Modal Split Analysis

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Modal Split Analysis
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Modal Split Analysis

• This phase of travel-demand forecasting, we
  analyze peoples decision regarding mode of
  travel auto, bus, jeepneys, train, and so on,
  are analyzed
• Mode usage analysis can be done at various
  points in the forecasting process
• The most common point is after trip distribution
  because the information on where trips are going
  allows the mode usage relationship to compare the
  alternative transportation services competing for
  users

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Three broad categories of factors that affect the
choices that people make are 1. The
characteristics of the trip makers (e.g. family
income, number of autos available, family size,
residential density) 2. The characteristics of
the trip (e.g. trip distance, time of day) 3. The
characteristics of the transportation system
(e.g. riding time, excess time)
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•  Logit Model
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• The logit formulation is a share model that
  divides the persons between the various modes
  depending on each modes relative desirability
  for any given trip.
• Modes are said to be relatively more desirable
  if they are faster, cheaper, or have other mode
  favorable features than competitive modes
• The better a mode is, the more utility it has
  for the potential traveler.

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• The logit model takes the following form to
  trade off the relative utilities of various
  modes
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• Probability of using mode i, Pi, is given by

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Example
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Hence, even a flat parking of 1.00 makes a 5
difference in automobile ridership.
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Estimating the Utility Functions of Choice
Models, Maximum Likelihood Method
Example Suppose a logit model of choice between
the modes automobile and bus is being developed.
The only variable of the model is total travel
time, T. The deterministic component of the
models utility function is specified as   V
aT   where a is a constant coefficient.
Let the choices and travel times for the
individuals in the estimation sample be
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where L is called the sample likelihood
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Example A mode-choice model for a city includes
the following modes autos (A), light rail (L),
buses (B), and rapid rail (R), with utility
functions (U), as shown in the table
where C is the cost in dollars, and T is the time
in minutes.

1. Based on an estimate that 12,000 workers will
   head for downtown each morning, how many workers
   will choose to take a particular mode/
2. If the government subsidizes light rail by 30,
   buses by 20, and rail rapid by 10, and at the
   same time increases automobile costs by 15, what
   will be the new modal distribution/

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Example A city has a utility function for use in
a logit model of the form U -0.075A 0.05W
0.04R 0.02C where A is the access time in
minutes, W is the waiting time in minutes, R is
the riding time in minutes, and C is the
out-of-pocket cost in cents. (a) What modal
distribution would you expect, using the
following values for A, W, R, and C, for the four
modes used in the city.
Mode A W R C
Auto 6 1 25 300
Rail 7 10 15 75
Bus 10 15 35 60
Bike 1 0 45 10
(b) The city is seriously thinking of subsidizing
rail and bus by 50, encouraged biking by
constructing bike paths and thus reducing biking
time by 20, and increasing auto costs (through
higher parking charges) by 10. What is likely to
be the new modal distribution with these charges?