Pedestrian volume counts
• Periodic volume counts
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Traffic Volume Counting
Adjustment of periodic counts:
• Using data from continuous counting stations
we can obtain the Hourly Expansion Factors
• HEF = total volume for 24-hr period/volume
for a particular hour
• HEF is used to expand counts of durations
shorter than 24 hr to 24-hr volumes (must use
HEF obtained from similar class of roads)
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Traffic Volume Counting
Adjustment of periodic counts:
• Daily Expansion Factors (DEF) = Average total
volume
for
week/average
volume
for
particular day
• DEF is used to determine weekly volumes
from counts of 24-hr duration (must use DEF
obtained from similar class of roads)
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Traffic Volume Counting
Adjustment of periodic counts:
• Monthly Expansion Factors (MEF) =AADT/ADT
for particular months
• MEF is used to determine AADT from ADT for
a given month (must use DEF obtained from
similar class of roads)
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Travel Time & Delay Studies
Studying the route from “A” to “B” to:
• Determine travel time
• Determine route efficiency
• Identify delay locations
• Evaluate “before & after” performance
• Feasibility studies
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Travel Time & Delay Studies
Travel-time estimation: The moving car method
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Travel Time & Delay Studies
• Requires one testing vehicle, one driver, and
three observers on board.
• Observer #1: counts mean time the testing car
takes to travel eastward and westward.
• Observer #2: counts the number of vehicles
traveling in opposite direction
• Observer #3: counts the number of vehicles
that overtook and are overtaken by the testing
vehicle
• Driver: if possible try to balance the number of
vehicles (overtaking vs. overtook)
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Parking Studies
• The characteristics of the parking facility and
parking behavior
• Parking facility: full time and part time
• Parking behavior: short time and long time –
rate of use of a parking space
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Parking Studies
Definition of Parking Terms:
• Space-hour: the use of a single parking space
during a period of time.
• e.g., one space-hour can be either one vehicle
parked one hour at one parking lot, or two
vehicles parked 30 minutes each at one
parking lot.
• e.g., the maximum capacity of a full time (8:00
AM – 6:00 PM) garage with 200 parking lots is:
(200 vehicles)(10 hours) = 2000 veh.hr.
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