CE 341 Transportation Planning

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CE 341 Transportation Planning

• Data Management Diagnosis

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Transport Planning Database

• Foundation of effective Transportation Planning
• Objectives of Collecting data
• 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)

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Traffic Study Data

• Traffic studies consist of 3 primary activities
• Data Collection Observing, gathering and
  recording data.
• Data Reduction Coding, data entry, and
  tabulation.
• Data Analysis Processing of data to understand
  the observed situation, diagnosis, and plan
  improvements.

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Types of Traffic Data

• 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
• Accident data - Parking studies
• Pedestrian studies - Goods movement transit
  studies

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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
• 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

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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

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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
• Make assumption about the population distribution
• Make decision about the acceptable limits of
  error

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The Normal Distribution

• Normal Distribution is defined by
• The Mean µ
• The Standard deviation s
• Probability of occurrence is measured by the
  surface area under curve.

9
Confidence Level

• Level of confidence (1-a) reflects the
  percentage of samples falling within the desired
  limit of error.

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Sample Size

• n z1-a . s²
• d
• Where
• n sample size
• d tolerable margin of error of mean value
• s standard deviation of population distribution
• a fraction of area under Normal curve
  representing event NOT within confidence level
• z1-a Standard normal statistics corresponding
  to the (1- a) confidence level

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Data Collection Survey Techniques

• Street Inventory
• Household Travel Behavior
• Automatic Traffic Count
• Manual Classification Count
• Turning Movement Count
• Speed Survey
• Origin-Destination Survey
• a- Roadside interviews
• b- Self-completion form
• c- Vehicle plate number

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Street /Highway Inventory

• The inventory covers
• street name, classification
• transit route bus stops
• abutting land uses and 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

13
Household Survey

• Very important in urban transportation planning
• Provide timely data on socioeconomic
  characteristics and travel behavior
• Three basic techniques
• personal interviews Best way of getting info.
  personal interaction, high response rate, time
  consuming, expensive
• telephone interviews
• mail survey

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HH survey Data

• Some of HH Records
• address
• no of personsgt5years
• genders
• total trips made
• motorized vs. non-motorized
• persons employed
• occupation
• income
• drivers status
• no. of cars

• Some Person Records
• 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

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Automatic Traffic Count ATC

• Mechanically measure volumes
• Some types
• Pressure tube (hose)
• Magnetic (inductive)
• Radar
• Video image processing

Temporary Permanent
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Hourly Flow

• Traffic pattern Peak hour determinationAverage
  daily traffic ADT

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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
• Five-bar gate on paper
• Tally counter
• Hand-held electronic machines

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Turning Movement Count TMC

• Manual count carried out with
• Five-bar gate on paper
• Tally counter
• Hand-held electronic machines

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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

20
Speed Survey

• Three types
• Spot speed for individual vehicles using radar
  gun.
• Vehicle in the traffic flow traveling a certain
  distance using in-vehicle measuring equipment
• Speed of Journey

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Time Vs. Space Mean Speed

• Time Mean Speed
• Is the average speed of vehicles passing a point
  over a specific time period.
• VSt Vt/n
• Where
• V time mean speed
• Vt speed of individual vehicle
• n number of vehicles observed

• Space Mean Speed
• Is the average speed of vehicles traveling over a
  measured distance.
• VnL/Si 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

• 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