Pekol (Transport Demand Modelling - Trip Generation)

Question 1

What is the 4-Step transport model?

Answer 1

Land Use Data + Travel Data + Zones & Network
>Trip generation
>Trip distribution
>Modal split
>Assignment

Question 2

What question does trip generation attempt to answer?

Answer 2

How many trips start and end in a zone

Question 3

What is a Home Based (HB) trip?

Answer 3

A trip with one end at home

Question 4

What is a Non Home-Based (NHB) trip?

Answer 4

A trip with neither end at home

Question 5

How is the trip purpose found?

Answer 5

Determined by the activity at the non-home end of a home based trip

Question 6

What percentage of trips start or end at home?

Answer 6

85%

Question 7

What is trip generation?

Answer 7

The process of estimating productions and attractions for each zone in the model

Question 8

What are some trip productions?

Answer 8

• Household size

- Income and car ownership

Question 9

What are some trip attractions?

Answer 9

• Population
• Employment
• Enrolments

Question 10

What are some forms of models?

Answer 10

• Growth factor modelling
• Category analysis
• Regression analysis

Question 11

What is Category analysis?

Answer 11

• Not very popular in Aus.

- Estimates average trip rates as a function of household attributes (uses 3*3 matrix)

Question 12

What does growth factor modelling rely on?

Answer 12

Pre-existing estimate of productions and some measures of growth

Question 13

When is growth factor modelling appropriate?

Answer 13

• developed areas
• short term forecasts (<3years)
• external trips

Question 14

What is the formula for Growth factor modelling?

Answer 14

Ti=Fi*ti
Where:
Ti=future trips to/from zone
ti=existing trips to/from zone
Fi=growth factor

Question 15

What is Regression analysis?

Answer 15

A dependant variable (e.g attractions) is estimated from a set of independent variables (e.g population,employment)

Question 16

What does a zonal based regression deal with?

Answer 16

Zonal total trip ends

>there is one regression equation per trip purpose

Question 17

What does a Household based regression deal with?

Answer 17

Household trip ends

Attempts to find trips per individual household

Question 18

Wht are the benefits of Household Based Regression?

Answer 18

• Fewer independent variables give better relationship forms

- Relationships tend to be geographically and temporally stable

Question 19

What is a disadvantage of Household based regression?

Answer 19

Greater variation between households.

Due to huge variation in input data, lower R^2 values

Question 20

What are the key components of Dummy Variable regression?

Answer 20

• Dummy variables take on value 0 or 1 (e.g smoker=1, non-smoker=0)
• Captures non-linearity between trip rates and independent variables
• Developed at the household level, but applied at the zonal level

Question 21

Why do we need the attractions to equal productions?

Answer 21

• Conservation of matter (trips)

- Trip distribution (the next step)

Question 22

How do we account for the fact that attractions do not always equal productions?

Answer 22

Pragmatic solution is to factor attractions by f.

Question 23

What are some implementation issues?

Answer 23

• we assume that model parameters do not change with time (once calibrated, model coefficients remain constant)
• Often assumed to be geographically stable
• Challenge remains to forecast the various input variables
• Trip generation models ignore the impacts of transport supply, congestion and accessibility on tip makings (i.e. nothing relates to transport network itself)

Question 24

What is a major disadvantage of the four-step process?

Answer 24

• the network has no effect on trip generation

- Unlikely to be true for discretionary trips

Question 25

What is a possible solutions to change the four-step method from not having the network affect trip generation?

Answer 25

Incorporate accessibility into trip generation model.

research has found that accessibility is not significant in aggregate models

Question 26

What is activity modelling?

Answer 26

• Treat travel as part of set of wider household activities

- Activities are categorised by “need” or “function”

Question 27

Are production and attraction the same as origin and destination?

Answer 27

NO. No. No NO NO NO.