The New Network Calculator

One of the most important new developments in Release 5.0 is certainly the implementation of the new Network Calculator , module 2.41. While remaining fully upward compatible with the previous versions of this module, the functionality has been greatly enhanced. Since all the new features are described in detail in the Release Notes and the new User's Manual, we shall limit the discussion here to outlining briefly the main new features and options - without going into any technical details.

The following is a short summary of the main new features and enhancements of the Network Calculator:

• Transit segment and transit line attributes are now fully integrated into the calculator functions. Transit line and segment attributes can be accessed and modified according to the usual rules.
• Automatic inheritance of attributes of dependent elements is available at all levels. This implies that within a transit segment expression, all i-node, j-node, link and line attributes can be used. They refer to the attribute values of the corresponding i-node, j-node, link and line that are associated with each transit segment. Attributes of the transit vehicle type can be accessed as if they were read-only transit line attributes.
• Result aggregation to any type of element is supported. The aggregation operator can be chosen as minimum, maximum, average, sum, bitwise AND and bitwise OR. E.g. the result of a computation at the segment level can be aggregated per line, link, i-node or j-node.
• The options for copying an attribute from an other scenario and importing from an external file have been enhanced to handle transit line and transit segment attributes, as well as node and link data.
• All transit segment attributes of the next segment (along the itinerary) can be accessed directly within an expression. This allows computations that involve not only one segment at a time, but which relate to the order of the segments or stops along the itinerary.
• All attributes of the reverse link can now be accessed directly within an expression. With this new feature, computations can be carried out which relate the attributes of a link in both directions.
• The link attribute modes can now be modified with the Network Calculator. This is done by specifying MODES as the attribute to save the result in. Instead of entering an expression, the user is then prompted to define the mode change he wants to perform and to which subset of links this change should be applied.
• Intermediary results from all operations (i.e. calculations, copying from other scenarios or importing from an external file) can now be stored in temporary attributes. Up to 9 temporary attribute vectors are available for each type of element. Thus, it is no longer necessary to sacrifice one of the three user data items when intermediary results need to be stored. The temporary attributes created in this way will stay available for further computations within the same module call, they are only discarded once module 2.41 is left. This new feature removes the main bottleneck that is associated with the limit of having only 3 user data items per element and scenario.
• Special index attributes allow accessing of the internal ordering of the elements in the data base. For transit lines this is especially useful since it allows line enumeration in a macro, even if the line names are not known explicitly. For transit segment computations, this feature allows to locate a segment within the itinerary and, combined with the access of next segment attributes, allows the writing of macros that perform complex computations on transit line itineraries.

The wealth of new features in the Network Calculator included in Release 5.0 will undoubtedly give rise to many new and novel applications. Even if most of the developments are related to transit, there are many new possibilities that will benefit non-transit applications as well: temporary attributes, reverse link attributes and mode modifications, to name just a few.

For transit application the new Network Calculator opens an entirely new world of possible new applications. They range from the comparison of on board counts, over the automatic adjustment of line headways, up to implementing a complete congested transit assignment. In future issues of EMME/2 NEWS we will report on some of these possibilities in more detail.