Norman Washington Garrick CE 2710 Spring 2014 Lecture 07 - PowerPoint PPT Presentation

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Norman Washington Garrick CE 2710 Spring 2014 Lecture 07

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Transportation Forecasting Trip Generation Norman Washington Garrick CE 2710 Spring 2014 Lecture 07 – PowerPoint PPT presentation

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Title: Norman Washington Garrick CE 2710 Spring 2014 Lecture 07


1
Transportation Forecasting Trip Generation
Norman Washington Garrick CE 2710
Spring 2014 Lecture 07
2
The Four Step Model
  • Trip Generation
  • Estimates the number of trips from given origins
    and destinations
  • Trip Distribution
  • Determines the destination for each trip from a
    given origin
  • Mode Choice
  • Determines the mode choice for each trip
  • Route Assignment
  • Determines the specific route for each trip

3
Trip Generation
  • Trip Generation model is used to estimate the
    number of person-trips that will begin or end in
    a given traffic analysis zone (TAZ)

The unit of analysis for traffic generation is
the TAZ
4
Trip Generation Developing and Using the Model
Survey Base Year Socio-economic, land use and
Trip making
5
Trip Generation Form of the Model
  • The trip generation model typically can take the
    form of
  • No. of trips Function (population, income,
    auto ownership rates)
  • The model is developed and calibrated using the
    BASE year data

6
Trip Generation Travel Survey
  • Trip Generation models are often developed from
    travel surveys.
  • These surveys are used to determine the trip
    making pattern for a sampling of households in
    the area.
  • This trip making pattern is then related to land
    use and socioeconomic factors that are considered
    to affect travel patterns
  • Common socioeconomic factors considered include
    population, income, and auto ownership rates

7
Trip Generation Trip Purpose
  • Often separate predictions are mode for different
    type of trips since travel behavior depends on
    trip purpose
  • In other words different models must be developed
    for each trip type
  • The category of trip types commonly used include
  • Work trips
  • School trips
  • Shopping trips
  • Recreational trips

8
Trip Generation Example of a Trip Generation Model
  • One way of presenting the trip generation model
    developed from a survey is as a
    cross-classification table

9
Trip Generation The Survey and The Model
Survey Base Year Socio-economic, land use And
Trip making
10
Trip Generation Trip Rates
Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates
Persons per Household Persons per Household Persons per Household Persons per Household
Type of Area Vehicles per HH 1 2,3 4 5
High Density 0
1
2
Low Density 0
1
2
11
Trip Generation Trip Rates
Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates
Persons per Household Persons per Household Persons per Household Persons per Household
Type of Area Vehicles per HH 1 2,3 4 5
High Density 0 0.6
1 1.5
2 1.8
Low Density 0
1
2
12
Trip Generation Trip Rates
Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates
Persons per Household Persons per Household Persons per Household Persons per Household
Type of Area Vehicles per HH 1 2,3 4 5
High Density 0 0.6 7.0
1 1.5 7.9
2 1.8 8.3
Low Density 0
1
2
13
Trip Generation Trip Rates
Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates
Persons per Household Persons per Household Persons per Household Persons per Household
Type of Area Vehicles per HH 1 2,3 4 5
High Density 0 0.6 2.1 4.6 7.0
1 1.5 3.0 5.5 7.9
2 1.8 3.4 5.9 8.3
Low Density 0
1
2
14
Trip Generation Trip Rates
Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates Total Home-Based-Non-Work Trip Rates
Persons per Household Persons per Household Persons per Household Persons per Household
Type of Area Vehicles per HH 1 2,3 4 5
High Density 0 0.6 2.1 4.6 7.0
1 1.5 3.0 5.5 7.9
2 1.8 3.4 5.9 8.3
Low Density 0 1.0 2.5 5.0 7.4
1 1.9 3.5 6.0 8.4
2 2.3 3.9 6.4 9.0
15
Trip Generation Estimating Target Year Data
16
Trip Generation Target Year Data
Number of Households in Target Year Number of Households in Target Year Number of Households in Target Year Number of Households in Target Year Number of Households in Target Year Number of Households in Target Year
Persons per Household Persons per Household Persons per Household Persons per Household
Type of Area Vehicles per HH 1 2,3 4 5
High Density 0
1
2
Low Density 0
1
2
17
Trip Generation Target Year Data
Number of Households in Target Year Number of Households in Target Year Number of Households in Target Year Number of Households in Target Year Number of Households in Target Year Number of Households in Target Year
Persons per Household Persons per Household Persons per Household Persons per Household
Type of Area Vehicles per HH 1 2,3 4 5
High Density 0 100 200 100 100
1 200 300 200 100
2 100 200 100 200
Low Density 0
1
2
18
Trip Generation Target Year Data
Number of Households in Target Year Number of Households in Target Year Number of Households in Target Year Number of Households in Target Year Number of Households in Target Year Number of Households in Target Year
Persons per Household Persons per Household Persons per Household Persons per Household
Type of Area Vehicles per HH 1 2,3 4 5
High Density 0 100 200 100 100
1 200 300 200 100
2 100 200 100 200
Low Density 0 50 100 100 100
1 100 200 100 100
2 100 100 100 10
19
Trip Generation Predicting Number of Trips
20
Trip Generation Predicting Number of Trips
Number of Trips in Target Year for Each HH Type Number of Trips in Target Year for Each HH Type Number of Trips in Target Year for Each HH Type Number of Trips in Target Year for Each HH Type Number of Trips in Target Year for Each HH Type Number of Trips in Target Year for Each HH Type
Persons per Household Persons per Household Persons per Household Persons per Household
Type of Area Vehicles per HH 1 2,3 4 5
High Density 0
1
2
Low Density 0
1
2
60
Number of Trips trip rateno. of HH 0.6 100
60
21
Trip Generation Predicting Number of Trips
Number of Trips in Target Year for Each HH Type Number of Trips in Target Year for Each HH Type Number of Trips in Target Year for Each HH Type Number of Trips in Target Year for Each HH Type Number of Trips in Target Year for Each HH Type Number of Trips in Target Year for Each HH Type
Persons per Household Persons per Household Persons per Household Persons per Household
Type of Area Vehicles per HH 1 2,3 4 5
High Density 0 60 420 460 700
1 300 900 1100 790
2 180 680 590 1660
Low Density 0 50 250 500 740
1 190 700 600 840
2 230 390 640 90
22
Trip Generation Planning for the Future and
Uncertainties
  • Earlier we talked about the uncertainties
    associated with making prediction for the future
    and the importance of not treating predictions as
    if they are set in stone but rather as a guide to
    help in decision making
  • In considering the trip generation process it
    is important to understand some potential sources
    of uncertainties

23
Trip Generation Sources of Uncertainties in
Predicting Number of Trips
  • Significant errors can creep into the trip
    generation process in a number of places
    including
  • Errors in the survey
  • Who is surveyed, how well was the survey
    constructed, did we consider all important
    parameters?
  • Errors in the prediction of future demographics
  • Will the population grew, what will be the make
    up of the population
  • Errors in how well the model can actually reflect
    the future
  • Will the land use change, will transportation
    change, will technology change, will peoples
    attitudes change

24
Trip Generation Effect of Changes in Land Use
  • Changes in Land use and the type of
    transportation provided can have a huge impact on
    travel
  • But the trip generation process typically assume
    that this factor is constant over the period of
    the study

25
Trip Generation Demographics and Trip Making
Factors affected by Land Use
  • The land use pattern and transportation type may
    affect
  • Car ownership rates
  • Household size and composition
  • Number of daily trips
  • Mode of trips
  • Length of trips
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