Transcript Data Management & Diagnosis

CE 341 Transportation Planning
Data Management & Diagnosis
Transport Planning Database
Foundation of effective Transportation Planning
Objectives of Collecting data
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Determine existing conditions
Calibration and application of travel forecast models
Evaluation of overall performance of systems operation
Gauging the degree to which planning goals and
objectives are achieved
Two major types:
- Quantifiable data used in technical analysis
- Subjective information (political/decision making
process)
Traffic Study Data
Traffic studies consist of 3 primary
activities:
1. Data Collection: Observing, gathering
and recording data.
2. Data Reduction: Coding, data entry, and
tabulation.
3. Data Analysis: Processing of data to
understand the observed situation,
diagnosis, and plan improvements.
Types of Traffic Data
1.
2.
3.
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Traffic data could be grouped into 4 broad categories:
Physical inventories: Street and highway
inventories, control devices, parking spaces, roadway
conditions.
Population characteristics: Describe various
aspects of road users, their vehicles, route, and travel
behavior.
Operational parameters: The measures that quantify
the characteristics of traffic streams in motion:
volume studies
- Speed studies
Travel time studies
- Delay studies
4. Special Purpose data:
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Accident data
Pedestrian studies
- Parking studies
- Goods movement &transit studies
Sampling Method in Data Collection
It is infeasible - practically and economically- to
develop a database consisting of every single
element of Target population.
Steps in planning and executing survey:
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Establish survey objectives
Define target population
Identify the specific relevant data to collect
Specify the degree of precision required
Determine method to be used in obtaining survey results
Select the sampling procedures and sample size
Pretest the survey
Determine the procedure for analysis for analyzing and
summarizing data
Types of Sampling Procedures
Simple random sampling: Select units out of
population such that each population unit has an equal
chance of being drawn.
Sequential sampling: Draw sample from every nth
element in the population
Stratified random sampling: divides the population of
N units into sub-populations (N1, N2, …, NL) units,
according to differences in some defining characteristics.
Random samples are then taken within each strata.
Cluster sampling: Grouping sampling units usually on a
spatial or geographic basis. Clusters are then selected at
random for sample
Determining Sample Size
Accuracy of estimates increases with the size
of the sample
Degree of accuracy should be balanced
against the cost of survey sampling
Determination of sample size involves two
major steps:
1. Make assumption about the population
distribution
2. Make decision about the acceptable limits of
error
The Normal Distribution
Normal Distribution is defined by:
1.
The Mean: μ
2.
The Standard deviation: σ
Probability of occurrence is measured by the
surface area under curve.
Confidence Level
Level of confidence (1-α): reflects the
percentage of samples falling within the
desired limit of error.
Sample Size
n=
[z
1-α
.σ
]²
d
Where:
n = sample size
d = tolerable margin of error of mean value
σ = standard deviation of population distribution
α = fraction of area under Normal curve representing event
NOT within confidence level
z1-α = Standard normal statistics corresponding to the
(1- α) confidence level
Data Collection Survey Techniques
1. Street Inventory
2. Household Travel Behavior
3. Automatic Traffic Count
4. Manual Classification Count
5. Turning Movement Count
6. Speed Survey
7. Origin-Destination Survey
a- Roadside interviews
b- Self-completion form
c- Vehicle plate number
Street /Highway Inventory
The inventory covers:
 street name, classification
 transit route & bus stops
 abutting land uses and
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driveways
lighting
curb parking conditions
right-of-way utilization (lanes,
sidewalk, pavement,
medians)
traffic flow directions
traffic signs details
traffic signal details
traffic safety devices
Household Survey
Very important in urban transportation planning
Provide timely data on socioeconomic
characteristics and travel behavior
Three basic techniques:
1. personal interviews: Best way of getting info.
personal interaction, high response rate, time
consuming, expensive
2. telephone interviews
3. mail survey
HH survey Data
Some of HH Records
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address
no of persons>5years
genders
total trips made
motorized vs. nonmotorized
persons employed
occupation
income
drivers status
no. of cars
Some Person Records
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Age, gender
Occupation, industry, income
Trip made
Origins and destinations made
Purpose “from”
Purpose “to”
Starting time of each trip
Arrival time of every trip
Mode of travel
No. of persons in car
Kind of parking
Principal route of travel
Automatic Traffic Count ATC
Mechanically
measure volumes
Some types:
Pressure tube (hose)
Magnetic (inductive)
Radar
Video image
processing
Temporary
Permanent
Totals
16038
100.0%
Hourly Flow:
•Traffic pattern
Peak hour determination
Average daily traffic ADT
8.0%
7.0%
6.0%
5.0%
4.0%
3.0%
2.0%
1.0%
0.0%
1:
0
2: 0
0
3: 0
0
4: 0
0
5: 0
0
6: 0
0
7: 0
0
8: 0
0
9: 0
10 00
11: 00
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12 00
13: 00
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14 00
15: 00
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16 00
17: 00
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18 00
19: 00
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20 00
21: 00
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24 23: 0
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0:
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%
1.1%
0.8%
0.5%
0.4%
0.5%
0.8%
4.2%
7.5%
7.1%
6.3%
6.7%
6.2%
6.2%
5.8%
6.7%
6.4%
6.2%
5.7%
5.5%
4.8%
3.9%
3.1%
2.3%
1.6%
% of Daily Volume
Time Volume
1:00 179
2:00 121
3:00
83
4:00
61
5:00
80
6:00 127
7:00 674
8:00 1203
9:00 1131
10:00 1007
11:00 1077
12:00 1001
13:00 988
14:00 925
15:00 1069
16:00 1028
17:00 989
18:00 920
19:00 876
20:00 765
21:00 630
22:00 492
23:00 362
24:00 251
Hour of Day
Manual Classification Count MCC
Carried out for short
period of time
Normally 15-mn
interval
Classify traffic into
vehicle classes: cars,
taxi, vans, pickup,
truck, trailer, bus, etc.
Counting techniques:
1. Five-bar gate on
paper
2. Tally counter
3. Hand-held electronic
machines
CLASSIFICATION COUNT
Mar Mekhayel
1.1%
2.4%
6.0%
3.8%
Private Car
Taxi
Mini Bus / Van
Pick Up
Others
Truck
Standard Bus
11.3%
58.4%
17.3%
Turning Movement Count TMC
Manual count
carried out with:
1. Five-bar gate on
paper
2. Tally counter
3. Hand-held electronic
machines
Turning Movement Count TMC
Carried out at junctions
during peak periods
15-minute intervals
Record directional
volumes
Sometimes classify the
turning vehicles
(especially left turns into
light and heavy vehicles)
Very important for
junction operation
analysis
Speed Survey
Three types:
1. Spot speed for
individual vehicles
using “radar gun”.
2. Vehicle in the traffic
flow traveling a
certain distance using
in-vehicle measuring
equipment
3. Speed of Journey
Time Vs. Space Mean Speed
Time Mean Speed
Is the average speed of
vehicles passing a point
over a specific time
period.
Space Mean Speed
Is the average speed of
vehicles traveling over a
measured distance.
V=Σt Vt/n
Where:
V = time mean speed
Vt = speed of individual
vehicle
n = number of vehicles
observed
V=nL/Σi Ti
Where:
V = space mean speed
ti = travel time of the ith
vehicle
n = number of vehicles
observed
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Origin-Destination
Survey
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Ask drivers the origin
and destination of
their trips.
Sample-based survey
Selection of unbiased
sample
Define Traffic Analysis
Zones TAZs, cordons,
and screen lines
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O-D Survey Techniques
Roadside Interview:
- drivers are stopped at the side of the road
- Take safety measures during survey
Self-Completion Forms:
- Usually performed via mail
- Easier, but sample may not be
representative.
License Plate Survey:
- Record portion (or all) license plate number
and time at some stations
- Match license number to determine the
origin, destination and path of the vehicle