In most cases you will want to apply the same model calculation to several or all scenarios in order to compare the results. By default, Visum uses the procedure parameters of the base version to calculate a scenario. To specify the calculation sequence, in the Project view, click the Edit base version button. Then, under Procedure sequence, choose the sequence in which you want the operations performed.
Some operations require reading or writing access to files, e.g. to externally saved skim matrices or filter files. Under Project view, you specify whether Visum has access to one file for the entire project or to file copies of the respective scenarios. You can specify this for all files of a certain type or globally for the entire project.
However, sometimes you might want to use a different calculation sequence for a scenario than the default one, e.g. when you want to vary the procedure parameters. In this case, define a variable for the procedure parameter set of the base version. The definition of the variables contains a reference to the procedure and the respective parameter, e.g. to the coefficient of the fare or toll that represent the time values applied (value of time). On the Scenarios tab of the project, a column is created for the variable. In the column, you can specify a value for each scenario (Using Visum: Creating scenarios with different variable allocations). Variables are always part of a procedure parameter set, i.e. the variable value can only be defined for a scenario if the corresponding procedure parameter set is used. If these are parameters of the general procedure settings, create a new procedure parameter set with changed settings based on the procedure parameters of the base version. Allocate one set of procedure parameters stored in the project to each scenario. When a scenario is calculated, the set of procedure parameters including the parameters defined by variable values is saved in the result version.
