Urban Transportation Planning-4

7/30/2019 Urban Transportation Planning-4

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Urban Transportation Planning -4

Dr. Muhammad Adnan


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Cross Classification Models(Trip Generation Stage)


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Definition

Category Analysis/Cross Classification

It is based on estimating the response (e.g.

No. of trips per household for a given

purpose) as a function of household

attributes.

Based on the assumption that trip generation

rates are relatively stable over time for certain

household stratifications.


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Example of cross classification model


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Model Specification

Cross classification is based on grouping the households in different strata;

for example, a specific cell is based on household size and household

income.

The trip production rate for that specific cell then is total number of trips

in that cell divided by the number of household in that cell.


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Categories basis

Choice of categories is based on the notion that trip

rate distribution for a particular household type have

its standard deviation as minimum as possible.


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Advantages of the Method

Cross-classification groupings are independent of the

zone system of the study area.

No prior assumptions about the relationship are

required (i.e. they dont even have to be monotonic,let alone linear)

Relationship can differ in form from class to class

(e.g. the effect of changes in household size for one

or two car-owning households may be different.)


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Disadvantage of the method

It does not permit extrapolation beyond its calibration strata.

There are no statistical goodness-of-fit measure for themodel.

It requires large sample sizes (25 household per cell);

otherwise cell values will vary in reliability. There is no effective way to choose among variables for

classification, or choose best groupings of a given variable;the minimization of st. deviation process requires anextensive trial and error procedure which may be consideredinfeasible in practical studies.

If it is required to increase the number of stratifying variables,it might be necessary to increase the sample enormously.


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Attraction Models (Example)

Attraction per EmployeeRetail Government Services Private Services

1.36 1.2 1.9

HBW TRIPS


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Questions (1)

The following table presents the data collected in the last household survey

(ten years ago) for three particular zone.

Zone 1, 2.0 r/HH, 1.0 W/hh, 50000 MI, 20000 P

Zone 2, 3.0 r/HH, 2.0 W/hh, 70000 MI, 60000 P

Zone 1, 2.5 r/HH, 2.0 W/hh, 100000 MI, 100000 P

Y=0.2 +0.5x1+1.1Z1; R-square=0.78

X1 = Number of workers in the household

Z1= dummy variable which is 1 for high income (>70,000) otherwise zero

Faimlystructure

INCOME

LOW HIGH

1 or less 0.8 1.0

2 or more 1.2 2.3

If the total number of trips aregenerated today during peak hour

By the three zones are, 8200,24300

And 92500 respectively, which model is

Best. Explain your answer


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Questions (2)

Given the following data, create a trip

generation model using EXCEL to perform

linear least square multiple regression.

What is wrong with using all "independent"

variables at one time?

Which independent variable is best? Explain.

If you see there is non-linear (y=axb)

relationship with a independent variable how

you will perform your regression analysis.


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Balancing Trip Productions and Attractions


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Urban Transportation Planning-4