Even in previous releases it was possible to compute class specific volumes for a multiclass auto assignment. But as this had to be done using an additional options assignment, getting the volumes for a specific class was a rather complicated and lengthy task. And getting the class specific volumes for all classes even implied redoing the entire assignment once for each class.
In Release 8, class specific volumes can be obtained as an optional, but direct result of the multiclass assignment. For each class, the user can specify extra attributes where the corresponding class specific link and turn volumes will be saved. As these volumes are obtained directly from the master assignment, the overhead for storing them is almost nil compared to the old method of recomputing them via the additional options.
Pointers to the extra attributes containing the class specific volumes are stored in the scenario parameters. This way, the system knows for each scenario which volumes were saved in which extra attributes. This information is displayed in the assignment summaries and is also available when displaying class specific volumes in module 6.12.
In order to avoid introducing any incompatibilities to existing macros,
the storing of the class specific volumes is activated by a new 5th
option in the single class/multiclass select question, which now becomes:
Select: 1= single class assignment on auto mode
2= single class assignment with generalized cost
3= multiclass assignment
4= multiclass assignment with generalized cost
5= generalized cost multiclass assignment with class specific volumes
Note that, even if the new option mentions ``generalized cost'', if no fixed cost attributes are specified a standard time-only based multiclass assignment is obtained.
While saving class specific volumes in a multiclass assignment, the two new internal file 98 and 99 are used to store the class specific extreme point volumes generated during one iteration. For existing data banks, these files can be added ``on the fly'' when using this new feature for the first time. When creating new data banks, the user is asked if he wants to include these temporary files in the data bank or not.