Fundamentals of Transportation/Mode Choice/Solution

TProblem
Problem:

You are given the following mode choice model.

U_{ijm} = -1 C_{ijm} + 5 D_T\,\!

Where:

  • C_{ijm} = travel cost between i and j by mode m
  • D_T = dummy variable (alternative specific constant) for transit
Auto Travel Times
Origin\Destination Dakotopolis New Fargo
Dakotopolis 5 7
New Fargo 7 5
Transit Travel Times
Origin\Destination Dakotopolis New Fargo
Dakotopolis 10 15
New Fargo 15 8
Example
Solution:

Part A

A. Using a logit model, determine the probability of a traveler driving.

Solution Steps

  1. Compute Utility for Each Mode for Each Cell
  2. Compute Exponentiated Utilities for Each Cell
  3. Sum Exponentiated Utilities
  4. Compute Probability for Each Mode for Each Cell
  5. Multiply Probability in Each Cell by Number of Trips in Each Cell


Auto Utility: U_{auto}
Origin\Destination Dakotopolis New Fargo
Dakotopolis -5 -7
New Fargo -7 -5
Transit Utility: U_{transit}
Origin\Destination Dakotopolis New Fargo
Dakotopolis -5 -10
New Fargo -10 -3


e^{U_{auto}}
Origin\Destination Dakotopolis New Fargo
Dakotopolis 0.0067 0.0009
New Fargo 0.0009 0.0067
e^{U_{transit}}
Origin\Destination Dakotopolis New Fargo
Dakotopolis 0.0067 0.0000454
New Fargo 0.0000454 0.0565


Sum: e^{U_{transit}} + e^{U_{auto}}
Origin\Destination Dakotopolis New Fargo
Dakotopolis 0.0134 0.0009454
New Fargo 0.0009454 0.0498


P(Auto) =  e^{U_{auto}}/(e^{U_{auto}} + e^{U_{transit}})
Origin\Destination Dakotopolis New Fargo
Dakotopolis 0.5 0.953
New Fargo 0.953 0.12
P(Transit) =  e^{U_{transit}}/(e^{U_{auto}} + e^{U_{transit}})
Origin\Destination Dakotopolis New Fargo
Dakotopolis 0.5 0.047
New Fargo 0.047 0.88

Part B

B. Using the results from the previous problem (#2), how many car trips will there be?

Recall

Total Trips
Origin\Destination Dakotopolis New Fargo
Dakotopolis 9395 5606
New Fargo 6385 15665
Total Trips by Auto = T_{ij}*P(Auto)
Origin\Destination Dakotopolis New Fargo
Dakotopolis 4697 5339
New Fargo 6511 1867
Last modified on 25 July 2008, at 17:39