Mode Choice

Once all of the activity location choices have been calibrated the next step is to work on the mode choice model. If you are not familiar with GTAMode's mode choice model you can find its documentation here.

Parameter Locations

GTAModel V4.1

To edit the mode choice parameters in GTAModel V4.1, you will directly change the parameters within the model system. The modes are located in three places in the model system, Auto Mode, Other Modes, and Shared Modes.

GTAModel V4.0

For GTAModel V4.0, the mode choice parameters are loaded in from EstimationResult/ModeChoice/EstimationResults.csv. Inside of the EstimationResults.csv file are a series of rows containing the estimated parameters for the mode choice model. The first row contains a header with the generation the parameter set was from, its fitness value, and continuing with all of the parameter paths (module names separated by '.'s, with the final segment being the name of the parameter). Only the second row will be used for the parameter values.

Calibration Steps

The first the to calibrate the mode choice model is to modify the modal constants to balance the number of trips by mode globally. In TMG provided GTAModels the Auto mode will have its constants fixed to zero. In order to avoid parameter scaling, please leave this mode with zero constants. Each mode has size constants, one for each person category, and a constant for an intrazonal trip. The intrazonal constant is additive to the appropriate person category.

After the modes are balanced globally the next step is to add/modify the Time Period Constants. If the time period has not already been added you will need to do so. Make sure to set the start and end time parameters to match the time period by changing the parameters of the module accordingly. Given the correct time period, check the Spatial Constants to see if a parameter already exists for the OD that you wish to modify. All modifications are done at a planning district to planning district level. For these parameters it is traditional to use the format 1-4,6:5,7-16 where the colon breaks up the two range sets, on the left the origin and on the right hand side the destination range set. If you add additional calibration constants make sure that if you add OD's that overlap that the more specific term comes first in the list or it will be ignored as the first module that satisfies the criteria will be selected.

Tip

When working with the Time Period Constants remember that by modifying a parameter in any time period, the chosen modes in the other time periods will also be modified as tours containing the modified mode will now be more attractive.