1. Modal Split Analysis

2. Modal Split Analysis
This phase of travel-demand forecasting, we analyze people’s 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

3. 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)

4.  Logit Model
The logit formulation is a share model that divides the persons between the various modes depending on each mode’s 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.

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

6. Example:

10. Hence, even a flat parking of $1
Hence, even a flat parking of $1.00 makes a 5% difference in automobile ridership.

11. 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 model’s 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:

13. where
L is called the sample likelihood

16. 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.
Based on an estimate that 12,000 workers will head for downtown each morning, how many workers will choose to take a particular mode/
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/

17. Example:
A city has a utility function for use in a logit model of the form
U = A – 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 35 60
Bike 45
(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?